What causes obesity?
Genetic, environmental, psychological, and other factors may all play a role in the development of obesity. Obesity tends to run in families, suggesting a genetic cause. But genes do not destine people to a lifetime of obesity. Although you cannot change your genetic makeup, you can change your eating habits and levels of activity.
Environmental factors strongly influence obesity. This includes lifestyle behaviors such as what you eat and your level of physical activity. Most Americans do not get enough physical activity. Many also tend to eat high-fat foods, and put taste and convenience ahead of nutrition. Psychological factors may also influence eating habits. Many people eat in response to negative emotions such as boredom, sadness, or anger. Up to 10 percent of people who are mildly obese -- and even more who are severly obese -- have binge eating disorder. Those with the most severe binge eating problems are also likely to have symptoms of depression and low self-esteem.
Some illnesses also can lead to obesity, including hypothyroidism, Cushing's syndrome, depression, and certain neurological problems that can lead to overeating. Also, drugs such as steroids and some antidepressants may cause weight gain.
Although there is no definitive explanation for the recent epidemic of obesity, the evolutionary hypothesis comes closest to providing some understanding of this phenomenon. In times when food was scarce, the ability to take advantage of rare periods of abundance and use such abundance by storing energy efficiently was undoubtedly an evolutionary advantage. This is precisely the opposite of what is required in a sedentary society, where high-energy food is available in abundant quantities in the context of decreased exercise. Although many people may have a genetic propensity towards obesity, it is only with the reduction in physical activity and a move towards high-calorie diets of modern society that it has become widespread. Significant proportions (up to 30%) of the population in wealthy countries are now obese, and seen to be at risk of ill health (see e.g. Dr Joel Fuhrman.)
Eating disorders can lead to obesity, especially binge eating disorder (BED). As the name indicates, patients with this disorder are prone to overeat, often in binges. A proposed mechanism is that the eating serves to reduce anxiety, and some parallels with substance abuse can be drawn. An important additional factor is that BED patients often lack the ability to recognize hunger and satisfaction, something that is normally learnt in childhood. Learning theory suggests that early childhood conceptions may lead to an association between food and a calm mental state.
More information on obesity
What is obesity? - Obesity is a condition in which the natural energy reserve of a mammal. In humans, the current measurement of obesity is the body mass index (BMI).
What is morbid obesity? - Morbid obesity is clinically severe obesity or extreme obesity.
What is central obesity? - Central obesity (or 'apple-shaped' or 'masculine' obesity), is when the main deposits of body fat are localised around the abdomen and the upper body.
What is the body mass index (BMI)? - The body mass index (BMI) is a mathematical formula that uses your weight and height information to calculate your body mass.
What causes obesity? - Genetic, environmental, psychological, and other factors may all play a role in the development of obesity.
What're health risks associated with obesity? - Obesity has been linked to several serious medical conditions including: insulin resistance, heart disease and stroke, high blood pressure, type 2 (adult-onset) diabetes, cancer, gallbladder disease and gallstones.
How obesity is measured? - A number of tools are available to measure obesity. Most are based on height and weight ratios, body size and shape, and percent body fat.
How common is obesity? - Most health professionals say that obesity is an epidemic. Obesity in the adult population has doubled since 1980.
What's the treatment of obesity? - The mainstay of treatment for obesity is an energy-limited diet and increased exercise.
What's the dietary therapy for treatment of obesity? - Dietary therapy involves instruction on how to adjust a diet to reduce the number of calories eaten. Reducing calories moderately is essential to achieve a slow but steady weight loss, which is also important for maintenance of weight loss.
What's the exercise therapy (physical activity) for obesity treatment? - The primary goal of this therapy is to move sedentary people into an active category (even if it is moderate levels of intensity) and to move moderate level individuals into more vigorous levels.
What's the behavior therapy (physical activity) for obesity treatment? - Behavior therapy involves changing diet and physical activity patterns and habits to new behaviors that promote weight loss.
What about the drug therapy for obesity treatment? - Drug therapy may be used for weight loss and weight maintenance. Patients should be regularly assessed to determine the effect and continuing safety of a drug.
What about obesity surgery? - Obesity surgery is used to modify the stomach and or intestines to reduce the amount of food that can be eaten.
What's childhood obesity? - Obesity in children and adolescents is a serious issue with many health and social consequences that often continue into adulthood.