Diets don't work.
More to the point, any diet will work for awhile. The problem is, at some point, after losing a few pounds (or a lot of pounds) the feeling of deprivation that a diet induces in the dieter causes that person to compensate by overeating. This phenomenon is partly psychological and partly physiological, but it is absolutely real.
Nine out of ten people who lose weight on any given diet will gain it all back, and then some, within the first year after the diet ends. That's why every single diet commercial you've ever seen has the words "results not typical" as a disclaimer at the bottom of each and every testimonial.
In other words, for every single dieting success there are nine failures. And yet, each and every day, thousands of hopeful chubby people start a new diet convinced that this time they will be one of the lucky 10% to be transformed forever into, well, what? Into somebody else.
That's messed up.
There's a saying in AA that goes, "The definition of insanity is doing the same thing over and over and expecting different results."
Why do we maintain the insanity of dieting when we know it's a scam?
Because the weight loss industry and the food industry are both big businesses, and we're human. We're surrounded by the twin messages: Eat! and Diet! so we do both.
Americans eat too many calories and exercise too little, then go on crazy diets to offset a toxic lifestyle crammed with commercial values. I don't think we are fat because we're a nation of pigs with no discipline. I think it's because we are an affluent nation with easy access to lots of fattening delicious food, while at the same time, we are hardworking and miserable.