All of obesity is genetic or epigenetic. Lifestyle can only cause mild overweight. The reason is as follows: Identical twins have a very high correlation in body weight even when they are reared apart from birth (1). When 12 pairs of identical twins were force fed for 100 days in Canada, there was a range of weight gain but the twins tracked together (2). Individuals that were adopted soon after birth have a statistically significant correlation with the biological parents whom they had never met, but no correlation with the body weight of parents that adopted them(3). At the moment there are 3 known mechanisms for epigenetic obesity. The first, and possibly the most important, occurs before the baby is conceived (4), the second occurs in utero (5) and the third occurs in early life(6). Individuals not carrying a gene for obesity cannot develop obesity because humans have 2 negative feedback systems to prevent it. The first is the hormone leptin, a powerful inhibitor of hunger. It is made mostly in fat cells. There is also a backup negative mechanism that uses Osteocytes in bones to send a message to the brain to eat less (7). The last line of evidence that obesity is genetic is the fact that the body defends weight vigorously by making the individual hungrier and more fuel efficient after modest weight loss (8) in order to go back to the person’s original weight. The body would not do that if obesity was caused simply by poor lifestyle. It is very important that organizations like ANZOS accept this fact because individuals with obesity are discriminated by all of society who believe that obesity is self-induced. By stressing to all of the media and to all politicians that obesity is not self-induced, we can make a start to eliminate bias towards these unfortunate individuals.