A lot of it is about the evidence for a genetic basis for what people weigh--a study of children adopted at between one month and one year found that the kids' weights tracked their biological parents weights, not their adopted parents' weights.
There's plenty about efforts at weight loss making people miserable, and the beliefs that lead to trying one diet after another.
An interesting thing about Atkins: It was popular in the 70s, and when it came back more recently, no one seemed to ask whether the people who tried it back then were able to stay on it. Mostly they didn't.
There also isn't evidence that being fat is strikingly bad for your health. Being unusually light or heavy carries some risk, but being overweight implies more longevity than being at a "normal" weight. Kolata suggests that rather than a "fat epidemic", the human race is metamorphosing into a variant which is taller, fatter, and longer-lived.
There's a fair amount about the hormones and genes associated with hunger and satiety, but apparently the subject gets more complex the more it's studied. Some of this knowledge took animal experiments which almost make me want to join PETA.
Fat people who are dieting are metabolically and psychologically a lot like starving thin people.
Fat people aren't more neurotic than thin people, and eating for comfort or out of habit appears at all weight levels.
A very few people have genetic damage which makes them ravenously hungry *all* the time. Sometimes hormone therapy solves the problem completely.
Read the book. It's only 220 pages, and this is major stuff.