CAUSES OF OBESITY
When food energy intake exceeds energy expenditure, fat cells (and to a lesser extent muscle and liver cells) throughout the body take in the energy and store it as fat. This is what causes fat deposition around various areas of the body especially the thighs, waist and hips.
So what causes one to eat excessively and not expend those extra calories?
- Psychological –decreased sensitivity to internal cues of hunger
- Watching television! - reduces physical activity and lowers basal/resting metabolic rate
- Physiological – brain serotonin levels, diet induced thermo genesis, metabolism of the fat cells, and sensitivity to insulin
- Studies have shown that with eating diets deficient in tryptophan cause an increase in appetite, resulting in binge eating of carbohydrates
Set point theory – each person has a programmed “set point” weight that is controlled by individual fat cells. When the fat cells become smaller, it sends a powerful signal to the brain to eat. The existence of this set point helps to explain why most diets do not work.
One can fight off the impulse to eat for only so long after which it becomes overpowering and the result is rebound overeating, leading to an increase in weight. In addition the set point is now set at a higher level, making it even more difficult to lose weight. This effect has been termed “yo-yo” eating. The key to stop this increase in set point is increasing sensitivity to insulin by exercise, a specially designed diet and certain nutritional supplements.
The following factors that have been suggested to contribute to the development of obesity:
- Sedentary lifestyle
- A high glycemic diet (i.e. a diet that consists of meals that give high postprandial blood sugar)
- Underlying illness (e.g. hypothyroidism, diabetes)
- Genetic predispositions and disorders (e.g. Prader-Willi syndrome)
- Eating disorders (such as binge eating disorder)
- Stressful events
- Certain medications (e.g. atypical antipsychotics)
- Smoking cessation
- Insufficient sleep or going to sleep too late (usually causes abdominal weight gain)