117-544: Eating (also known as consuming ) is the ingestion of food . In biology, this is typically done to provide a heterotrophic organism with energy and nutrients and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbivores eat plants, omnivores consume a mixture of both plant and animal matter, and detritivores eat detritus. Fungi digest organic matter outside their bodies as opposed to animals that digest their food inside their bodies. For humans, eating
234-578: A gastric balloon or surgery may be performed to reduce stomach volume or length of the intestines, leading to feeling full earlier, or a reduced ability to absorb nutrients from food. Many do not realize that metabolic surgery is not only about reducing intake, it has also been shown to alter gut hormones for a period of time. Obesity is a leading preventable cause of death worldwide, with increasing rates in adults and children . In 2022, over 1 billion people lived with obesity worldwide (879 million adults and 159 million children), representing more than
351-658: A 1.67-fold greater risk of obesity compared with those without the risk allele . The differences in BMI between people that are due to genetics varies depending on the population examined from 6% to 85%. Obesity is a major feature in several syndromes, such as Prader–Willi syndrome , Bardet–Biedl syndrome , Cohen syndrome , and MOMO syndrome . (The term "non-syndromic obesity" is sometimes used to exclude these conditions.) In people with early-onset severe obesity (defined by an onset before 10 years of age and body mass index over three standard deviations above normal), 7% harbor
468-477: A BMI of 30–35 kg/m reduces life expectancy by two to four years, while severe obesity (BMI ≥ 40 kg/m ) reduces life expectancy by ten years. Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in metabolic syndrome , a combination of medical disorders which includes: diabetes mellitus type 2 , high blood pressure , high blood cholesterol , and high triglyceride levels . A study from
585-581: A branch. Those species that seek pest insects are considered beneficial 'biological control agents' and their presence encouraged in biological pest control programmes. Combined, insectivorous birds eat 400–500 million metric tons of arthropods annually. Nectar feeders such as hummingbirds , sunbirds , lories, and lorikeets amongst others have specially adapted brushy tongues and in many cases bills designed to fit co-adapted flowers. Kiwis and shorebirds with long bills probe for invertebrates; shorebirds' varied bill lengths and feeding methods result in
702-743: A diverse range of species from annelids to elephants, chimpanzees and many birds. About 182 fish consume seeds or fruit. Animals (domesticated and wild) use as many types of grasses that have adapted to different locations as their main source of nutrients. Humans eat thousands of plant species; there may be as many as 75,000 edible species of angiosperms , of which perhaps 7,000 are often eaten. Plants can be processed into breads, pasta, cereals, juices and jams or raw ingredients such as sugar, herbs, spices and oils can be extracted. Oilseeds are pressed to produce rich oils – sunflower , flaxseed , rapeseed (including canola oil ) and sesame . Many plants and animals have coevolved in such
819-570: A double of adult cases (and four times higher than cases among children) registered in 1990. Obesity is more common in women than in men. Today, obesity is stigmatized in most of the world. Conversely, some cultures, past and present, have a favorable view of obesity, seeing it as a symbol of wealth and fertility. The World Health Organization , the US, Canada, Japan, Portugal, Germany, the European Parliament and medical societies, e.g.
936-412: A drop in cellular lipid levels (lipoprivation). Both the brain and the liver monitor the levels of metabolic fuels. The brain checks for glucoprivation on its side of the blood–brain barrier (since glucose is its fuel), while the liver monitors the rest of the body for both lipoprivation and glucoprivation. There are short-term signals of satiety that arise from the head, the stomach, the intestines, and
1053-671: A greater prevalence of labor-saving technology in the home. In children, there appear to be declines in levels of physical activity (with particularly strong declines in the amount of walking and physical education), likely due to safety concerns, changes in social interaction (such as fewer relationships with neighborhood children), and inadequate urban design (such as too few public spaces for safe physical activity). World trends in active leisure time physical activity are less clear. The World Health Organization indicates people worldwide are taking up less active recreational pursuits, while research from Finland found an increase and research from
1170-583: A high protein, fibre, vitamin E and B content. Seeds are a good source of food for animals because they are abundant and contain fibre and healthful fats, such as omega-3 fats . Complicated chemical interactions can enhance or depress bioavailability of certain nutrients. Phytates can prevent the release of some sugars and vitamins. Animals that only eat plants are called herbivores , with those that mostly just eat fruits known as frugivores , leaves, while shoot eaters are folivores (pandas) and wood eaters termed xylophages (termites). Frugivores include
1287-586: A high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity. In 2007 repeating the same research found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of globalization . Among developed countries, levels of adult obesity, and percentage of teenage children who are overweight, are correlated with income inequality . A similar relationship
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#17327803655611404-757: A lack of physical activity as the cause of most cases of obesity. A limited number of cases are due primarily to genetics, medical reasons, or psychiatric illness. In contrast, increasing rates of obesity at a societal level are felt to be due to an easily accessible and palatable diet, increased reliance on cars , and mechanized manufacturing. Some other factors have been proposed as causes towards rising rates of obesity worldwide, including insufficient sleep , endocrine disruptors , increased usage of certain medications (such as atypical antipsychotics ), increases in ambient temperature, decreased rates of smoking , demographic changes, increasing maternal age of first-time mothers, changes to epigenetic dysregulation from
1521-564: A lower BMI than Caucasians , some nations have redefined obesity; Japan has defined obesity as any BMI greater than 25 kg/m while China uses a BMI of greater than 28 kg/m . The preferred obesity metric in scholarly circles is the body fat percentage (BF%) – the ratio of the total weight of person's fat to his or her body weight, and BMI is viewed merely as a way to approximate BF%. According to American Society of Bariatric Physicians , levels in excess of 32% for women and 25% for men are generally considered to indicate obesity. BMI
