By Sarah Gold
Determining how to stave off hunger while on a reduced calorie diet is the million-dollar question in the world of weight management. While there are many theories on how to increase satiety, slowing gastric emptying rate, or the rate at which food leaves the stomach, is a common tactic among many weight loss plans. Fiber, a carbohydrate found mostly in plant foods, is known to slow digestion and is often touted as the not-so-secret ingredient to weight loss.
Diets that contain fiber-rich foods such as fruits, vegetables, whole foods, and legumes have been associated with a decreased risk of obesity among other health benefits. In addition, a significant amount of research over the last 30 years has linked fiber-rich foods to improved glycemic control, increased production of hunger-suppressing hormones in the hours after a meal, reduced production of hunger hormones, and overall increased satiety. In theory, reduced hunger should lead a person to eat less, and ultimately lose weight.
For this reason, fiber has received a lot of attention from dietitians and weight management counselors to food companies and health journalists. And it has begun to show up in unlikely places. A 90-calorie brownie with 20% of your daily fiber needs – who would have thought it possible? Food scientists, that’s who! Food companies are adding synthetic, or functional, fiber to anything from white bread to sugary breakfast cereals and even baked goods. You can now get 100% of the recommended 25-30g of dietary fiber per day without ever eating a fruit, vegetable, or whole grain. However, the question that remains is, does this added fiber actually aid weight-loss?
There are two types of naturally occurring fiber: soluble and insoluble. Both are found in plant foods, insoluble in the skins of fruits and vegetables, and soluble found in oats, legumes, and whole grains. Researchers have tested the effect of synthetic soluble and insoluble fibers on satiety with mixed results. For example, beta-glucan (the kind of fiber found in oats) has been shown to have some effect on satiety, while inulin (found in plant roots) has been ineffective. There are a number of different synthetic fibers that food companies use to boost the fiber content of food, so it’s difficult to know if the product your buying will actually offer any benefit. In addition, studies that have tested the effect of supplemental fiber on weight management have been less than promising.
When it comes to weight management, fiber-rich foods certainly play a role. But is fiber the magic ingredient we’ve all been looking for? Probably not. Much of the research that links fiber-rich diets to lower weight are population studies, which are not able to completely control for other lifestyle factors that play a role in weight management such as physical activity and presence of other foods in the diet. In addition, many foods that naturally contain fiber also have a high percentage of water, which can also play a role in satiety. If you’re looking to reduce calories and control hunger, stick with whole foods that contain fiber such as whole-grains, fruits, vegetables, and legumes.
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Lyon, M. & Kacnik, V. (2012). Is there a place for dietary fiber supplements in weight loss? Current Obesity Reports; 1(2): 59-67.