Nutrition is the decisive, central factor in losing weight—there is no doubt about that. However, the project of becoming slim is most likely to succeed when, in addition to changing eating habits, the following are also actively integrated: more physical activity and more relaxation—because these are the supportive yin & yang that should accompany a change in diet. The focus is not on specific sports or relaxation methods; rather, what matters is that both bring joy to life and are fun, and that the intrinsic motivation to “want to do it” is tangible. Maintaining and building muscle plays a central role in this for several important reasons.