1638-424: A majority of people living with obesity at any given time attempt to lose weight and are often successful, maintaining weight loss long-term is rare. There is no effective, well-defined, evidence-based intervention for preventing obesity. Obesity prevention requires a complex approach, including interventions at medical, societal, community, family, and individual levels. Changes to diet as well as exercising are
1755-633: A man's risk increases by 4% per child. This could be partly explained by the fact that having dependent children decreases physical activity in Western parents. In the developing world urbanization is playing a role in increasing rate of obesity. In China overall rates of obesity are below 5%; however, in some cities rates of obesity are greater than 20%. In part, this may be because of urban design issues (such as inadequate public spaces for physical activity). Time spent in motor vehicles, as opposed to active transportation options such as cycling or walking,
1872-507: A meal. The control of food intake is a physiologically complex, motivated behavioral system. Hormones such as cholecystokinin , bombesin , neurotensin , anorectin , calcitonin , enterostatin , leptin and corticotropin-releasing hormone have all been shown to suppress food intake. Eating rapidly leads to obesity and overeating, probably because the feelings of satiety can be slower. There are numerous signals given off that initiate hunger . There are environmental signals, signals from
1989-678: A million. Herbivores generally have more than carnivores as they need to tell which plants may be poisonous. Not all mammals share the same tastes: some rodents can taste starch , cats cannot taste sweetness, and several carnivores (including hyenas , dolphins, and sea lions) have lost the ability to sense up to four of the five taste modalities found in humans. Food is broken into nutrient components through digestive process. Proper digestion consists of mechanical processes ( chewing , peristalsis ) and chemical processes ( digestive enzymes and microorganisms ). The digestive systems of herbivores and carnivores are very different as plant matter
2106-450: A multidisciplinary team rather than "eat less, move more" being the answer as for most living with obesity, diet & exercise have failed them countless times. There is now a scientific realization where 5% of people with this disease are able to lose & maintain loss through this method as the body will adapt & reach a plateau where for most, it begins to push back towards set point. Also that bodies react differently to energy. So too
2223-404: A phenomenon known as the obesity survival paradox. The paradox was first described in 1999 in overweight and obese people undergoing hemodialysis and has subsequently been found in those with heart failure and peripheral artery disease (PAD). In people with heart failure, those with a BMI between 30.0 and 34.9 had lower mortality than those with a normal weight. This has been attributed to
2340-495: A significant effect on an individual's weight. Those who quit smoking gain an average of 4.4 kilograms (9.7 lb) for men and 5.0 kilograms (11.0 lb) for women over ten years. However, changing rates of smoking have had little effect on the overall rates of obesity. In the United States, the number of children a person has is related to their risk of obesity. A woman's risk increases by 7% per child, while
2457-950: A single point DNA mutation. Studies that have focused on inheritance patterns rather than on specific genes have found that 80% of the offspring of two obese parents were also obese, in contrast to less than 10% of the offspring of two parents who were of normal weight. Different people exposed to the same environment have different risks of obesity due to their underlying genetics. The thrifty gene hypothesis postulates that, due to dietary scarcity during human evolution, people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely to survive famine . This tendency to store fat, however, would be maladaptive in societies with stable food supplies. This theory has received various criticisms, and other evolutionarily-based theories such as
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#17327803655612574-438: A social occasion. At their highest level of sophistication, these places become "theatrical spectacles of global cosmopolitanism and myth ." At picnics , potlucks , and food festivals , eating is the primary purpose of a social gathering. At many social events, food and beverages are made available to attendees. People usually have two or three meals a day. Snacks of smaller amounts may be consumed between meals. Doctors in
2691-546: A source of food for protozoa, who in turn provide a source of food for other organisms such as small invertebrates. Other organisms that feed on bacteria include nematodes, fan worms, shellfish and a species of snail. In the marine environment, plankton (which includes bacteria , archaea , algae , protozoa and microscopic fungi ) provide a crucial source of food to many small and large aquatic organisms. Without bacteria, life would scarcely exist because bacteria convert atmospheric nitrogen into nutritious ammonia . Ammonia
2808-425: A system with nineteen food classifications: cereals, roots, pulses and nuts, milk, eggs, fish and shellfish, meat, insects, vegetables, fruits, fats and oils, sweets and sugars, spices and condiments, beverages, foods for nutritional uses, food additives, composite dishes and savoury snacks. In a given ecosystem, food forms a web of interlocking chains with primary producers at the bottom and apex predators at
2925-456: A way that the fruit is a good source of nutrition to the animal who then excretes the seeds some distance away, allowing greater dispersal. Even seed predation can be mutually beneficial, as some seeds can survive the digestion process. Insects are major eaters of seeds, with ants being the only real seed dispersers. Birds, although being major dispersers, only rarely eat seeds as a source of food and can be identified by their thick beak that
3042-416: Is a carnivorous diet (and includes insectivorous diets). Other mammals, called herbivores , eat plants, which contain complex carbohydrates such as cellulose. An herbivorous diet includes subtypes such as granivory (seed eating), folivory (leaf eating), frugivory (fruit eating), nectarivory (nectar eating), gummivory (gum eating) and mycophagy (fungus eating). The digestive tract of an herbivore
3159-447: Is a fruit if the part eaten is derived from the reproductive tissue , so seeds, nuts and grains are technically fruit. From a culinary perspective, fruits are generally considered the remains of botanically described fruits after grains, nuts, seeds and fruits used as vegetables are removed. Grains can be defined as seeds that humans eat or harvest, with cereal grains (oats, wheat, rice, corn, barley, rye, sorghum and millet) belonging to
3276-537: Is a major cause of disability and is correlated with various diseases and conditions , particularly cardiovascular diseases , type 2 diabetes , obstructive sleep apnea , certain types of cancer , and osteoarthritis . Obesity has individual, socioeconomic, and environmental causes. Some known causes are diet, physical activity, automation , urbanization , genetic susceptibility , medications , mental disorders , economic policies , endocrine disorders , and exposure to endocrine-disrupting chemicals . While
