You eat the same, you exercise the same, but that pooch around your middle was never there before.
What's going on?
If you're a woman over 40, there's good news and bad news. The bad news is, as your hormones drop off as you get older, you lose muscle mass and your metabolism slows down. That means that sandwich you ate and forgot about when you were 20 is more likely to be stored on your haunches as fat now that you're, well, not 20 anymore.
He said most notably, the decrease in thyroid as a woman ages slows her ability to burn calories, and that means you can't eat as much as you used to.
So why isn't every woman in her 50s taking a thyroid supplement? Barr said that leads to bone loss and is a difficult hormone to balance.
The good news is, you can rev your metabolism back up with exercise.
But, Barr said not all exercise is created equal. When you were in your 20s, you could go running and burn a bunch of calories and feel pretty good about whatever you ate.
Now that you're older, you can't keep up that way. As Barr put it: "How much time can you really spend running?"
A better plan, he said, is to slow down and pick up some weights to replace the muscle mass that you've lost with age.
Trainer Robin Hart, owner of At One Fitness in North Hollywood, said that creates a "forever change." Instead of burning calories for an hour or two while you're out for a run, she said you're changing your body to burn fat for you.
Hart said every pound of muscle on your body burns 55 calories a day, while fat burns 6 calories per day, per pound, so "the more muscle you have, the more calories you're burning, even when you sleep."
At One Fitness