Is to eat!
Seriously. This is something someone neglected to tell me in my early 20's. The best way to keep your metabolism healthy and active is to eat several small meals in a day and to never let yourself feel hungry.
Why do woman feel like starving themselves is ever going to lead to a healthy weight? Eating lots of good, healthy food is working for me. I wish someone had mentioned this to me 10 years ago. They also probably should have mentioned that vodka and Bucsh light is not a food group.
Live and learn.