Hunger is the most powerful way that your body uses to keep you from changing your weight and shape. Obese people get just as hungry when they lose weight as skinny people.
Still there are some people who can walk through fire and some who can sleep on a bed of nails and some who can lose a lot of weight and keep it off.
In a recent book, Fat; fighting the obesity epidemic (2001 Oxford University Press) Robert Pool has done a lot of human interest background work by interviewing some of the top researchers in obesity and many of their patients and study subjects. He writes, "Successful long term [weight] losers are a monomaniacal lot, completely obsessed with their weight. Bruce Schneider, a clinical researcher now at the Food and Drug Administration, was working in Hirsch's lab in the early 80's when Leibel [at the Rockefeller University] advertised for people who had maintained a weight loss of 100 lbs for at least a year and a half. 'He got six people,' Schneider recalls, 'and all of them were wacked.' One woman had to run 6 miles a day. If she didn't, she got extremely upset. Another constantly fantasized about food. 'You were basically dealing with chronic starvation;' Schneider says." p.84. Pool's book relates many other stories of the trials and tribulations of the subjects of studies we've mentioned. This suffering is very similar to that of the starved conscientious objectors of Ancel Keys. You don't want to be one of those people.
Another interesting book about a different kind of hunger by Jay Schulkin called Sodium hunger: the search for a salty taste (1991 Cambridge University Press), is all about how and why rats and other animals hunger for salt.
Animals who live in the ocean must strive to keep out salt. Once creatures began to live on land they had to learn to get salt. Salt hunger might represent a good model of hunger. Salt hunger is perhaps easier to examine than hunger for food since the literature is not so voluminous and there aren't all those emotional and social presumptions swirling around.
Items about salt hunger:
-Many organs, the brain, kidneys, liver and heart, have a role in salt metabolism.
-Hormones have an important role in salt hunger.
-There are sex differences.
-Taste and pleasure and the brain modulate it.
-There are species differences in salt seeking effort and behavior.
-How far an animal will go to get salt depends mostly on how deficient it is.
-Humans especially like salt. Everybody remembers from ancient history about how they used to use salt for money. The Yanomamo Indians of South America do not have ready access to salt and can be enslaved for tiny salaries of salt.
-Hypertension might be thought of as a disorder in salt metabolism.
-"Salt hunger, as it turns out, is paradigmatic of an innate specific hunger." p. 138
It has long been understood by medical types that the biggest job of all living things is the maintenance of their internal milieus. That means we have to keep our insides in order. We animals must maintain our temperatures, blood volume, iron, calcium and other mineral stores etc... This kind of house-keeping is called homeostasis. What could be more important to a living creature than its energy homeostasis? No wonder that the forces that maintain Calorie supply are so powerful.