While I do very much agree with you that a flat belly is "made in the kitchen", and that you can lose belly fat with a proper, well-balanced lifestyle and diet, there are many surgical ways to get that too (sadly, but hey, no judgement). It's also important to mention that when you say "diet", you mean eating healthy and well-balanced, not starve yourself. When you starve yourself, your body will hold on to whatever fat it can store.