Are there benefits to giving yourself a bigger daily break from eating?
Time-Restricted Eating Put to the Test
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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.
The reason many blood tests are taken before eating after an overnight fast is that meals can tip our system out of balance, bumping up certain biomarkers for disease such as blood sugars, insulin, cholesterol, and triglycerides. Yet fewer than 1 in 10 Americans may even make it 12 hours without eating. As evolutionarily unnatural as eating three meals a day is, most of us are eating even more than that. One study using a smartphone app to record more than 25,000 eating events found that people tended to eat about every 3 hours over an average span of about 15 hours a day. Might it be beneficial to give our bodies a bigger break?
Time-restricted feeding is “defined as fasting for periods of at least 12 hours but less than 24 hours.” This involves trying to confine calorie intake to a set window of time, typically 3–4 hours, 7–9 hours, or 10–12 hours a day, resulting in a daily fast lasting 12-21 hours. When mice are restricted to a daily feeding window, they gain less weight even when fed the exact same amount. Rodents have such high metabolisms, though, that a single day of fasting can starve away as much as 15 percent of their lean body mass. This makes it difficult to extrapolate from mouse models. You don’t know what happens in humans until you put it to the test.
The drop-out rates in time-restricted feeding trials certainly appear lower than most prolonged forms of intermittent fasting, suggesting it’s more easily tolerable. But does it work? If you have people even just stop eating between 7 p.m. and 6 a.m. for two weeks, they lose about a pound each week, compared to no time restriction. Note: no additional instructions or recommendations were given on the amount or type of food consumed; no gadgets, calorie counting, or record-keeping. They were just told to limit their food intake to the hours of 6 a.m. through 7 p.m., a simple intervention, easy to understand and implement.
The next logical step was to try putting it to the test for months instead of just weeks. Obese men and women were asked to restrict eating to the eight-hour window between 10 a.m. and 6 p.m. Twelve weeks later, they had lost seven pounds. This deceptively simple intervention may be operating from a number of different angles. People tend to eat more food later in the day, and higher-fat foods later in the day. By eliminating eating in the late evening hours, one removes prime-time snacking on the couch, a high-risk time for overeating. And indeed, during the no-eating-after-7-p.m. study, the subjects were inadvertently eating about 250 fewer calories a day. Then, there are also the chronobiological benefits of avoiding late-night eating.
I’m going to do a whole series of videos about the role our circadian rhythms have in the obesity epidemic, how the timing of meals can be critical, and how we can match meal timing to our body clocks. Just to give you a taste, the exact same number of calories at dinner is significantly more fattening than the same number of calories eaten at breakfast.
Calories in the morning cause less weight gain than the same calories given in the evening. A diet with a bigger breakfast causes more weight loss than the same exact diet with a bigger dinner. Nighttime snacks are more fattening than the same snacks in the daytime. Thanks to our circadian rhythms, metabolic slowing, hunger, carbohydrate intolerance, triglycerides, and a propensity for weight gain are all things that go bump in the night.
What about the fasting component of time-restricted feeding? There’s already the double benefit of fewer calories and avoiding night-time eating. Does the fact that you’re fasting for 11 or 16 hours a day play any role, considering the average person may only make it about 9 hours a day without eating? How would you design an experiment to test that? What if you randomized people into two groups, and forced both groups to eat the same number of calories a day and both to eat late into the evening, but with one group fasting even longer—20 hours? That’s exactly what researchers at the USDA and National Institute of Aging did.
Men and women were randomized to eat three meals a day, or to fit all those same calories into a four-hour window between 5 p.m. and 9 p.m. and fast the rest of the day. If the weight-loss benefits from the other two time-restricted feeding studies was due to the passive calorie restriction or avoidance of late night eating, then presumably both these groups should end up the same, because they’re both eating the same amount, and they’re both eating late. But that’s not what happened. After eight weeks, the time-restricted feeding group ended up with nearly five pounds less body fat. About the same number of calories, but they lost more weight. A similar study with an eight-hour window resulted in three pounds more fat loss. So, there does seem to be something to giving your body daily breaks from eating around the clock.
Because that four-hour window was at night, though, they suffered the chronobiological consequences—significant elevations in blood pressures and cholesterol levels—despite the weight loss. The best of both worlds was demonstrated in 2018: early time-restricted feeding, eating with a narrow window earlier in the day, which we’ll cover next.
Please consider volunteering to help out on the site.
- Gill S, Panda S. A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metab. 2015;22(5):789–798.
- Anton SD, Moehl K, Donahoo WT, et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring). 2018;26(2):254-268.
- Rothschild J, Hoddy KK, Jambazian P, Varady KA. Time-restricted feeding and risk of metabolic disease: a review of human and animal studies. Nutr Rev. 2014;72(5):308-18.
- Hatori M, Vollmers C, Zarrinpar A, et al. Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet. Cell Metab. 2012;15(6):848-60.
- Lai M, Chandrasekera PC, Barnard ND. You are what you eat, or are you? The challenges of translating high-fat-fed rodents to human obesity and diabetes. Nutr Diabetes. 2014;4:e135.
