Our bodies haven't changed genetically in a very long time. But we're getting fatter. What changed?
We now have a steadier supply of food than any of our ancestors had for the last three billion years. And the steadiness and regularity of our food supply is unnatural. Our bodies didn't evolve under such opulent conditions.
There is only one thing to do about it: Artificially induce lean times. That is, fast occasionally. Go without food occasionally. Your mother might have always tried to get you to eat regularly, and you often hear how bad it is for you, but when it's done right, going without food is very healthy indeed.
Learn more about it here: Under-Fasting and the Fountain of Youth.