Simply stated, it is very rare that a diet actually does what it says it will do. In fact, 95% of all diets fail. This isn't because those who diet don't have will power. It's because our bodies aren't made for deprivation.
Eating in moderation is a different story. But when we restrict our diets so much that we are consistently hungry, the effect is for us to respond strongly to our cravings when we finally allow ourselves to eat. In the long term, this often means gaining back more weight than you lost.
Some then take extreme measures to achieve weight loss or avoid weight gain--sometimes in the form of an eating disorder.
