Scientists have successfully used a drug to trick mice into revving up their metabolisms. The compound prompts the body to act as though it's about to have a meal, even if the meal isn't forthcoming. The researchers behind the medication, led by Michael Downes and Ronald Evans at the Salk Institute, are preparing to move the compound forward to human testing.

Diet drugs are of particular interest to pharma companies In their tests, the drug stopped weight gain in obese mice, according to a report in Nature Medicine. That's not all, though. It lowered cholesterol, a known contributor to heart disease — and also helped the animals control their blood sugar, which is key for preventing metabolic syndrome and, eventually, Type 2 diabetes. The difference in weight gain wasn't because the animals were eating less.

What's more interesting, though, is the compound's effects on fat. The familiar kind of fat — white fat —stores energy. But another kind, called brown fat, helps burn it. Until 2009, scientists thought that although babies had brown fat, adults didn't. But then three independent research groups found brown fat in adults, too. Today's study drug helps make the brown fat even more efficient at burning calories — and helped convert white fat to brown fat as well.

Diet drugs are of particular interest to pharmaceutical companies, since more than a third of adults in the US are obese, according to the CDC. Another 29 million adults — almost 10 percent of the population — have type 2 diabetes, a disease where blood glucose levels become abnormal. Being overweight or obese increases the likelihood that someone will develop type 2 diabetes.

The discovery stems from research into the farensoid X receptor (FXR), a protein which the body switches on at the beginning of a meal. It also plays a role in food digestion; what's more, it changes blood sugar levels and triggers the body to burn some fat in preparation for the meal that is about to take place. Though other labs have tried to use the FXR pathway to develop weight-loss drugs, the protein controls so many pathways that it can cause side-effects.

The new compound, though, is meant to target only the receptors in the intestines. Preventing the drug from hitting the bloodstream — and then being carried throughout the entire body — may make FXR a feasible weight-loss target, the scientists wrote. The researchers have started the process of putting together a trial in humans, according to a press release from the Salk Institute.