One of the reasons behavior mod doesn’t work well for weight loss, is that unlike stopping smoking, you can’t stop and eating and never eat again. Living on bars or formula or cookies can make it easy to lose weight for some patients, because food substitutes remove all choice. If you stick to just formula, you can’t screw up, and you will lose weight. The problem is at some time you have to go off formula and return to food, and without a structure that works for you, every ounce you’ve lost is going to pile back on. Food is exceedingly rewarding, and eating sugar feels good. 75% of soft drinks sold are sugared, not sugar-free, because you don’t get the same kick from Diet Coke as you do from Classic. Sugar-free ice cream doesn’t provide the same high as Haagen Dazs. Eating carbohydrates is self reinforcing. It’s hard to find a behavioral substitute that’s more reinforcing than a carbohydrate high.