Our gut can be sedentary too—unless we feed it fiber.
Use Fiber to Burn Calories in Your Sleep with an Intestinal Workout
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Fiber can literally help flush calories away, assisting with weight management. A review entitled “Food fibre as an obstacle to energy intake” summarized the four Ds by which dietary fiber results in reduced caloric intake. There’s the dilution of calories by expanding the volume of food, distention of the stomach through fluid absorption, delay in stomach emptying of the gelled mass, and dumping of calories by blocking the absorption of other macronutrients. That fourth D triggers a fifth phenomenon, known as the ileal brake. As Dr. Greger has covered, the ileum is the last part of the small intestine before it empties into the colon. When undigested nutrients are detected that far down, the body puts the brakes on further eating by curbing our appetite.
So, there are lots of ways eating more fiber can help with weight regulation. Across more than 10 weight-loss studies, those randomized to consume higher-fiber diets lost more weight, even when calorie intake was fixed. So, more weight loss even when prescribed the same number of calories. If it wasn’t the “calories in” side of the equation, was it the “calories out”? Normally that means things like exercise, but in the case of high-fiber diets, there literally are calories out, as in out the other end and flushed down the toilet. But the same-calorie, higher-fiber groups were losing more weight than could be accounted for––even after taking into account the excess calorie dumping. Where were the calories going?
To solve the mystery of the missing calories, researchers fed people different amounts of fiber, and sealed them in an airtight chamber called a whole-body calorimeter to closely monitor their metabolic rate. Those with more fiber in their system were burning more calories even in their sleep! Only about 2% more, but that translated into burning almost 50 more calories a day without getting off the couch.
For people on long-term fiber-rich diets, they figured that all that fiber might bulk up their intestinal lining, which is a highly metabolically-active tissue. Why were they spontaneously burning off more energy even when they were asleep? It turns out all that extra fiber may have been giving their gut a workout.
Our intestines are muscular tubes. So, our small intestine is like 20 feet (6.10 m) of muscle, which contracts in waves to move food along. But fiber-depleted foods don’t offer much resistance. The apple juice and Wonder Bread get absorbed almost immediately, and don’t put up much resistance. It’s like weight lifting with a barbell made out of Styrofoam. Not very effective.
Researchers had people swallow long strings of electrodes to measure the electrical activity of the muscular contractions of the intestines of those eating low-fiber meals versus high-fiber meals. The individuals eating more fiber not only had stronger, faster, longer contractions, but reduced the periods of intestinal inactivity. Turns out our gut can be sedentary, too. But if we eat lots of fiber-rich foods, we can be asleep and our gut will still be exercising all night long.
Please consider volunteering to help out on the site.
- Heaton KW. Food fibre as an obstacle to energy intake. Lancet. 1973;2(7843):1418-1421.
- van Avesaat M, Troost FJ, Ripken D, Hendriks HF, Masclee A a. M. Ileal brake activation: macronutrient-specific effects on eating behavior? Int J Obes (Lond). 2015;39(2):235-243.
- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001;59(5):129-139.
- Castiglia-Delavaud C, Verdier E, Besle JM, et al. Net energy value of non-starch polysaccharide isolates (Sugarbeet fibre and commercial inulin) and their impact on nutrient digestive utilization in healthy human subjects. Br J Nutr. 1998;80(4):343-352.
- Cherbut C, Bruley des Varannes S, Schnee M, Rival M, Galmiche JP, Delort-Laval J. Involvement of small intestinal motility in blood glucose response to dietary fibre in man. Br J Nutr. 1994;71(5):675-685.
Motion graphics by Avo Media
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Fiber can literally help flush calories away, assisting with weight management. A review entitled “Food fibre as an obstacle to energy intake” summarized the four Ds by which dietary fiber results in reduced caloric intake. There’s the dilution of calories by expanding the volume of food, distention of the stomach through fluid absorption, delay in stomach emptying of the gelled mass, and dumping of calories by blocking the absorption of other macronutrients. That fourth D triggers a fifth phenomenon, known as the ileal brake. As Dr. Greger has covered, the ileum is the last part of the small intestine before it empties into the colon. When undigested nutrients are detected that far down, the body puts the brakes on further eating by curbing our appetite.
So, there are lots of ways eating more fiber can help with weight regulation. Across more than 10 weight-loss studies, those randomized to consume higher-fiber diets lost more weight, even when calorie intake was fixed. So, more weight loss even when prescribed the same number of calories. If it wasn’t the “calories in” side of the equation, was it the “calories out”? Normally that means things like exercise, but in the case of high-fiber diets, there literally are calories out, as in out the other end and flushed down the toilet. But the same-calorie, higher-fiber groups were losing more weight than could be accounted for––even after taking into account the excess calorie dumping. Where were the calories going?
To solve the mystery of the missing calories, researchers fed people different amounts of fiber, and sealed them in an airtight chamber called a whole-body calorimeter to closely monitor their metabolic rate. Those with more fiber in their system were burning more calories even in their sleep! Only about 2% more, but that translated into burning almost 50 more calories a day without getting off the couch.
For people on long-term fiber-rich diets, they figured that all that fiber might bulk up their intestinal lining, which is a highly metabolically-active tissue. Why were they spontaneously burning off more energy even when they were asleep? It turns out all that extra fiber may have been giving their gut a workout.
Our intestines are muscular tubes. So, our small intestine is like 20 feet (6.10 m) of muscle, which contracts in waves to move food along. But fiber-depleted foods don’t offer much resistance. The apple juice and Wonder Bread get absorbed almost immediately, and don’t put up much resistance. It’s like weight lifting with a barbell made out of Styrofoam. Not very effective.
Researchers had people swallow long strings of electrodes to measure the electrical activity of the muscular contractions of the intestines of those eating low-fiber meals versus high-fiber meals. The individuals eating more fiber not only had stronger, faster, longer contractions, but reduced the periods of intestinal inactivity. Turns out our gut can be sedentary, too. But if we eat lots of fiber-rich foods, we can be asleep and our gut will still be exercising all night long.
Please consider volunteering to help out on the site.
- Heaton KW. Food fibre as an obstacle to energy intake. Lancet. 1973;2(7843):1418-1421.
- van Avesaat M, Troost FJ, Ripken D, Hendriks HF, Masclee A a. M. Ileal brake activation: macronutrient-specific effects on eating behavior? Int J Obes (Lond). 2015;39(2):235-243.
- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001;59(5):129-139.
- Castiglia-Delavaud C, Verdier E, Besle JM, et al. Net energy value of non-starch polysaccharide isolates (Sugarbeet fibre and commercial inulin) and their impact on nutrient digestive utilization in healthy human subjects. Br J Nutr. 1998;80(4):343-352.
- Cherbut C, Bruley des Varannes S, Schnee M, Rival M, Galmiche JP, Delort-Laval J. Involvement of small intestinal motility in blood glucose response to dietary fibre in man. Br J Nutr. 1994;71(5):675-685.
Motion graphics by Avo Media
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Use Fiber to Burn Calories in Your Sleep with an Intestinal Workout
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
For more on fiber, see:
- Is Fiber an Effective Anti-Inflammatory?
- How to Lower Lead Levels with Diet: Thiamine, Fiber, Iron, Fat, Fasting?
- Using Prebiotics, Intact Grains, Thylakoids, and Greens to Boost Our GLP-1 for Weight Loss
- Does Fiber Really Prevent Diverticulosis?
For even more on weight control, go to your local public library and check out my book, How Not to Diet, available in print, e-book, and audio. (All proceeds I receive from the book are donated directly to charity.)
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