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Research Project Think about the beliefs people have about obe- sity, such as that people who are obese are lazy and don’t exercise. Write down all of the causes of obesity that you know of. This chapter has

given you a couple, such as genetics. Now go to the library and find other causes for obesity. Do some of the results surprise you? Write down all of the causes of obesity that you were unaware of.

Studies have shown that an amino acid, tryptophan, increases in the blood when a person eats carbohydrates. Carbohydrates also stimulate the secretion of insulin, which speeds the uptake of tryptophan into the central nervous system. The tryptophan is then converted to serotonin in the brain. Based on the fact that many depressed and obese people have low serotonin levels and carbohydrates can stimulate serotonin production, many researchers now believe that obese and depressed people are in a sense using food as a medication. The body recognizes serotonin deficiency and triggers the desire for serotonin-friendly foods, specifically carbohydrates. A cycle of feeling blue, craving carbs, eating carbs, feeling better, then feeling blue again sets in. The cycle repeats, and leads to weight gain. Most overweight people crave (and overeat) carbs more than people of “normal” weight. In fact, researchers estimate that as many as two-thirds of those with BMIs over twenty-five are carbohydrate-cravers. Abnormally low serotonin levels could, in effect, be causing their overweight and obesity. Uncontrollable weight gain might just come down to brain chemistry. Self-consciousness, isolation, rejection, low self-esteem, distorted body image, self-deprecation, feelings of failure, depression, and even suicide: all can be potential psychological side effects of obesity. Again, not everyone

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