A single dietary change can increase our resting metabolic rate.
How to Boost Fat Burning by 25%
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.
We now know why fiber-rich foods can have such a powerful effect on our weight. The evidence for the role of fiber in weight control started with so-called ecological studies. These involve comparing population averages, and researchers noted that populations with extraordinary fiber intakes tend to have negligible obesity rates. For example, the average Pima Indian in Mexico eating their traditional high-fiber diet centered around the “three sisters” (corn, beans, and squash) is normal weight, but the average Pima on U.S. reservations has obesity. The problem with dealing with population averages is that we don’t know if the individuals eating the higher fiber diets are themselves necessarily the ones protected from obesity.
What do we see in cohort studies, where individuals and their diets are followed over time? A cohort study of overweight youth found that the amount of fiber found in a single half-cup daily serving of beans, about six grams, over about a two-year period, was associated with a profound 25% difference in abdominal obesity. In about the same timeframe, in middle-aged women, each two-gram increase in daily fiber was associated with a weight decrease of about a pound (0.45 kg). The postpartum period seems to be a critical time for women to be at risk of retaining the weight put on during pregnancy. A study of hundreds of new moms followed for the first five months found that inadequate fiber intake appeared to increase obesity risk by 24%. And it’s not just women. A cohort that included tens of thousands of men followed for years concluded that an increase in fiber consumption of just 10 grams a day may prevent about 10% of weight gain within the population.
Overall, the evidence from these kinds of observational studies is strong: “Increasing consumption of dietary fiber with fruits, vegetables, whole grains, and legumes across the life cycle is a critical step in stemming the epidemic of obesity.” These studies can control for nondietary influences such as physical activity by equipping people with gadgets to measure their movement. But there may be uncontrolled confounding dietary factors. Think about the list of high-fiber foods—fruits, vegetables, whole grains, and beans. Maybe fiber intake is just a marker for the intake of healthy foods, and there are dozens of reasons why eating whole plant foods could lead to weight loss that have nothing to do with fiber. To know if there’s a cause-and-effect relationship between fiber and weight loss, you need to put it to the test in interventional trials.
That’s where colonic infusions can come in handy.
In a randomized, double-blind, placebo-controlled crossover study, researchers showed that people’s metabolism can be boosted within 30 minutes of an infusion into their rectums of short-chain fatty acids––the molecules our gut bacteria make when we feed them fiber. The study used the amounts we’d expect to create ourselves just from eating a high-fiber diet. Not only did the study participants get an increase in their resting metabolic rate (the amount of calories burned just by existing), but specifically their fat oxidation shot up as well, increasing the amount of fat they were burning by more than 25%. This translates to about an extra third of a pat of butter’s worth of fat burned off their body within two hours of the infusion.
Colonic catheters aside, we can get short-chain fatty acids directly, and get the same little bump in resting metabolic rate and whole-body fat breakdown, in addition to a decrease in appetite. So again, fiber may work on both sides of the energy balance equation. But does that decreased appetite actually translate into eating less? We’ll find out next.
Please consider volunteering to help out on the site.
- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001;59(5):129-139.
- Davis JN, Alexander KE, Ventura EE, Toledo-Corral CM, Goran MI. Inverse relation between dietary fiber intake and visceral adiposity in overweight Latino youth. Am J Clin Nutr. 2009;90(5):1160-1166.
- Tucker LA, Thomas KS. Increasing total fiber intake reduces risk of weight and fat gains in women. J Nutr. 2009;139(3):576-581.
- Drehmer M, Camey SA, Nunes MA, et al. Fibre intake and evolution of BMI: from pre-pregnancy to postpartum. Public Health Nutr. 2013;16(8):1403-1413.
- Du H, van der A DL, Boshuizen HC, et al. Dietary fiber and subsequent changes in body weight and waist circumference in European men and women. Am J Clin Nutr. 2010;91(2):329-336.
- Slavin JL. Dietary fiber and body weight. Nutrition. 2005;21(3):411-418.
- Canfora EE, van der Beek CM, Jocken JWE, et al. Colonic infusions of short-chain fatty acid mixtures promote energy metabolism in overweight/obese men: a randomized crossover trial. Sci Rep. 2017;7(1):2360.
- van der Beek CM, Canfora EE, Lenaerts K, et al. Distal, not proximal, colonic acetate infusions promote fat oxidation and improve metabolic markers in overweight/obese men. Clin Sci (Lond). 2016;130(22):2073-2082.
- Chambers ES, Byrne CS, Aspey K, et al. Acute oral sodium propionate supplementation raises resting energy expenditure and lipid oxidation in fasted humans. Diabetes Obes Metab. 2018;20(4):1034-1039.
- Alhabeeb H, Chambers ES, Frost G, Morrison DJ, Preston T. Inulin propionate ester increases satiety and decreases appetite but does not affect gastric emptying in healthy humans. Proc Nutr Soc. 2014;73(OCE1):E21.
- Polyviou T, MacDougall K, Chambers ES, et al. Randomised clinical study: inulin short-chain fatty acid esters for targeted delivery of short-chain fatty acids to the human colon. Aliment Pharmacol Ther. 2016;44(7):662-672.
- Chambers ES, Viardot A, Psichas A, et al. Targeted delivery of propionate to the colon stimulates the release of anorectic gut hormones and suppresses appetite in humans. Proc Nutr Soc. 2014;73(OCE1):E15.
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.