3393-476: Is a medical condition, sometimes considered a disease , in which excess body fat has accumulated to such an extent that it can potentially have negative effects on health . People are classified as obese when their body mass index (BMI)—a person's weight divided by the square of the person's height—is over 30 kg / m ; the range 25–30 kg / m is defined as overweight . Some East Asian countries use lower values to calculate obesity. Obesity
3510-696: Is a sensation considered unpleasant characterised by having a sharp, pungent taste. Unsweetened dark chocolate, caffeine , lemon rind, and some types of fruit are known to be bitter. Umami, commonly described as savory, is a marker of proteins and characteristic of broths and cooked meats. Foods that have a strong umami flavor include cheese, meat and mushrooms. While most animals taste buds are located in their mouth, some insects taste receptors are located on their legs and some fish have taste buds along their entire body. Dogs, cats and birds have relatively few taste buds (chickens have about 30), adult humans have between 2000 and 4000, while catfish can have more than
3627-553: Is an indication that gut flora can affect the metabolic potential. This apparent alteration is believed to confer a greater capacity to harvest energy contributing to obesity. Whether these differences are the direct cause or the result of obesity has yet to be determined unequivocally. The use of antibiotics among children has also been associated with obesity later in life. An association between viruses and obesity has been found in humans and several different animal species. The amount that these associations may have contributed to
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3744-445: Is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin and contains essential nutrients such as carbohydrates , fats , proteins , vitamins , or minerals . The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy
3861-571: Is believed to be contributing to the rising rates of obesity and to an increased risk of metabolic syndrome and type 2 diabetes . Vitamin D deficiency is related to diseases associated with obesity. As societies become increasingly reliant on energy-dense , big-portions, and fast-food meals, the association between fast-food consumption and obesity becomes more concerning. In the United States, consumption of fast-food meals tripled and food energy intake from these meals quadrupled between 1977 and 1995. Agricultural policy and techniques in
3978-402: Is caused by acids , such as vinegar in alcoholic beverages. Sour foods include citrus, specifically lemons and limes . Sour is evolutionarily significant as it can signal a food that may have gone rancid due to bacteria. Saltiness is the taste of alkali metal ions such as sodium and potassium. It is found in almost every food in low to moderate proportions to enhance flavor. Bitter taste
4095-462: Is correlated with increased risk of obesity. Malnutrition in early life is believed to play a role in the rising rates of obesity in the developing world . Endocrine changes that occur during periods of malnutrition may promote the storage of fat once more food energy becomes available. The study of the effect of infectious agents on metabolism is still in its early stages. Gut flora has been shown to differ between lean and obese people. There
4212-731: Is drunk or processed into dairy products (cheese, butter, etc.). Eggs laid by birds and other animals are eaten and bees produce honey , a reduced nectar from flowers that is used as a popular sweetener in many cultures. Some cultures consume blood , such as in blood sausage , as a thickener for sauces, or in a cured , salted form for times of food scarcity, and others use blood in stews such as jugged hare . Animals, specifically humans, typically have five different types of tastes: sweet , sour , salty , bitter , and umami . The differing tastes are important for distinguishing between foods that are nutritionally beneficial and those which may contain harmful toxins. As animals have evolved ,
4329-502: Is harder to digest. Carnivores mouths are designed for tearing and biting compared to the grinding action found in herbivores. Herbivores however have comparatively longer digestive tracts and larger stomachs to aid in digesting the cellulose in plants. According to the World Health Organization (WHO), about 600 million people worldwide get sick and 420,000 die each year from eating contaminated food. Diarrhea
4446-469: Is host to bacteria that ferment these complex substances, and make them available for digestion, which are either housed in the multichambered stomach or in a large cecum. Some mammals are coprophagous , consuming feces to absorb the nutrients not digested when the food was first ingested. An omnivore eats both prey and plants. Carnivorous mammals have a simple digestive tract because the proteins , lipids and minerals found in meat require little in
4563-406: Is mainly composed of water, lipids , proteins , and carbohydrates . Minerals (e.g., salts) and organic substances (e.g., vitamins ) can also be found in food. Plants, algae , and some microorganisms use photosynthesis to make some of their own nutrients. Water is found in many foods and has been defined as a food by itself. Water and fiber have low energy densities, or calories , while fat
4680-425: Is more complex, but is typically an activity of daily living . Physicians and dieticians consider a healthful diet essential for maintaining peak physical condition. Some individuals may limit their amount of nutritional intake. This may be a result of a lifestyle choice: as part of a diet or as religious fasting. Limited consumption may be due to hunger or famine. Overconsumption of calories may lead to obesity and
4797-431: Is not possible, as is often the case when recovering from surgery , alternatives are enteral nutrition and parenteral nutrition . To maintain a high constant body temperature is energy expensive—mammals therefore need a nutritious and plentiful diet. While the earliest mammals were probably predators, different species have since adapted to meet their dietary requirements in a variety of ways. Some eat other animals—this
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4914-897: Is not regarded as a psychiatric disorder, and therefore is not listed in the DSM-IVR as a psychiatric illness. The risk of overweight and obesity is higher in patients with psychiatric disorders than in persons without psychiatric disorders. Obesity and depression influence each other mutually, with obesity increasing the risk of clinical depression, and also depression leading to a higher chance of developing obesity. Certain medications may cause weight gain or changes in body composition ; these include insulin , sulfonylureas , thiazolidinediones , atypical antipsychotics , antidepressants , steroids , certain anticonvulsants ( phenytoin and valproate ), pizotifen , and some forms of hormonal contraception . While genetic influences are important to understanding obesity, they cannot completely explain
