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Think back to your college days, the good old days when life was easy. Stay up all night partying or even studying? No problem. Eat pizza every night and plow through entire bags of potato chips at one sitting. Hey, no sweat. You were a lean, mean, and oh-so-young machine.  
But . . . then stuff happens. You graduate, get a job, get married, have kids, and around the age of thirty-five you're no longer so young and so lean. In fact, you've added a few pounds around the middle. And with each passing year you seem to put on another pound or two. By the time you've hit your mid forties you may find yourself looking in the mirror and wondering, "What happened to the slim, young Adonis?"

What happened is this. Around the age of thirty-five or so your metabolism may start to slow down. Plus, you are likely to lose muscle mass, which slows your metabolism even more. The slower your metabolism, the slower the rate at which your body burns calories. So even if you're eating less than you used to, you'll start gaining weight.

But just because you're not a spring chicken anymore doesn't mean that you have to get fat. In fact, the antidote is pretty simple: exercise and eat less. Lifting weights or otherwise regularly working your muscles will add or at least maintain muscle mass, which will help maintain your metabolism. And the fewer calories you consume in the first place, the fewer you need to burn.

So maybe you can't stay young forever, but you can stay slim.