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Causes of Obesity


There are many possible reasons for a person's body shape.
Increasing numbers of people (including children) are affected by obesity, especially in relatively rich parts of the world. This is a major health concern due to the many health risks of obesity.

The various causes of obesity include issues that an obese person is more, and less, likely to be able to do something about e.g. choices of food and exercise can be adjusted while the effects of hormone problems, medication/drugs and genetics may be more challenging, if in any way possible to change at all.

List of 10 Causes of Obesity:

  1. Energy intake vs energy usage - The body needs a certain amount of energy (from food) to support and renew its tissues and structures and to perform daily tasks. The required energy varies with age, gender, lifestyle, and sometimes individual medical issues / biochemistry e.g. in cases of hormone imbalances. Ingestion of more energy (in foods) than is used by the body generally results in the excess "energy" from the food accumulating as fat in the body. If this happens to a significant extent and builds-up over time, the person's risk of obesity increases considerably.

  2. Types of foods eaten - Some types of foods contain more energy (higher calories) than other types of foods. Some foods can be more efficiently broken-down and used by the body than other foods. Therefore the types of foods consumed - as well as the amounts (see below) - affect the liklihood of the person putting on excessive weight, potentially resulting in obesity.

  3. Eating habits - The types of foods eaten is just one aspect of eating habits. The habit of eating regular meals, including eating breakfast, is associated with lower risk of obesity whereas a less structured lifestyle that includes frequently eating unhealthy snacks while also pursuing other tasks is associated with higher risk of obesity. Another important eating habit associated with increased risk of obesity is large portion sizes. Even when healthy foods are selected, the amount consumed is a very important consideration: Eating too much can lead to obesity.

  4. Metabolic factors - The efficiency with which food energy is converted into energy for use by a person's body (any excess being stored as fat) varies from person to person. Metabolic rate depends several factors including basal metabolic rate (BMR), which is metabolic rate at rest, and physical activity level. The hormone thyroxin (which is secreted by the thyroid gland in the neck) is important for regulation of BMR. Insufficient production and release of this hormone can increase the risk of obesity - see (8. Hormonal Factors) and may therefore be a cause of obesity.

  5. Physical Activity Level (PAL) - The amount of time a person is physically active and the type of exercise that he or she takes affects the amount of energy he or she uses. Put another way, physical activity affects metabolic rate, which determines the amount of energy a person needs to consume in food - hence the amount of food energy intake beyond which he or she is likely to store excess food energy as fat. Low levels of physical activity are associated with higher risk of obesity: Not taking enough exercise may therefore be included as one of the causes of obesity.
  1. Psychological Factors - Stress can affect body mass. Depending on a person's biochemical and psychological responses to emotions such as stress, anxiety, depression and self-worth he or she may lose weight during periods of intense emotion - either due to his or her metabolic responses and/or, in some cases, due to a tendency to eat less under those circumstances. Alternatively, in the same situation other people may respond by eating and/or drinking more, and/or consuming more of the types of foods and drinks that are most likely to result in weight gain, potentially leading to obesity. In some cases, extreme eating can be a form of stress-induced behaviour engaged in for emotional reasons rather than due to nutritional need for the food. The initial stress may be due to a wide variety of causes such as bullying at school or at work, relationship break-down, bereavement or business/financial problems.

  2. Environmental Factors - The circumstances in which someone grew up, including the food he or she was given and the habits and attitudes that he or she observed and was influenced by can all combine to affect that person's own habits, attitudes and beliefs throughout life. This can affect the person's weight among many other aspects of his or her life., incl. e.g. educational attainment, income, relationships, and so on.

  3. Hormonal Factors - Hormones secreted by the endocrine glands in the body can also affect risk of obesity, especially via their impact on metabolism and metabolic rate. As mentioned above (in 4. Metabolic Factors), the hormone thyroxin (secreted by the thyroid gland) is important for regulation of BMR. Insufficient production and release of thyroxin can result in a condition called hypo-thyroidism whose symptoms include decrease in BMR, weight gain and lethargy (among others). The body's energy and other nutritional requirements also change during pregnancy - whose processes are controlled by other hormones. Hormone problems are therefore one of the medically-related causes of obesity in some people.

  4. Medication - Use of certain types of drugs such as some steroids, antipsychotics, antidepressants, seizure medications and even some medications for diabetes have been associated with weight gain. Any known potential side-effects of drugs are recorded and information is generally available from the practitioner who prescribed the drug and/or the packaging and advice leaflet supplied with it.

  5. Genetic Factors - Correlation between the body mass index (BMI) of parents and their children may be explained in terms of both environmental factors, i.e. children learn lifestyle habits from their parents (as mentioned in 7., above) and genetics. It has been suggested that there is a genetic contribution to some people's chances of becoming obese. However, even in cases in which this applies, obesity is not an inevitable consequence because healthy food and lifestyle choices can make a huge difference.

See also what is a balanced diet? some possible effects of overnutrition and the health risks of obesity.

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