Race Against Time
Beat the downshift in metabolism that comes with aging: With each passing decade, a woman's metabolism slows by about 5 percent. Hormones play a role, but mostly it's because as you get older, you typically become less active. As a result, you lose muscle mass, a major consumer of all those calories you scarf down.
So by the time you hit 35, you'll burn 75 fewer calories a day than you did at 25; by age 65 you'll burn 500 fewer, says Madelyn Fernstrom, Ph.D., director of the Weight Management Center at the University of Pittsburgh. You can outsmart Mother Nature with the tips provided. Here's what happens if you don't:
20s: Your muscle and bone mass are at their peak.
30s: Your mitochondria—cellular powerhouses that fuel muscles to use more oxygen and burn more energy—become less effective.
40s: A drop in estrogen production further slows metabolism.
50s: Sharp decreases in activity reduce the levels of hormones responsible for maintaining lean muscle mass and bone density.