Obesity

The mitochondria, a part of cells that are involved in energy (calorie) utilization, are only inherited from the parents"; which explains the high correlation of a child's weight to that of the biological parents" weight. This mitochondrial inheritance is compelling evidence supporting the genetic factor of obesity.
             Besides mitochondrial influence, examples of genetically determined hormonal abnormalities exist, which contribute to obesity. Glandular problems are examples .
             of genetic hormonal abnormalities that cause obesity. One glandular problem is clinical hypothyroidism, a disorder in which enough thyroid hormone is not produced to control the normal rates of metabolism. Another problem is Cushing's syndrome, where the production of the corticosteroid hormones is abnormal. Due to these glandular problems, i.e. genetic hormonal differences, individuals respond differently in an environment made constant in food intake and physical activity. Some people store more energy as fat in an environment of excess; others lose less fat in an environment of scarcity. The different responses are largely due to genetic variation between individuals and different genetic variation makes people overweight or obese (Fisher 23). .
             In at least one case, scientists have overestimated the genetic factor of obesity. Leptin, a naturally occurring hormone, which controls the appetite, is a very important genetic factor of obesity. When full, fat cells release appetite curbing hormone, leptin. If leptin production is hindered, the fat cells are unable to signal that they are full and weight gain occurs (Shell 100). Though scientists discovered leptin in the 1990s, as of August 2001, only a few individuals have had abnormalities related to leptin. Though this is a counterexample to genetic factors as a reason of obesity, it is not good enough to disprove genetic factors as one cause of obesity, but we cannot overlook because more evidence of genetic factors exist which cause obesity than evidence of genetic factors not causing obesity.