Remember those pizza-and-margarita binges you went on in your single-girl-about-town days? Or all the peanut butter and jelly sandwich crusts you inhaled when your kids were picky toddlers? You might have been able to eat that way regularly and still fit into your pants the next morning. Now? Simply eyeing a slice of pepperoni seems to cause instantaneous weight gain, and although your kids don't leave the sandwich crusts any longer, as hungry teens they seem to need an endless supply of calorie-laden snacks. Usually left right out where you can't help but see them and be tempted.

You can sail through your twenties and thirties with a washboard stomach, but once you hit the big 4-0, you'll probably find a bit-or a lot-of pooch creeping up on you. The culprit? Declining estrogen levels. During your prime childbearing years, your body is programmed to store fat in the hips and thighs to provide a calorie cushion for breastfeeding. This fat contains estrogen receptors. But when levels of the hormone start to decrease, as they do in perimenopause, the receptors are no longer activated. The result is that your body begins to store fat elsewhere-namely, in your stomach. That flat tummy you were so proud of for so long is no longer.

While it's necessary to cut calories overall as you age in order to avoid weight gain, what you eat is just as important as what you don't. Especially important at this age? Calcium, for one. Since bone-building estrogen levels are declining at this age, and you absorb less of the calcium you ingest due to changes in your stomach acid, you need to get more of this mineral. Go for 1,000 milligrams a day by eating yogurt, low-fat cheeses, skim milk, or fortified orange juice. Take a supplement if you're still not meeting this amount.

Another crucial nutrient is Vitamin D, which helps your body absorb calcium, protects against certain cancers, and keeps your immune system humming. There are very few foods that contain it, however, so it's best to take a supplement. You can find Vitamin D in fortified milk and orange juice, and small amounts of sunlight will give you an extra boost.

Finally, fiber is very important for your gastrointestinal system. It keeps bloating to a minimum and helps you stay satisfied longer after eating. It also knocks down your cholesterol level and decreases your risk of colon cancer. Your best bet? A mix of fruits, veggies, oats, and whole-grain breads and other healthful carbs.