Its because people treat it as a DIET and not THE NEW NORMAL.

When you stop a diet, you go back to eating shit. The new normal just keeps you at the same place because you get used to the fact that you don't need to eat breakfast, and a 500 calorie lunch is perfectly satiating, hell maybe a bit too much.

I wonder how much of that is due to a sedentary lifestyle? If you're running and biking and strength training it makes a big difference vs trying to maintain a healthy weight with a low TDEE.