Obesity is often caused by eating too much and moving too little. If large amounts of energy are consumed, especially fats and sugars, but the energy is not burned off through exercise and physical activity, much of the excess energy will be stored by the body as fat. There are many reasons why some people find it difficult to lose weight. Obesity is usually the result of hereditary, physiological and environmental factors, combined with diet, physical activity and exercise choices.
Obesity is a complex health problem that results from a combination of causes and individual factors such as behaviour and genetics. Behaviours may include physical activity, inactivity, dietary patterns, medication use and other exposures. Other contributing factors include the food and physical activity environment, education and skills, and food marketing and promotion. We believe that poverty makes people obese and that obesity makes people poor.
It is more difficult to understand exactly why. Overeating and lack of exercise contribute to obesity. But these lifestyle choices can be changed. If many of the calories you eat come from refined foods or foods high in sugar or fat, you are likely to gain weight.
If you don't get much or any exercise, you will find it hard to lose weight or maintain a healthy weight. Diabetes and heart disease are health problems that can result from being overweight. Being overweight can also affect a person's joints, breathing, sleep, mood and energy levels. So being overweight can affect a person's entire quality of life.
However, there is abundant evidence from around the world that obesity is a condition peculiar to poor people in rich countries. Overweight and obesity are different points on a scale from underweight to morbid obesity. In addition, the people you spend time with can influence your weight: you are more likely to develop obesity if you have friends or family members who are obese. The widespread use of hoovers, dishwashers, leaf blowers and a host of other household appliances takes almost all the physical effort out of daily chores and may contribute as one of the causes of obesity.
However, BMI does not directly measure body fat, so some people, such as muscular athletes, may have a BMI in the obese category even though they do not have excess body fat. Genes contribute to the causes of obesity in many ways, affecting appetite, satiety (the feeling of fullness), metabolism, food cravings, body fat distribution and the tendency to use food as a way of coping with stress. People with obesity may eat more calories before they feel full, feel hungry earlier, or eat more because of stress or anxiety. However, most obesity is probably the result of complex interactions between multiple genes and environmental factors that remain poorly understood (multifactorial obesity).
There are variations in fat and muscle that can make perfectly healthy, muscular men and women technically obese. Being overweight or obese increases the risk of several types of cancer, according to the American Cancer Society. The Department of Agriculture's review of the effect of food stamps found that obesity did not increase among children or men, but did increase slightly among women. A cycle develops that leads to increasing obesity, associated with increasing emotional difficulties.
A new article by John Cawley in the NBER Reporter, The Economics of Obesity, raises an interesting question right at the beginning. Some researchers also think that the very act of eating irregularly and on the run may be another cause of obesity. Conversely, people with a strong genetic predisposition to obesity may not be able to lose weight with the usual forms of diet and exercise therapy.