5 Reasons Your Abs Aren't Showing Yet

A common mistake is training the abs in isolation, says Mike Fantigrassi, director of professional services at the National Academy of Sports Medicine. "The abdominal area is small, so just doing ab exercises isn't going to burn many calories," which is necessary to shed the fat hiding those muscles, he explains. A study published in Journal of Strength and Conditioning Research found that when people did only ab exercises for six weeks, it wasn't enough to reduce abdominal subcutaneous fat, the type that covers the muscles. Plus, some of the most popular ab moves, like full sit-ups, target the hip flexors more than the core (and tax your spine, to boot).

The solution: Focus on the whole body. "You'll burn the most calories by doing cardio two or three days a week and moderate- to high-intensity resistance training two or three days a week," says Cris Dobrosielski, a spokesperson for the American Council on Exercise. You can also cut back your ab-centric circuit to two or three moves per workout, adds Fantigrassi. Spending your gym time doing more total-body weighted movements burns more calories, which in turn helps burn more fat.

You know those squishy midsection lumps you can pinch? That's subcutaneous fat, located just beneath the surface of your skin, says Ursula White, PhD, an obesity researcher at the Pennington Biomedical Research Center at Louisiana State University. Another type of fat, called visceral fat, sits deep within the abdominal area, surrounding the organs. This is the kind that's considered especially harmful; research has found that excess amounts of visceral fat may put your at a higher risk of heart disease and type 2 diabetes.

Where we pack on flab may be determined by genetics, says White. But in general, notes Tara Collingwood, RDN, coauthor of Flat Belly Cookbook for Dummies ($23; amazon.com) when people gain weight, it often increases their amount of visceral fat. That's one reason a diet that's too high in simple carbs is so problematic: "Eating too many low-fiber, high-sugar foods can spike levels of insulin, which then stores all those calories as fat," explains Collingwood.

The solution: You can't fight genetics—but you can make it harder for your body to store excess calories as fat by limiting your consumption of refined carbs. Eat more high-fiber foods instead, such as oats, beans, and sweet potatoes, suggests Leslie Bonci, RDN, owner of Active Eating Advice. Also, aim to eat three meals and one snack a day—and have them on a set schedule, recommends Bonci. One 2014 study found that eating erratically was linked to a bigger waist circumference than sticking to a schedule.

Being planted in a chair all day does cause your metabolism to slow down, a number of studies have shown (One hour of sitting burns only 93 calories, whereas walking at a moderate pace for an hour burns 200.) And a new study published in International Journal of Obesity found that people with a desk job tend to have thicker waists and a higher risk of heart disease than those who are more mobile during the workday.

Posture plays a role, too: Sitting shortens your hip flexors and psoas, the muscles deep within your abdominal cavity that attach to the bones of your lower back. This in turn tilts your hips forward and pushes your belly out, says Ashley Borden, a celebrity fitness trainer who has worked with Reese Witherspoon, Many Moore, and Ryan Gosling.

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The solution: Start walking, standing, pacing, and fidgeting throughout the day. Increasing NEAT (nonexercise activity thermogenesis) can boost your daily calorie burn, research has discovered. Part two? Set a timer on your smartphone for every 30 minutes as a reminder to get up and do planks or bridges for 60 seconds straight, recommends Borden. This habit will not only further stoke your fat-burning potential but also stretch and lengthen the psoas and hip flexors so you ward off aches and pains.

As a result of the boost in estrogen levels, women retain more fluid in the days leading up to their period; most will gain a pound or two, says Mary Jane Minkin, MD, clinical professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine. Plus, research shows that we tend to eat more calories—especally from carbs—just before our flow arrives, possibly because fluctuating hormones can make us feel less full after eating.

The solution: In addition to going easy on high-carb, high-salt foods, you can minimize PMS-related bloat by cutting out carbonated beverages and sugar-free gums and candies, says Bonci. Fizzy drinks release carbon dioxide into the gastrointestinal tract, and sugar alcohols used as sweeteners, like sorbitol and mannitol, react with bacteria in the large intestine to produce gas, giving you a distended belly. For a quick deflating fix, Dr. Minkin suggests popping a Gas-X tablet, which contains an ingredient called simethicone: "It breaks up big gas bubbles into smaller ones, which can pass out of your body more easily."

Pregnancy stretches out your rectus abdominis, the two muscles that run down the center of your abdomen from your sternum to the top of your pelvis, says Dr. Minkin. (These are also know as the six-pack muscles.) They require time to tighten again; in fact, abdominal bulge may take as long as nine months to firm up after pregnancy.

The solution: Rebuild you core from the inside out. Add in exercises that target the often overlooked deep muscles, like the pelvic floor, transverse abdominis (behind your obliques), and multifidus (which runs along your spine), advises Fantigassi, while also working the six-pack at the front of the abdominal cavity. Planks are especially good at hitting these muscles, says Dobrosielski, who recommends doing high, rotating planks and plank-ups. Other good moves to include: bird dogs and figure eight lunges. Keep in mind: You might not be able to reestablish your pre-baby belly completely—and that's OK. As Dobrosielski puts it, "Several of the fittest women I know have had babies, and they'd say, 'My abdomen isn't exactly like it used to be.' But anyone who saw them would say, 'I'd do anything to look like that.'"

Add more of these foods to your meal plan to start subtracting inches around the waist.

Up your soluble fiber. Researchers at Wake Forest Baptist Medical Center found that for every 10-gram increase in daily soluble fiber consumed (from foods like fruits, veggies, and beans), visceral fat (the kind that's found deep in the belly) went down by 3.7% over five years.

Get more "good" fat. People who eat foods that are high in monosaturated fat—such as olive oil, nuts, and avocados—are less likely to store fat in the belly than those who consume a high-carb diet, according to a study in Diabetes Care.

Boost calcium intake. "If you're deficient, getting more calcium may help you lose weight," says Collingwood. A 2010 study found that the more calcium women consumed, the less visceral fat they were likely to gain. Good sources: milk, yogurt, cheese, broccoli, and kale.