A couple of months ago, your diet was going great. You were dropping pounds, fitting back into your favorite shirts, and your abs were actually starting to emerge from hiding. 

Now, you've stopped losing flab— or even worse, you've started packing it back on— even though you are doing the exact same thing that was slimming you down before. It turns out, doing the same thing is the problem. Here's how to switch up your weight loss strategy to keep your belt size moving in the right direction.

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1. Cut More Calories

Contrary to what you probably think (or hope), your metabolism doesn't speed up as you lose weight. It slows down. Way down. After all, it takes less fuel to run a moped than it does to run a semi, says Christopher Ochner, Ph.D., nutrition expert for USANA and weight-loss expert at Mount Sinai Hospital in New York City. Meanwhile, when you start losing weight, if it's in a slow, steady, and healthy way, your body goes into starvation mode. "When people lose just 10 percent body fat, their bodies react very similarly to those of starving individuals," says Lisa Neff, M.D., an endocrinologist at the Center for Lifestyle Medicine at Northwestern Medical Group. 

Daily caloric burn becomes about 15 percent lower than it should be for the average guy of your weight, and your muscles use 25 percent fewer calories than they used to. That means every workout burns only three-fourths of the calories it did before, she says.

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So, if you're eating the same number of calories on Day 30 of your diet as you did on Day 1 of your diet, you may actually be taking in more calories than you're burning at your new weight, says Jim White, R.D., owner of Jim White Fitness training studios and a spokesperson for the Academy of Nutrition and Dietetics. He recommends getting your resting metabolism checked (most high-end gyms offer the service) every two to three months when you're losing weight. Or, if you're not keen on the idea, just try shaving an extra 200 calories from your daily intake and see how the scale reacts, he says.

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2. Eat More Protein

To continually cut calories without 1) feeling miserably hungry and 2) having your metabolism drop through the floor, you're going to need more protein. Protein is critical to feeling fuller longer and helping preserve calorie-burning lean muscle mass, Ochner says.

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In one Nutrition & Metabolism study, when dieters cut 500 calories from their daily intake for 12 weeks, those who took a protein supplement lost more weight from fat and less from muscle. FYI, a pound of fat burns about two calories a day. A pound of muscle burns six.

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3. Do a New Workout

You body is a master adaptor. After every workout, your body gets better, stronger, and more efficient. While that's a good thing if you want to improve your mile time or dead-lift PR, it's a bad thing for burning calories and building muscle. "I see guys in the gym performing the same workouts year after year— with the same bodies. Their bodies never improve," White says. 

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To keep your body guessing and prevent wasting your gym time, switch up your workout's rep and set scheme about every six weeks, so that you are continually lifting more weight, building more muscle, and burning more calories, he says.

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