If insulin is the mother of fat storage, glucagon is the father of fat burning. One critical way to increase this hormone is to eat more protein, says Teta. “Protein is the most powerful fat-loss tool we have,” he says. Protein intake also suppresses the hunger hormone ghrelin and helps release muscle- building hormones, like testosterone, enabling people to avoid the muscle-wasting (what he calls the “skinny-fat” look) and sluggish metabolism that often accompany calorie-restriction diets.

But not all protein is created equal. In Hu’s 2011 study, eating red meat, usually higher in calories and saturated fat, was strongly associated with weight gain over four-year periods. Another recently published study found that those who ate a diet low in carbs but higher in animal protein had an increased mortality risk, particularly from cancer and cardiovascular disease, while those who ate a low-carb diet high in plant-based protein had a lower mortality risk. “A lot of people think a low-carb diet needs to be loaded with steaks and bacon. That’s not the case,” says Hu.

When trying to lose weight and balance blood sugar, Teta recommends going easy on beans, which are high in protein but can be as much as 70 percent starch, and opting for lean poultry, fish, eggs, and game meat. Vegans should consider adding a rice, hemp, or nut protein powder supplement to their diets.