All four of the study diets called for 20 grams of daily fiber, which falls short of the daily intake recommended by the U.S. Institute of Medicine of approximately 35 grams (1.2 ounces) for men and 25 grams (0.9 ounce) for women.
Roberts says that studies she has led show that the more fiber one eats daily (up to about 50 grams, or 1.8 ounces), the more weight he or she is likely to lose. She speculates that is because fiber—which is found in veggies, fruit and whole grains—creates the sensation of fullness after eating by activating stretch receptors, nerve cells that are probably part of the group of signals sending the “I am full” message to the brain, in the digestive tract; it also slows digestion, extending the time that nutrients are dribbling into the blood stream from the intestine, which may lead to feelings of satiety. She notes that the average daily fiber intake in the U.S. is around 13 to 15 grams (0.5 ounce).
So what’s the best way to slim down? “Focus on high-fiber, minimally processed, plant-based foods,” Gardner says, “which translates into lots of vegetables, beans, nuts and seeds, whole grains, and fruits.”