High-Fiber Diets Reduce Calorie Absorption

People absorb fewer calories overall from a high-fiber diet than from a Western diet rich in processed foods, according to a 2025 Arizona State University-led study. Researchers gave participants both diets with identical proportions of carbohydrates, proteins, and fats, then measured their metabolism inside sealed whole-room calorimeters. Nearly everyone absorbed fewer calories from the high-fiber diet, although participants with methane-producing gut microbes extracted more energy from it than those who produced less methane.

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