While probiotics encourage the growth of good bacteria, prebiotics feed the ones you already have. When you eat prebiotic foods like onions and leeks, they produce butyrate, a metabolic wonder drug that improves insulin sensitivity and increases the amount of fat you burn, says Rafael Kellman, M.D., author of The Microbiome Diet. Now that it's summer, pop either on the grill to bring out their sweetness. Drizzle with olive oil, salt, and pepper and cook until golden.

Which means, sadly, the more glasses of rose and chocolate-coated pretzels you eat, the longer it will take to reach your flatter belly goals. “When you digest large amounts of calories, your body allocates some of these to functional systems which work to keep you alive (think the brain, muscles and organs),” says Belalij. “It also uses it to fill up energy stores. Any excess is then stored in fat cells around the body – typically being those of the belly.”
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