5031-414: Is now viewed as outdated in numerous countries. It ignores variations between individuals in amounts of lean body mass, particularly muscle mass. Individuals involved in heavy physical labor or sports may have high BMI values despite having little fat. For example, more than half of all NFL players are classified as "obese" (BMI ≥ 30), and 1 in 4 are classified as "extremely obese" (BMI ≥ 35), according to
5148-451: Is seen among US states: more adults, even in higher social classes, are obese in more unequal states. Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for physical fitness . In undeveloped countries
5265-445: Is seen in the overweight and obese. One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event. Another study found that if one takes into account chronic obstructive pulmonary disease (COPD) in those with PAD, the benefit of obesity no longer exists. The " a calorie is a calorie " model of obesity posits a combination of excessive food energy intake and
5382-403: Is supported both by tests of people carried out in a calorimeter room and by direct observation. A sedentary lifestyle may play a significant role in obesity. Worldwide there has been a large shift towards less physically demanding work, and currently at least 30% of the world's population gets insufficient exercise. This is primarily due to increasing use of mechanized transportation and
5499-506: Is the most common illness caused by consuming contaminated food, with about 550 million cases and 230,000 deaths from diarrhea each year. Children under five years of age account for 40% of the burden of foodborne illness, with 125,000 deaths each year. A 2003 World Health Organization (WHO) report concluded that about 30% of reported food poisoning outbreaks in the WHO European Region occur in private homes. According to
5616-738: Is the most energy-dense component. Some inorganic (non-food) elements are also essential for plant and animal functioning. Human food can be classified in various ways, either by related content or by how it is processed. The number and composition of food groups can vary. Most systems include four basic groups that describe their origin and relative nutritional function: Vegetables and Fruit, Cereals and Bread, Dairy, and Meat. Studies that look into diet quality group food into whole grains/cereals, refined grains/cereals, vegetables, fruits, nuts, legumes, eggs, dairy products, fish, red meat, processed meat, and sugar-sweetened beverages. The Food and Agriculture Organization and World Health Organization use
5733-565: Is the precursor to proteins, nucleic acids, and most vitamins. Since the advent of industrial process for nitrogen fixation, the Haber-Bosch Process , the majority of ammonia in the world is human-made. Plants as a food source are divided into seeds, fruits, vegetables, legumes, grains and nuts. Where plants fall within these categories can vary, with botanically described fruits such as the tomato, squash, pepper and eggplant or seeds like peas commonly considered vegetables. Food
5850-549: Is the result of an interplay between genetic and environmental factors. Polymorphisms in various genes controlling appetite and metabolism predispose to obesity when sufficient food energy is present. As of 2006, more than 41 of these sites on the human genome have been linked to the development of obesity when a favorable environment is present. People with two copies of the FTO gene (fat mass and obesity associated gene) have been found on average to weigh 3–4 kg more and have
5967-402: Is then released, and the glucose stored as an energy reserve. Photosynthetic plants, algae and certain bacteria often represent the lowest point of the food chains, making photosynthesis the primary source of energy and food for nearly all life on earth. Plants also absorb important nutrients and minerals from the air, natural waters, and soil. Carbon, oxygen and hydrogen are absorbed from
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#17327803655616084-404: Is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food to compensate for the lack of teeth. Some species such as pigeons and some psittacine species do not have a gallbladder . Most birds are highly adapted for rapid digestion to aid with flight. Some migratory birds have adapted to use protein stored in many parts of their bodies, including protein from
6201-406: Is used to crack open the seed coat. Mammals eat a more diverse range of seeds, as they are able to crush harder and larger seeds with their teeth. Animals are used as food either directly or indirectly. This includes meat, eggs, shellfish and dairy products like milk and cheese. They are an important source of protein and are considered complete proteins for human consumption as they contain all
6318-516: Is well documented that some ungulates such as giraffes, camels, and cattle, will gnaw on bones to consume particular minerals and nutrients. Also, cats, which are generally regarded as obligate carnivores, occasionally eat grass to regurgitate indigestible material (such as hairballs ), aid with hemoglobin production, and as a laxative. Birds' diets are varied and often include nectar , fruit, plants, seeds, carrion , and various small animals, including other birds. The digestive system of birds
6435-540: The American Medical Association , classify obesity as a disease. Others, such as the UK , do not. Obesity is typically defined as a substantial accumulation of body fat that could impact health. Medical organizations tend to classify people living with obesity as based on body mass index (BMI) – a ratio of a person's weight in kilograms to the square of their height in meters . For adults,
6552-621: The Ancient Romans . Ancient Hebrews also adopted this posture for traditional celebrations of Passover . Compulsive overeating, or emotional eating , is "the tendency to eat in response to negative emotions". Empirical studies have indicated that anxiety leads to decreased food consumption in people with normal weight and increased food consumption in the obese . Many laboratory studies showed that overweight individuals are more emotionally reactive and are more likely to overeat when distressed than people of normal weight. Furthermore, it
6669-500: The Endocrine Society , there is "growing evidence suggesting that obesity is a disorder of the energy homeostasis system, rather than simply arising from the passive accumulation of excess weight". Excess appetite for palatable, high-calorie food (especially fat, sugar, and certain animal proteins) is seen as the primary factor driving obesity worldwide, likely because of imbalances in neurotransmitters affecting
6786-785: The International Association for Food Protection , the World Resources Institute , the World Food Programme , the Food and Agriculture Organization , and the International Food Information Council . Food is any substance consumed to provide nutritional support and energy to an organism . It can be raw, processed, or formulated and is consumed orally by animals for growth, health, or pleasure. Food
