Obesity is considered a multifactorial disease with a strong genetic component. Acting upon a genetic background is a number of hormonal, metabolic, psychological, cultural, and behavioral factors that promote fat accumulation and weight gain.
Positive Energy Balance
A positive energy balance causes weight gain and occurs when the amount of calories consumed (energy intake) exceeds the number of calories the body uses (energy expenditure) in the performance of basic biological functions, daily activities, and exercise. A positive energy balance may be caused by overeating or by not getting enough physical activity. However, there are other conditions that affect energy balance and fat accumulation that do not involve excessive eating or sedentary behavior. These include:
- Chronic sleep loss
- Consumption of foods that, independent of caloric content, cause metabolic/hormonal changes that may increase body fat. These include foods high in sugar or high fructose corn syrup, processed grains, fat, and processed meats
- Low intake of fat-fighting foods such as fruits, vegetables, legumes, nuts, seeds, quality protein
- Stress and psychological distress)
- Many types of medications
- Various pollutants
Weight gain is yet another contributor to weight gain or, in other words, obesity ‘begets’ obesity, which is one of the reasons the disease is considered ‘progressive’. Weight gain causes a number of hormonal, metabolic, and molecular changes in the body that increase the risk for even greater fat accumulation. Such obesity-associated biological changes reduce the body’s ability to oxidize (burn) fat for energy, increase the conversion of glucose (carbohydrate) to fat, and increase the body’s capacity to store fat in fat storage depots (adipose tissue). This means that more of the calories consumed will be stored as fat. To make matters worse, obesity affects certain regulators of appetite and hunger in a manner that can lead to an increase in meal size and the frequency of eating. Weight gain, therefore, changes the biology of the body in a manner that favors further weight gain and obesity.