Willpower is not a muscle, it's a well that fill doing what you enjoy, and clear when used. During my diet, my work ethic was at the bottom, and I couldn't force myself to go out meet new people.
Now that I have a healthier weight and stopped dieting hard (I'm still constantly hungry, but now it's my life), I'm a great coworker, I met a lot of people, made life-changing decisions and I have a lot of willpower left to do all the little things right. If I had a drug that helped me control my appetite at the time, i would have taken it.