6903-750: The Poaceae (grass) family and pulses coming from the Fabaceae (legume) family. Whole grains are foods that contain all the elements of the original seed (bran, germ, and endosperm ). Nuts are dry fruits, distinguishable by their woody shell. Fleshy fruits (distinguishable from dry fruits like grain, seeds and nuts) can be further classified as stone fruits (cherries and peaches), pome fruits (apples, pears), berries (blackberry, strawberry), citrus (oranges, lemon), melons (watermelon, cantaloupe), Mediterranean fruits (grapes, fig), tropical fruits (banana, pineapple). Vegetables refer to any other part of
7020-496: The RAK Hospital found that obese people are at a greater risk of developing long COVID . The CDC has found that obesity is the single strongest risk factor for severe COVID-19 illness. Complications are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet or a sedentary lifestyle . The strength of the link between obesity and specific conditions varies. One of
7137-435: The World Health Organization (WHO) defines " overweight " as a BMI 25 or higher, and "obesity" as a BMI 30 or higher. The U.S. Centers for Disease Control and Prevention (CDC) further subdivides obesity based on BMI, with a BMI 30 to 35 called class 1 obesity; 35 to 40, class 2 obesity; and 40+, class 3 obesity. For children, obesity measures take age into consideration along with height and weight. For children aged 5–19,
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#17327803655617254-543: The drifty gene hypothesis and the thrifty phenotype hypothesis have also been proposed. Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes (listed above) as well as some congenital or acquired conditions: hypothyroidism , Cushing's syndrome , growth hormone deficiency , and some eating disorders such as binge eating disorder and night eating syndrome . However, obesity
7371-420: The gastrointestinal system , and metabolic signals that trigger hunger. The environmental signals come from the body's senses . The feeling of hunger could be triggered by the smell and thought of food, the sight of a plate, or hearing someone talk about food. The signals from the stomach are initiated by the release of the peptide hormone ghrelin . Ghrelin is a hormone that increases appetite by signaling to
7488-464: The hypothalamus that produce hunger, melanin concentrating hormone (MCH) and orexin . MCH plays a bigger role in producing hunger. In mice, MCH stimulates feeding and a mutation causing the overproduction of MCH led to overeating and obesity. Orexin plays a greater role in controlling the relationship between eating and sleeping. Other peptides in the hypothalamus that induce eating are neuropeptide Y (NPY) and agouti-related protein (AGRP). Satiety in
7605-599: The BMI metric. However, their mean body fat percentage , 14%, is well within what is considered a healthy range. Similarly, Sumo wrestlers may be categorized by BMI as "severely obese" or "very severely obese" but many Sumo wrestlers are not categorized as obese when body fat percentage is used instead (having <25% body fat). Some Sumo wrestlers were found to have no more body fat than a non-Sumo comparison group, with high BMI values resulting from their high amounts of lean body mass. Canada utilises BMI sparingly within their method of defining levels of obesity through use of
7722-655: The BioSHaRE– EU Healthy Obese Project (sponsored by Maelstrom Research, a team under the Research Institute of the McGill University Health Centre ) came up with two definitions for healthy obesity , one more strict and one less so: To come up with these criteria, BioSHaRE controlled for age and tobacco use, researching how both may effect the metabolic syndrome associated with obesity, but not found to exist in
7839-489: The Edmonton Scale (for adult obesity). This scale also introduces factors such as Quality of Life, Mental Health & Mobility amongst others. In recent years, Canada chose to allow both Chilli & Ireland to adapt their obesity guidelines to suit both countries' health systems. In Ireland, obesity is now defined as "a Complex, Chronic & Relapsing Disease". Therefore it is now viewed as requiring intervention from
7956-494: The UK recommend three meals a day (with between 400 and 600 kcal per meal), with four to six hours between. Having three well-balanced meals (described as: half of the plate with vegetables, 1/4 protein food as meat, [...] and 1/4 carbohydrates as pasta, rice) will then amount to some 1800–2000 kcal, which is the average requirement for a regular person. In jurisdictions under Sharia law , it may be proscribed for Muslim adults during
8073-527: The United States and Europe have led to lower food prices . In the United States, subsidization of corn, soy, wheat, and rice through the U.S. farm bill has made the main sources of processed food cheap compared to fruits and vegetables. Calorie count laws and nutrition facts labels attempt to steer people toward making healthier food choices, including awareness of how much food energy is being consumed. Obese people consistently under-report their food consumption as compared to people of normal weight. This
8190-455: The United States found leisure-time physical activity has not changed significantly. Physical activity in children may not be a significant contributor. In both children and adults, there is an association between television viewing time and the risk of obesity. Increased media exposure increases the rate of childhood obesity, with rates increasing proportionally to time spent watching television. Like many other medical conditions, obesity
8307-894: The United States increased from 14.5% to 30.9%. During the same period, an increase occurred in the average amount of food energy consumed. For women, the average increase was 335 calories (1,400 kJ) per day (1,542 calories (6,450 kJ) in 1971 and 1,877 calories (7,850 kJ) in 2004), while for men the average increase was 168 calories (700 kJ) per day (2,450 calories (10,300 kJ) in 1971 and 2,618 calories (10,950 kJ) in 2004). Most of this extra food energy came from an increase in carbohydrate consumption rather than fat consumption. The primary sources of these extra carbohydrates are sweetened beverages, which now account for almost 25 percent of daily food energy in young adults in America, and potato chips. Consumption of sweetened beverages such as soft drinks, fruit drinks, and iced tea
8424-502: The WHO and CDC , in the USA alone, annually, there are 76 million cases of foodborne illness leading to 325,000 hospitalizations and 5,000 deaths. From 2011 to 2016, on average, there were 668,673 cases of foodborne illness and 21 deaths each year. In addition, during this period, 1,007 food poisoning outbreaks with 30,395 cases of food poisoning were reported. Obesity Obesity
8541-579: The WHO defines obesity as a BMI two standard deviations above the median for their age (a BMI around 18 for a five-year old; around 30 for a 19-year old). For children under five, the WHO defines obesity as a weight three standard deviations above the median for their height. Some modifications to the WHO definitions have been made by particular organizations. The surgical literature breaks down class II and III or only class III obesity into further categories whose exact values are still disputed. As Asian populations develop negative health consequences at
