Ask Monica: does fiber absorb fat from foods?

Q. Some time ago I remember reading that dietary fiber absorbs some of the fat that would normally be absorbed by the body. If this is true, would it be better for me to eat a salad before or after my main meal?  Secondly, logic tells me that eating a salad after a meal would push the material through my digestive system faster. Is this true?

A. If you are trying to manage your weight, fiber is definitely your friend. But it's not because it acts as a fat-blocker. There's a kernel of truth to this rumor: Fiber can prevent a small amount of fat from being absorbed in the intestines, but the effect is not enough to make a substantial difference in terms of your caloric intake. 

In my opinion, the real  benefit of fiber for weight control is that high fiber foods create a sensation of fullness in your stomach, which can help you eat less.  For this reason, I think  you'd get more benefit from eating your salad before your main meal.  You can enhance the satiating effect of high-fiber foods by drinking water with them. Water "fluffs up" the fiber and makes it take up more room.  (You might also be interested in this article on NutritionData's Fullness Factor.)

As far as fiber "pushing the material through your digestive system faster," that's not quite how it works. Fiber actually slows the transit time of food through the stomach and small intestines, where digestion and absorption take place.  Then, in the large intestines, it helps promote the elimination of waste by keeping things moving through the bowel. In terms of its effect on digestive function, it wouldn't matter whether you ate your salad before or after other foods at the same meal.

For good health, we should all get 25 to 30 grams of fiber a day--but most Americans get only about half that. Use NutritionData's Nutrient Search Tool to find high-fiber foods in any category.