Comparing low-carb and low-fat diets for weight loss Original paper

Low-fat diets used to be the mainstay of weight loss attempts, but low-carbohydrate diets have recently demonstrated efficacy, too. How do the two compare?

In this four-week crossover study, 17 participants with obesity were fed three isocaloric diets in random order, separated by four weeks of washout. The diets were: a carbohydrate-restricted diet with 10% carbs, 50% fat, and 40% protein and high levels of plant foods and mushrooms; a carbohydrate-restricted diet with 10% carbs, 60% fat, and 30% protein and more animal foods; and a low-fat diet with 61% carbs, 21% fat, and 18% protein. Body composition and fasting blood samples were measured at baseline and at the end of each diet.

While every dietary intervention resulted in participants losing weight compared to baseline, the plant-heavy low-carb diet produced significantly more weight loss compared to the low-fat diet, with no changes in body water content. Similarly, every group lost fat mass, but only the plant-heavy low-carb diet resulted in a reduction in body fat percentage. Notably, participants on the plant-heavy low-carb diet did lose more lean mass compared to the low-fat diet, although this may be the result of muscle glycogen depletion. Compared to baseline, β-hydroxybutyrate and insulin sensitivity increased during both low-carb diets, and fasting insulin, cholesterol, and leptin was reduced during every diet. Overall, it seems that each diet resulted in generally favorable effects, although the plant-heavy low-carb group may have exerted the greatest effects.

The plant-heavy low-carb diet emphasized eating mushrooms, and this study was funded by the Mushroom Council, which is a U.S.-based organization that promotes the sale and consumption of mushrooms. It’s not clear how much this funding source affected these findings, but it’s worth keeping in mind.