8658-450: The ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns. Attitudes toward body weight held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found among friends, siblings, and spouses. Stress and perceived low social status appear to increase risk of obesity. Smoking has
8775-607: The air or water and are the basic nutrients needed for plant survival. The three main nutrients absorbed from the soil for plant growth are nitrogen, phosphorus and potassium, with other important nutrients including calcium, sulfur, magnesium, iron boron, chlorine, manganese, zinc, copper molybdenum and nickel. Bacteria and other microorganisms also form the lower rungs of the food chain. They obtain their energy from photosynthesis or by breaking down dead organisms, waste or chemical compounds. Some form symbiotic relationships with other organisms to obtain their nutrients. Bacteria provide
8892-533: The amount of snacks they ate between meals was greater. One possible explanation that Lowe and Fisher suggest is obese individuals often eat their meals with others and do not eat more than average due to the reduction of distress because of the presence of other people. Another possible explanation would be that obese individuals do not eat more than the others while having meals due to social desirability. Conversely, snacks are usually eaten alone. There are many physiological mechanisms that control starting and stopping
9009-440: The apex predators, the animals that have no known predators in its ecosystem. Humans are considered apex predators. Humans are omnivores, finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed. Cereal grain is a staple food that provides more food energy worldwide than any other type of crop. Corn (maize) , wheat, and rice account for 87% of all grain production worldwide. Just over half of
9126-471: The association of BMI and waist circumference with mortality is U- or J-shaped, while the association between waist-to-hip ratio and waist-to-height ratio with mortality is more positive. In Asians the risk of negative health effects begins to increase between 22 and 25 kg/m . In 2021, the World Health Organization estimated that obesity caused at least 2.8 million deaths annually. On average, obesity reduces life expectancy by six to seven years,
9243-490: The benefits towards "healthier living" having physical benefits without dynamic shifts on the scales. Plus living with stigma surrounding the shape of one's body or actual treatments for the disease of obesity, be they medicinal or surgical, has been shown to greatly exacerbate the issue. Obesity increases a person's risk of developing various metabolic diseases, cardiovascular disease , osteoarthritis , Alzheimer disease , depression , and certain types of cancer. Depending on
9360-446: The body's response to insulin, potentially leading to insulin resistance . Increased fat also creates a proinflammatory state , and a prothrombotic state. Newer research has focused on methods of identifying healthier obese people by clinicians, and not treating obese people as a monolithic group. Obese people who do not experience medical complications from their obesity are sometimes called (metabolically) healthy obese , but
9477-423: The body. The brain stem's involvement of food intake has been researched using rats. Rats that have had the motor neurons in the brain stem disconnected from the neural circuits of the cerebral hemispheres (decerebration), are unable to approach and eat food. Instead, they must obtain their food in a liquid form. This research shows that the brain stem does in fact play a role in eating. There are two peptides in
9594-404: The brain that a person is hungry. Environmental signals and ghrelin are not the only signals that initiate hunger, there are other metabolic signals as well. As time passes between meals, the body starts to take nutrients from long-term reservoirs. When the glucose levels of cells drop (glucoprivation), the body starts to produce the feeling of hunger. The body also stimulates eating by detecting
9711-802: The case of hyenas , allowing them to consume bones; some extinct groups, notably the Machairodontinae , had saber-shaped canines . Some physiological carnivores consume plant matter and some physiological herbivores consume meat. From a behavioral aspect, this would make them omnivores, but from the physiological standpoint, this may be due to zoopharmacognosy . Physiologically, animals must be able to obtain both energy and nutrients from plant and animal materials to be considered omnivorous. Thus, such animals are still able to be classified as carnivores and herbivores when they are just obtaining nutrients from materials originating from sources that do not seemingly complement their classification. For example, it
9828-442: The daylight hours of Ramadan . Newborn babies do not eat adult foods. They survive solely on breast milk or formula . Small amounts of pureed food are sometimes fed to young infants as young as two or three months old, but most infants do not eat adult food until they are between six and eight months old. Young babies eat pureed baby foods because they have few teeth and immature digestive systems. Between 8 and 12 months of age,
9945-587: The degree of obesity and the presence of comorbid disorders, obesity is associated with an estimated 2–20 year shorter life expectancy. High BMI is a marker of risk for, but not a direct cause of, diseases caused by diet and physical activity. Obesity is one of the leading preventable causes of death worldwide. The mortality risk is lowest at a BMI of 20–25 kg/m in non-smokers and at 24–27 kg/m in current smokers, with risk increasing along with changes in either direction. This appears to apply in at least four continents. Other research suggests that
10062-534: The different regions of the world, as culture influences the way people eat their meals. For example, most of the Middle Eastern countries, eating while sitting on the floor is most common, and it is believed to be healthier than eating while sitting at a table. Eating in a reclining position was favored by the Ancient Greeks at a celebration they called a symposium , and this custom was adopted by
10179-525: The digestive system improves, and many babies begin eating finger foods. Their diet is still limited, however, because most babies lack molars or canines at this age, and often have a limited number of incisors . By 18 months, babies often have enough teeth and a sufficiently mature digestive system to eat the same foods as adults. Learning to eat is a messy process for children, and children often do not master neatness or eating etiquette until they are five or six years old. Eating positions vary according to
10296-517: The dramatic increase seen within specific countries or globally. Though it is accepted that energy consumption in excess of energy expenditure leads to increases in body weight on an individual basis, the cause of the shifts in these two factors on the societal scale is much debated. There are a number of theories as to the cause but most believe it is a combination of various factors. The correlation between social class and BMI varies globally. Research in 1989 found that in developed countries women of
