Overeating - Part 2

In the previous article, I discussed the explanation for the failure of high leptin levels to defend against weight gain. If you think about this failure, it makes good evolutionary sense. Your body doesn't want to be lean but it doesn't really mind getting fat. This is because, during our evolution, being fat was never a risk, while being lean was. If anything, getting fat was a benefit which is why our bodies tend to be so good at it. It's only in modern times when people can get and, more importantly, stay fat for extended periods, that being fat is a problem. Ten thousand years from now, perhaps we will evolve defenses against being fat.

Anyhow, if calories are available all the time, it would make little sense for you to get full and/or start burning them off. This is what would happen if you were extremely sensitive to leptin (and does happen in a small percentage of individuals). Thus, high levels of leptin induce resistance to itself, keeping you hungry and eating while the food is available. Leptin can induce resistance to itself in only a few days of overeating. But we're not really talking about raising leptin above normal here; we're talking about reversing or preventing the drop that occurs with dieting. In that situation, many of the above adaptations to dieting will reverse to one degree or another. What degree will depend on how lean you are, how long you diet, and how long you will overeat.