Science solved this problem way before the shake weight.

Understanding some basic concepts in nutrition/wellness, such as macros and micros, calories, how Energy Expenditure (keeping you alive, walks, lifting weights, etc) and Energy Storage (Fat, Muscle, etc) all ties in with your unique genetics, body composition and lifestyle goes a long way.

Quick and dirty trick: be at a low Body Fat Percentage and have abdominal muscles (which we all do ha).