10413-517: The drive to eat. Dietary energy supply per capita varies markedly between different regions and countries. It has also changed significantly over time. From the early 1970s to the late 1990s the average food energy available per person per day (the amount of food bought) increased in all parts of the world except Eastern Europe. The United States had the highest availability with 3,654 calories (15,290 kJ) per person in 1996. This increased further in 2003 to 3,754 calories (15,710 kJ). During
10530-525: The entire body. In anorexia nervosa, people restrict their calorie intake out of fear of gaining weight. This malnutrition leads to an unhealthy weight, significantly impacting overall health. Bulimia is characterized by recurrent episodes of binge eating, involving the consumption of a substantial amount of food within a short period. Subsequently, individuals engage in maladaptive behaviors, such as inducing vomiting, excessive physical activity, and using laxatives as compensatory measures. If eating and drinking
10647-482: The environment, increased phenotypic variance via assortative mating , social pressure to diet , among others. According to one study, factors like these may play as big of a role as excessive food energy intake and a lack of physical activity; however, the relative magnitudes of the effects of any proposed cause of obesity is varied and uncertain, as there is a general need for randomized controlled trials on humans before definitive statement can be made. According to
10764-567: The essential amino acids that the human body needs. One 4-ounce (110 g) steak, chicken breast or pork chop contains about 30 grams of protein. One large egg has 7 grams of protein. A 4-ounce (110 g) serving of cheese has about 15 grams of protein. And 1 cup of milk has about 8 grams of protein. Other nutrients found in animal products include calories, fat, essential vitamins (including B12) and minerals (including zinc, iron, calcium, magnesium). Food products produced by animals include milk produced by mammary glands , which in many cultures
10881-493: The existence of metabolically healthy obesity—the metabolically healthy obese are often found to have low amounts of ectopic fat (fat stored in tissues other than adipose tissue) despite having overall fat mass equivalent in weight to obese people with metabolic syndrome . Although the negative health consequences of obesity in the general population are well supported by the available research evidence, health outcomes in certain subgroups seem to be improved at an increased BMI,
10998-667: The extent to which this group exists (especially among older people) is in dispute. The number of people considered metabolically healthy depends on the definition used, and there is no universally accepted definition. There are numerous obese people who have relatively few metabolic abnormalities, and a minority of obese people have no medical complications. The guidelines of the American Association of Clinical Endocrinologists call for physicians to use risk stratification with obese patients when considering how to assess their risk of developing type 2 diabetes. In 2014,
11115-471: The fact that people often lose weight as they become progressively more ill. Similar findings have been made in other types of heart disease. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, the risk of further cardiovascular events is increased. Even after cardiac bypass surgery , no increase in mortality
11232-409: The fat stored in adipose tissue. Adipose tissue secretes the hormone leptin , and leptin suppresses appetite. Long-term satiety signals from adipose tissue regulates short-term satiety signals. Cessation of eating within two hours of sleeping can reduce body weight. The brain stem can control food intake, because it contains neural circuits that detect hunger and satiety signals from other parts of
11349-447: The food and agricultural systems are one of the major contributors to climate change , accounting for as much as 37% of total greenhouse gas emissions . The food system has significant impacts on a wide range of other social and political issues, including sustainability , biological diversity , economics , population growth , water supply , and food security . Food safety and security are monitored by international agencies like
11466-550: The form of starch, fructose, glucose and other sugars. Most vitamins are found from plant sources, with exceptions of vitamin D and vitamin B 12 . Minerals can also be plentiful or not. Fruit can consist of up to 90% water, contain high levels of simple sugars that contribute to their sweet taste, and have a high vitamin C content. Compared to fleshy fruit (excepting Bananas) vegetables are high in starch, potassium , dietary fiber, folate and vitamins and low in fat and calories. Grains are more starch based and nuts have
11583-1075: The hypothalamus is stimulated by leptin. Leptin targets the receptors on the arcuate nucleus and suppresses the secretion of MCH and orexin. The arcuate nucleus also contains two more peptides that suppress hunger. The first one is cocaine- and amphetamine-regulated transcript (CART), the second is α-MSH (α- melanocyte-stimulating hormone ). Physiologically, eating is generally triggered by hunger , but there are numerous physical and psychological conditions that can affect appetite and disrupt normal eating patterns. These include depression , food allergies , ingestion of certain chemicals, bulimia , anorexia nervosa , pituitary gland malfunction and other endocrine problems, and numerous other illnesses and eating disorders . A chronic lack of nutritious food can cause various illnesses, and will eventually lead to starvation . While changes in appetite can result from various physical and psychological conditions, including depression, allergies, and anxiety; anorexia and bulimia are specific eating disorders that profoundly impact
11700-467: The intestines, as additional energy during migration. Birds that employ many strategies to obtain food or feed on a variety of food items are called generalists, while others that concentrate time and effort on specific food items or have a single strategy to obtain food are considered specialists. Avian foraging strategies can vary widely by species. Many birds glean for insects, invertebrates, fruit, or seeds. Some hunt insects by suddenly attacking from
11817-485: The late 1990s, Europeans had 3,394 calories (14,200 kJ) per person, in the developing areas of Asia there were 2,648 calories (11,080 kJ) per person, and in sub-Saharan Africa people had 2,176 calories (9,100 kJ) per person. Total food energy consumption has been found to be related to obesity. The widespread availability of dietary guidelines has done little to address the problems of overeating and poor dietary choice. From 1971 to 2000, obesity rates in
11934-408: The liver. The long-term signals of satiety come from adipose tissue . The taste and odor of food can contribute to short-term satiety, allowing the body to learn when to stop eating. The stomach contains receptors to allow us to know when we are full. The intestines also contain receptors that send satiety signals to the brain. The hormone cholecystokinin is secreted by the duodenum , and it controls
