One side effect of eating too much sugar is that you’re programmed to overeat and gain belly fat. Why? While sugar drives up insulin production, it fails to trigger another hormone in your body that helps control appetite: leptin. Without enough leptin, your “signaling center” breaks down, and you quickly end up with a traffic jam of food in your body ready to get stored as fat. Where this fat gets deposited depends on your genetics, but most of us start storing it in our midsection. Research published in the American Journal of Clinical Nutrition confirmed that foods sweetened with fructose, sucrose, glucose, and high-fructose corn syrup all have the same effect on leptin—they fail to produce it. Another study done at the University of California, Los Angeles (UCLA), discovered the same about lactose (milk sugar).

What happens when you don’t have leptin? Research at the Albert Einstein College of Medicine in New York showed that when leptin was produced, it directly contributed to a decrease in abdominal fat. Without the right amounts of leptin, your body is programmed to store fat in your abdominal region. The most revealing studies were published in The Journal of Clinical Endocrinology & Metabolism and the Annals of the New York Academy of Sciences, which showed that the proper levels of leptin decreased abdominal fat by 32 percent and an extraordinary 62 percent, respectively. This means that making sure your diet contains foods that will regularly stimulate leptin production is essential to belly fat loss. This is why it’s important to eat foods that trigger leptin—such as proteins, fats, and complex carbs—so you’re not set up to overeat.