Depo-Provera. The birth control shot may be convenient, but it delivers a high dose of progesterone, which can cause appetite to increase. Seventy percent of women who use it gain weight, with nearly half gaining more than five pounds after a year. The solution: Consider lower-dose possibilities. The Pill may get a bad rap for causing weight gain, but in a review published earlier this year researchers found no correlation between oral contraceptives and added pounds. Another low-dose option is the Ortho Evra patch.
Artificial sweeteners. A recent Purdue University study compared two sets of rats: those fed liquid spiked with saccharin, others fed liquid sweetened with natural sugar. When both groups were later given a sugary snack, the rats accustomed to artificial sweeteners ate more. "Our bodies have ways of judging how many calories a food has from how it tastes, and artificial sweeteners may mess up that natural regulating process," says Susan Swithers, PhD, associate professor of psychological sciences at Purdue and one of the study's lead authors. The solution: "We're not suggesting you give up your diet soda at this point," Swithers says. But if you consume artificially sweetened products, pay extra attention to the calorie count of everything you eat, especially snacks with real sugar.
Missing meals. Research shows that people who eat breakfast are less likely to be overweight, and that morning meals seem to help those who've lost weight keep it off. It's not just breakfast, either: Denise Bruner, MD, obesity specialist and former president of the American Society of Bariatric Physicians, says that skipping meals of any kind results in a "tremendous bout of compensatory hunger." The solution: Eat small meals throughout the day. A steady nutrient intake will keep your blood sugar relatively constant, helping prevent out-of-control binges.
Dining out. Super Size Me gave fast food a bad name, but restaurant portions can be just as oversize as a McDonald's meal. An order of chicken Parmesan and pasta at Ruby Tuesday, for example, tops out at 1,466 calories—more than a Big Mac, large fries, and a Coke combined. The solution: Eating out is fine, as long as you don't use it as a frequent license to indulge. Choose your entrees wisely, and find restaurants that serve smaller portions or doggie bag half your meal.