12051-448: The main treatments recommended by health professionals. Diet quality can be improved by reducing the consumption of energy-dense foods, such as those high in fat or sugars, and by increasing the intake of dietary fiber , if these dietary choices are available, affordable, and accessible. Medications can be used, along with a suitable diet, to reduce appetite or decrease fat absorption. If diet, exercise, and medication are not effective,
12168-413: The metabolically healthy obese. Other definitions of metabolically healthy obesity exist, including ones based on waist circumference rather than BMI, which is unreliable in certain individuals. Another identification metric for health in obese people is calf strength , which is positively correlated with physical fitness in obese people. Body composition in general is hypothesized to help explain
12285-614: The needs of their metabolisms and have evolved to fill a specific ecological niche within specific geographical contexts. Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. Humans generally use cooking to prepare food for consumption. The majority of the food energy required is supplied by the industrial food industry , which produces food through intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels , which means that
12402-595: The other. Since plants and meat are digested differently, there is a preference for one over the other, as in bears where some species may be mostly carnivorous and others mostly herbivorous. They are grouped into three categories: mesocarnivory (50–70% meat), hypercarnivory (70% and greater of meat), and hypocarnivory (50% or less of meat). The dentition of hypocarnivores consists of dull, triangular carnassial teeth meant for grinding food. Hypercarnivores, however, have conical teeth and sharp carnassials meant for slashing, and in some cases strong jaws for bone-crushing, as in
12519-413: The plant that can be eaten, including roots, stems, leaves, flowers, bark or the entire plant itself. These include root vegetables (potatoes and carrots), bulbs (onion family), flowers (cauliflower and broccoli), leaf vegetables ( spinach and lettuce) and stem vegetables (celery and asparagus ). The carbohydrate, protein and lipid content of plants is highly variable. Carbohydrates are mainly in
12636-435: The rate at which the stomach is emptied. This hormone is thought to be a satiety signal to the brain. Peptide YY 3-36 is a hormone released by the small intestine and it is also used as a satiety signal to the brain. Insulin also serves as a satiety signal to the brain. The brain detects insulin in the blood, which indicates that nutrients are being absorbed by cells and a person is getting full. Long-term satiety comes from
12753-428: The reasons behind it are myriad, however, its prevalence has led some to declare an " obesity epidemic ". Many homes have a large kitchen area devoted to preparation of meals and food, and may have a dining room, dining hall, or another designated area for eating. Most societies also have restaurants , food courts , and food vendors so that people may eat when away from home, when lacking time to prepare food, or as
12870-405: The separation of ecological niches . Loons , diving ducks , penguins and auks pursue their prey underwater, using their wings or feet for propulsion, while aerial predators such as sulids , kingfishers and terns plunge dive after their prey. Flamingos , three species of prion , and some ducks are filter feeders . Geese and dabbling ducks are primarily grazers. Food Food
12987-692: The slow, complex digestive process of an herbivore. Larger animals, on the other hand, generate more heat and less of this heat is lost. They can therefore tolerate either a slower collection process (carnivores that feed on larger vertebrates) or a slower digestive process (herbivores). Furthermore, mammals that weigh more than 18 ounces (510 g; 1.1 lb) usually cannot collect enough insects during their waking hours to sustain themselves. The only large insectivorous mammals are those that feed on huge colonies of insects ( ants or termites ). Some mammals are omnivores and display varying degrees of carnivory and herbivory, generally leaning in favor of one more than
13104-493: The strongest is the link with type 2 diabetes . Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women. Health consequences fall into two broad categories: those attributable to the effects of increased fat mass (such as osteoarthritis , obstructive sleep apnea , social stigmatization) and those due to the increased number of fat cells ( diabetes , cancer , cardiovascular disease , non-alcoholic fatty liver disease ). Increases in body fat alter
13221-448: The tastes that provide the most energy are the most pleasant to eat while others are not enjoyable, although humans in particular can acquire a preference for some substances which are initially unenjoyable. Water, while important for survival, has no taste. Sweetness is almost always caused by a type of simple sugar such as glucose or fructose , or disaccharides such as sucrose , a molecule combining glucose and fructose. Sourness
13338-523: The top. Other aspects of the web include detrovores (that eat detritis ) and decomposers (that break down dead organisms). Primary producers include algae, plants, bacteria and protists that acquire their energy from sunlight. Primary consumers are the herbivores that consume the plants, and secondary consumers are the carnivores that consume those herbivores. Some organisms, including most mammals and birds, diet consists of both animals and plants, and they are considered omnivores. The chain ends with
13455-536: The way of specialized digestion. Exceptions to this include baleen whales who also house gut flora in a multi-chambered stomach, like terrestrial herbivores. The size of an animal is also a factor in determining diet type ( Allen's rule ). Since small mammals have a high ratio of heat-losing surface area to heat-generating volume, they tend to have high energy requirements and a high metabolic rate . Mammals that weigh less than about 18 ounces (510 g; 1.1 lb) are mostly insectivorous because they cannot tolerate
13572-403: The world's crops are used to feed humans (55 percent), with 36 percent grown as animal feed and 9 percent for biofuels . Fungi and bacteria are also used in the preparation of fermented foods like bread , wine , cheese and yogurt . During photosynthesis , energy from the sun is absorbed and used to transform water and carbon dioxide in the air or soil into oxygen and glucose. The oxygen
13689-501: Was consistently found that obese individuals experience negative emotions more frequently and more intensively than do normal weight persons. The naturalistic study by Lowe and Fisher compared the emotional reactivity and emotional eating of normal and overweight female college students. The study confirmed the tendency of obese individuals to overeat, but these findings applied only to snacks, not to meals. That means that obese individuals did not tend to eat more while having meals; rather,
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