Someone really needs to do something about companies like weight watchers. And our idea of fat people needs to change. Fat is not ugly or lazy or even unhealthy in many cases. And dieting does not work.

There is a reason that fat people cannot stay thin after they diet and that thin people cannot stay fat when they force themselves to gain weight. The body’s metabolism speeds up or slows down to keep weight within a narrow range. Gain weight and the metabolism can as much as double; lose weight and it can slow to half its original speed.

In fact, it can be pretty unhealthy:

fat people who lost large amounts of weight might look like someone who was never fat, but they were very different. In fact, by every metabolic measurement, they seemed like people who were starving.

And not just physical health is affected:

The Rockefeller subjects also had a psychiatric syndrome, called semi-starvation neurosis, which had been noticed before in people of normal weight who had been starved. They dreamed of food, they fantasized about food or about breaking their diet. They were anxious and depressed; some had thoughts of suicide. They secreted food in their rooms. And they binged.

It turns out that weight is inherited genetically. And it’s more strongly inherited than almost any other condition. Your body works hard to maintain that weight by controlling metabolism and appetite. Telling a fat person to diet, that all you have to do is eat less and exercise more, is wrong.

“Those who doubt the power of basic drives, however, might note that although one can hold one’s breath, this conscious act is soon overcome by the compulsion to breathe,” Dr. Friedman wrote. “The feeling of hunger is intense and, if not as potent as the drive to breathe, is probably no less powerful than the drive to drink when one is thirsty. This is the feeling the obese must resist after they have lost a significant amount of weight.”