- Lecheminant JD, Christenson E, Bailey BW, Tucker LA. Restricting night-time eating reduces daily energy intake in healthy young men: a short-term cross-over study. Br J Nutr. 2013;110(11):2108-13.
- Gabel K, Hoddy KK, Haggerty N, et al. Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutr Healthy Aging. 2018;4(4):345-353.
- Jiang P, Turek FW. Timing of meals: when is as critical as what and how much. Am J Physiol Endocrinol Metab. 2017;312(5):E369-E380.
- Laermans J, Depoortere I. Chronobesity: role of the circadian system in the obesity epidemic. Obes Rev. 2016;17(2):108-25.
- Hutchison AT, Wittert GA, Heilbronn LK. Matching Meals to Body Clocks-Impact on Weight and Glucose Metabolism. Nutrients. 2017;9(3).
- Hirsch EHE, Halberg F, Goetz FC, et al. Body weight change during 1 week on a single daily 2000-calorie meal consumed as breakfast (B) or dinner (D). Chronobiologia 1975;2(suppl 1):31–2.
- Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring). 2013;21(12):2504-12.
- Hibi M, Masumoto A, Naito Y, et al. Nighttime snacking reduces whole body fat oxidation and increases LDL cholesterol in healthy young women. Am J Physiol Regul Integr Comp Physiol. 2013;304(2):R94-R101.
- Morris CJ, Garcia JI, Myers S, Yang JN, Trienekens N, Scheer FA. The Human Circadian System Has a Dominating Role in Causing the Morning/Evening Difference in Diet-Induced Thermogenesis. Obesity (Silver Spring). 2015;23(10):2053-8.
- Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14(1):290. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males
- Stote KS, Baer DJ, Spears K, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. 2007;85(4):981-8.
- Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018;27(6):1212-1221.e3.
Image credit: Monoar Rahman Rony via pixabay. Image has been modified.
Video includes graphics from Vecteezy.com
Motion graphics by Avocado Video
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.
The reason many blood tests are taken before eating after an overnight fast is that meals can tip our system out of balance, bumping up certain biomarkers for disease such as blood sugars, insulin, cholesterol, and triglycerides. Yet fewer than 1 in 10 Americans may even make it 12 hours without eating. As evolutionarily unnatural as eating three meals a day is, most of us are eating even more than that. One study using a smartphone app to record more than 25,000 eating events found that people tended to eat about every 3 hours over an average span of about 15 hours a day. Might it be beneficial to give our bodies a bigger break?
Time-restricted feeding is “defined as fasting for periods of at least 12 hours but less than 24 hours.” This involves trying to confine calorie intake to a set window of time, typically 3–4 hours, 7–9 hours, or 10–12 hours a day, resulting in a daily fast lasting 12-21 hours. When mice are restricted to a daily feeding window, they gain less weight even when fed the exact same amount. Rodents have such high metabolisms, though, that a single day of fasting can starve away as much as 15 percent of their lean body mass. This makes it difficult to extrapolate from mouse models. You don’t know what happens in humans until you put it to the test.
The drop-out rates in time-restricted feeding trials certainly appear lower than most prolonged forms of intermittent fasting, suggesting it’s more easily tolerable. But does it work? If you have people even just stop eating between 7 p.m. and 6 a.m. for two weeks, they lose about a pound each week, compared to no time restriction. Note: no additional instructions or recommendations were given on the amount or type of food consumed; no gadgets, calorie counting, or record-keeping. They were just told to limit their food intake to the hours of 6 a.m. through 7 p.m., a simple intervention, easy to understand and implement.
The next logical step was to try putting it to the test for months instead of just weeks. Obese men and women were asked to restrict eating to the eight-hour window between 10 a.m. and 6 p.m. Twelve weeks later, they had lost seven pounds. This deceptively simple intervention may be operating from a number of different angles. People tend to eat more food later in the day, and higher-fat foods later in the day. By eliminating eating in the late evening hours, one removes prime-time snacking on the couch, a high-risk time for overeating. And indeed, during the no-eating-after-7-p.m. study, the subjects were inadvertently eating about 250 fewer calories a day. Then, there are also the chronobiological benefits of avoiding late-night eating.
I’m going to do a whole series of videos about the role our circadian rhythms have in the obesity epidemic, how the timing of meals can be critical, and how we can match meal timing to our body clocks. Just to give you a taste, the exact same number of calories at dinner is significantly more fattening than the same number of calories eaten at breakfast.
Calories in the morning cause less weight gain than the same calories given in the evening. A diet with a bigger breakfast causes more weight loss than the same exact diet with a bigger dinner. Nighttime snacks are more fattening than the same snacks in the daytime. Thanks to our circadian rhythms, metabolic slowing, hunger, carbohydrate intolerance, triglycerides, and a propensity for weight gain are all things that go bump in the night.
What about the fasting component of time-restricted feeding? There’s already the double benefit of fewer calories and avoiding night-time eating. Does the fact that you’re fasting for 11 or 16 hours a day play any role, considering the average person may only make it about 9 hours a day without eating? How would you design an experiment to test that? What if you randomized people into two groups, and forced both groups to eat the same number of calories a day and both to eat late into the evening, but with one group fasting even longer—20 hours? That’s exactly what researchers at the USDA and National Institute of Aging did.
