What is the answer to belly fat?

I don't want it but wonder if it's inevitable after age 50. You can limit your diet, which means you get less nutrients just when you need them the most. A person can exercise only so much in a day without being obsessed and time consumed. I read in a blob yesterday I need to limit fats to 20% of my daily calorie intake for my age, weight and activity level, which is roughly 2008 calories a day, and I am active.This seems impossible to manage! Is it true? Is lean protein the answer and where does a healthy snack of salmon and a 1/2 bottle of wine fit into that equation?! This battle started at 45 and it appears I'm missing something because it was a non-issue for me for decades due to exercise and diet monitoring.