We now know why fiber-rich foods can have such a powerful effect on our weight. The evidence for the role of fiber in weight control started with so-called ecological studies. These involve comparing population averages, and researchers noted that populations with extraordinary fiber intakes tend to have negligible obesity rates. For example, the average Pima Indian in Mexico eating their traditional high-fiber diet centered around the “three sisters” (corn, beans, and squash) is normal weight, but the average Pima on U.S. reservations has obesity. The problem with dealing with population averages is that we don’t know if the individuals eating the higher fiber diets are themselves necessarily the ones protected from obesity.
What do we see in cohort studies, where individuals and their diets are followed over time? A cohort study of overweight youth found that the amount of fiber found in a single half-cup daily serving of beans, about six grams, over about a two-year period, was associated with a profound 25% difference in abdominal obesity. In about the same timeframe, in middle-aged women, each two-gram increase in daily fiber was associated with a weight decrease of about a pound (0.45 kg). The postpartum period seems to be a critical time for women to be at risk of retaining the weight put on during pregnancy. A study of hundreds of new moms followed for the first five months found that inadequate fiber intake appeared to increase obesity risk by 24%. And it’s not just women. A cohort that included tens of thousands of men followed for years concluded that an increase in fiber consumption of just 10 grams a day may prevent about 10% of weight gain within the population.
Overall, the evidence from these kinds of observational studies is strong: “Increasing consumption of dietary fiber with fruits, vegetables, whole grains, and legumes across the life cycle is a critical step in stemming the epidemic of obesity.” These studies can control for nondietary influences such as physical activity by equipping people with gadgets to measure their movement. But there may be uncontrolled confounding dietary factors. Think about the list of high-fiber foods—fruits, vegetables, whole grains, and beans. Maybe fiber intake is just a marker for the intake of healthy foods, and there are dozens of reasons why eating whole plant foods could lead to weight loss that have nothing to do with fiber. To know if there’s a cause-and-effect relationship between fiber and weight loss, you need to put it to the test in interventional trials.
That’s where colonic infusions can come in handy.
In a randomized, double-blind, placebo-controlled crossover study, researchers showed that people’s metabolism can be boosted within 30 minutes of an infusion into their rectums of short-chain fatty acids––the molecules our gut bacteria make when we feed them fiber. The study used the amounts we’d expect to create ourselves just from eating a high-fiber diet. Not only did the study participants get an increase in their resting metabolic rate (the amount of calories burned just by existing), but specifically their fat oxidation shot up as well, increasing the amount of fat they were burning by more than 25%. This translates to about an extra third of a pat of butter’s worth of fat burned off their body within two hours of the infusion.
Colonic catheters aside, we can get short-chain fatty acids directly, and get the same little bump in resting metabolic rate and whole-body fat breakdown, in addition to a decrease in appetite. So again, fiber may work on both sides of the energy balance equation. But does that decreased appetite actually translate into eating less? We’ll find out next.
Please consider volunteering to help out on the site.
- Howarth NC, Saltzman E, Roberts SB. Dietary fiber and weight regulation. Nutr Rev. 2001;59(5):129-139.
- Davis JN, Alexander KE, Ventura EE, Toledo-Corral CM, Goran MI. Inverse relation between dietary fiber intake and visceral adiposity in overweight Latino youth. Am J Clin Nutr. 2009;90(5):1160-1166.
- Tucker LA, Thomas KS. Increasing total fiber intake reduces risk of weight and fat gains in women. J Nutr. 2009;139(3):576-581.
- Drehmer M, Camey SA, Nunes MA, et al. Fibre intake and evolution of BMI: from pre-pregnancy to postpartum. Public Health Nutr. 2013;16(8):1403-1413.
- Du H, van der A DL, Boshuizen HC, et al. Dietary fiber and subsequent changes in body weight and waist circumference in European men and women. Am J Clin Nutr. 2010;91(2):329-336.
- Slavin JL. Dietary fiber and body weight. Nutrition. 2005;21(3):411-418.
- Canfora EE, van der Beek CM, Jocken JWE, et al. Colonic infusions of short-chain fatty acid mixtures promote energy metabolism in overweight/obese men: a randomized crossover trial. Sci Rep. 2017;7(1):2360.
- van der Beek CM, Canfora EE, Lenaerts K, et al. Distal, not proximal, colonic acetate infusions promote fat oxidation and improve metabolic markers in overweight/obese men. Clin Sci (Lond). 2016;130(22):2073-2082.
- Chambers ES, Byrne CS, Aspey K, et al. Acute oral sodium propionate supplementation raises resting energy expenditure and lipid oxidation in fasted humans. Diabetes Obes Metab. 2018;20(4):1034-1039.
- Alhabeeb H, Chambers ES, Frost G, Morrison DJ, Preston T. Inulin propionate ester increases satiety and decreases appetite but does not affect gastric emptying in healthy humans. Proc Nutr Soc. 2014;73(OCE1):E21.
- Polyviou T, MacDougall K, Chambers ES, et al. Randomised clinical study: inulin short-chain fatty acid esters for targeted delivery of short-chain fatty acids to the human colon. Aliment Pharmacol Ther. 2016;44(7):662-672.
- Chambers ES, Viardot A, Psichas A, et al. Targeted delivery of propionate to the colon stimulates the release of anorectic gut hormones and suppresses appetite in humans. Proc Nutr Soc. 2014;73(OCE1):E15.
Motion graphics by Avo Media
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How to Boost Fat Burning by 25%
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