Men and women were randomized to eat three meals a day, or to fit all those same calories into a four-hour window between 5 p.m. and 9 p.m. and fast the rest of the day. If the weight-loss benefits from the other two time-restricted feeding studies was due to the passive calorie restriction or avoidance of late night eating, then presumably both these groups should end up the same, because they’re both eating the same amount, and they’re both eating late. But that’s not what happened. After eight weeks, the time-restricted feeding group ended up with nearly five pounds less body fat. About the same number of calories, but they lost more weight. A similar study with an eight-hour window resulted in three pounds more fat loss. So, there does seem to be something to giving your body daily breaks from eating around the clock.
Because that four-hour window was at night, though, they suffered the chronobiological consequences—significant elevations in blood pressures and cholesterol levels—despite the weight loss. The best of both worlds was demonstrated in 2018: early time-restricted feeding, eating with a narrow window earlier in the day, which we’ll cover next.
Please consider volunteering to help out on the site.
- Gill S, Panda S. A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metab. 2015;22(5):789–798.
- Anton SD, Moehl K, Donahoo WT, et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring). 2018;26(2):254-268.
- Rothschild J, Hoddy KK, Jambazian P, Varady KA. Time-restricted feeding and risk of metabolic disease: a review of human and animal studies. Nutr Rev. 2014;72(5):308-18.
- Hatori M, Vollmers C, Zarrinpar A, et al. Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet. Cell Metab. 2012;15(6):848-60.
- Lai M, Chandrasekera PC, Barnard ND. You are what you eat, or are you? The challenges of translating high-fat-fed rodents to human obesity and diabetes. Nutr Diabetes. 2014;4:e135.
- Lecheminant JD, Christenson E, Bailey BW, Tucker LA. Restricting night-time eating reduces daily energy intake in healthy young men: a short-term cross-over study. Br J Nutr. 2013;110(11):2108-13.
- Gabel K, Hoddy KK, Haggerty N, et al. Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutr Healthy Aging. 2018;4(4):345-353.
- Jiang P, Turek FW. Timing of meals: when is as critical as what and how much. Am J Physiol Endocrinol Metab. 2017;312(5):E369-E380.
- Laermans J, Depoortere I. Chronobesity: role of the circadian system in the obesity epidemic. Obes Rev. 2016;17(2):108-25.
- Hutchison AT, Wittert GA, Heilbronn LK. Matching Meals to Body Clocks-Impact on Weight and Glucose Metabolism. Nutrients. 2017;9(3).
- Hirsch EHE, Halberg F, Goetz FC, et al. Body weight change during 1 week on a single daily 2000-calorie meal consumed as breakfast (B) or dinner (D). Chronobiologia 1975;2(suppl 1):31–2.
- Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring). 2013;21(12):2504-12.
- Hibi M, Masumoto A, Naito Y, et al. Nighttime snacking reduces whole body fat oxidation and increases LDL cholesterol in healthy young women. Am J Physiol Regul Integr Comp Physiol. 2013;304(2):R94-R101.
- Morris CJ, Garcia JI, Myers S, Yang JN, Trienekens N, Scheer FA. The Human Circadian System Has a Dominating Role in Causing the Morning/Evening Difference in Diet-Induced Thermogenesis. Obesity (Silver Spring). 2015;23(10):2053-8.
- Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14(1):290. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males
- Stote KS, Baer DJ, Spears K, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. 2007;85(4):981-8.
- Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018;27(6):1212-1221.e3.
Image credit: Monoar Rahman Rony via pixabay. Image has been modified.
Video includes graphics from Vecteezy.com
Motion graphics by Avocado Video
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Title
Time-Restricted Eating Put to the Test
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
Isn’t that mindblowing about the circadian rhythm stuff? Calories in the morning count less, and are healthier, than calories in the evening. So if you’re going to skip a meal to widen your daily fasting window, skip dinner instead of breakfast. I’ll get to the best-of-both worlds study next in The Benefits of Early Time-Restricted Eating.
If you missed any of the previous 12 videos in this fasting series, here they are:
- The 3,500 Calorie per Pound Rule Is Wrong
- The Reason Weight Loss Plateaus When You Diet
- The New Calories per Pound of Weight Loss Rule?
- The Benefits of Calorie Restriction for Longevity
- Potential Pitfalls of Calorie Restriction
- Benefits of Fasting for Weight Loss Put to the Test
- Is Fasting Beneficial for Weight Loss?
- Is Fasting for Weight Loss Safe?
- Alternate-Day Intermittent Fasting Put to the Test
- Is Alternate-Day Intermittent Fasting Safe?
- Does Intermittent Fasting Increase Human Life Expectancy?
- The 5:2 Diet and the Fasting-Mimicking Diet Put to the Test
If you missed my last video of the day, it’s the exciting announcement that How Not to Diet is hitting shelves on December 10. Check out the book trailer here, and you can still pre-order the book to get it right when it comes out.
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