Losing weight is one thing. Maintaining weight loss is quite another. And for many people, keeping the weight off is an even bigger challenge than losing it in the first place.

So what’s the secret?

A new study published in the Journal of the American Medical Association put three diets to the test to determine which holds the key to lasting weight loss. The researchers studied 21 overweight and obese adults who had recently lost at least 12.4% of their body weight. After their initial weight loss, the participants were put on a cycle of three diets, each lasting four weeks, to examine which was the most effective for weight maintenance.

The first was a low-fat diet, similar to the diet recommended by the American Heart Association. Participants were asked to reduce their dietary fat intake and up their intake of whole grains, fruits, and vegetables.

The second diet was modeled on the famous Atkin’s Diet plan. During that phase, participants consumed more protein and fat but drastically cut down their consumption of carbohydrates like breads and pastas.

The third diet was a low-glycemic index plan, a dieting strategy that focuses on regulating the body’s blood sugar levels. Participants were not required to reduce either fat or carbs, but instead placed emphasis on the quality of the carbohydrates they consumed. Grain products and starchy vegetables were replaced with legumes, fruits, other vegetables, and foods loaded with healthy fats.

At the end of the experiment, the low-fat diet proved to be the weakest link in the chain. Dieters on the low-fat plan burned fewer calories than when on either of the other plans, and also experienced changes to certain metabolic factors in their bodies that are generally considered indications of weight regain.

Participants on the low-carb diet burned the most calories, but their diet also caused increases in stress and inflammation in the body. These changes, such as higher levels of the hormone cortisol, are risk factors for health problems like cardiovascular disease.

The low-glycemic index diet came out on top of the experiment, striking a balance between calorie burn and general health. Though it burned fewer calories than the low-carb diet, it burned calories more effectively than the low-fat plan. It also didn’t increase disease-causing stress markers in the body like the low-carb diet.

“In addition to the benefits noted in this study, we believe that low-glycemic-index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which many people find limiting,” said Cara Ebbeling, leader of the study. “Unlike low-fat and low-very-carbohydrate diets, a low-glycemic-index diet doesn’t eliminate entire classes of food, likely making it easier to follow and more sustainable.”

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