Admirable.....At age 64 (soon), I have a stomach that is as flat as a board. Consistent exercise and sensible long-term eating habits are the things that have worked for me.....
For my part I am closing in on 54 and am still in good shape. I no longer sport a sharply defined six pack as I have latterly tired of the extra effort required to maintain this affectation but, nevertheless, my abdomen remains svelte and trim.
Adequate exercise and proper diet are required to achieve physical and psychological well being alike.