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Are Calories From Fat, Protein and Carbs Equal?

Scientists study how your body processes calories from different food sources. Which combo is the best for weight loss?

When it comes to keeping the weight off, not all calories are equal, say researchers from Children’s Hospital Boston. Some nutritionists believe that calories from fat, protein, and carbs affect your metabolism—also known as energy expenditure—in the same way during the maintenance of weight loss.

In a new study, researchers tested this idea by monitoring 21 adults throughout a rigorous weight loss program. After a weight monitoring phase, participants lost 10 to 15 percent of their body weight over 12 weeks. This involved eating pre-prepared meals containing 60 percent of their usual calorie intake.

The next step was testing three diets to see which might help people maintain weight loss by keeping their metabolism going. Avoiding a weight rebound is difficult for many people because their metabolism is slower after losing weight. All participants completed four weeks on each of the three diets.

Energy expenditure decreased the most with a low-fat diet, and the least with a very low-carb diet—modeled on the Atkins diet. A low-glycemic index diet—one favoring foods that don’t cause a spike in blood sugar—slowed the metabolism slightly more than the high-protein diet, but showed fewer signs of increased stress hormones.

One drawback of the study, published in the Journal of the American Medical Association, was that participants were on very restricted diets, which helped them lose and maintain weight loss. More research is needed, especially under real-world conditions.

The bottom line is that if you want to lose weight and keep it off, you need to eat less. It may also be useful to avoid high-glycemic index foods—such as refined sugars and processed foods. These could slow down your metabolism and cause you to regain your lost weight.

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