Yoga: Under pressure, women often eat more—especially sugary treats, which help quell the stress hormone cortisol. So take up yoga, meditate regularly, or at least learn to breathe deeply (not graze avidly) when the stress ratchets up.
Core work: Lie on your back with your knees bent and feet flat on the floor. Raise the lower legs until parallel to the floor, knees still bent and arms relaxed at your sides, palms down. Without using your hands to press, pull in your abs and lift your hips (it feels like a rocking motion) a few inches off the ground. Do three sets: first, 12 to 20 reps; second, 12 to 15 reps; third, eight to ten reps. Rest a minute between sets.
It won't take a day. It won't take a week. But with a little (okay, a lot of) tender loving exercise—some might call it tough love—your tummy can defy the rise and fall of nature's timeline and stay winningly tight.