Using refeeds has been proposed to increase leptin and stimulate metabolic rate. It has long been assumed that a cheat day can stimulate metabolic rate. A single cheat day will likely have a minimal meaningful effect on metabolic rate and likely be counterproductive for fat loss. A refeed must be at least two to three days in a row to have a meaningful effect.
ARE DIET BREAKS & REFEEDS GOING TO PREVENT LOSS OF MUSCLE?
- Based on the research, diet break and refeeds do not restore metabolism or RMR.
- Refeeds do provide a psychological benefit from dieting and may improve performance.
- It is doubtful that refeeds preserve lean mass based on the studies of Pesos et al. (4)
9/29 DO DIET BREAKS PREVENT METABOLIC ADAPTATION AND LOSS OF LEAN MUSCLE?
Diet breaks or refeeds are the talk of the fitness industry to prevent metabolism from dropping and losing muscle mass while dieting. A diet break is just what it sounds like; it’s taking a break from a calorie deficit and raising your calories to maintenance levels for a week or two.
Dieting for extended periods of time has been shown to result in suppressed metabolism, loss of lean muscle mass, increased hunger, and a plateau in weight loss. There has been much debate about the efficacy of diet breaks for preventing metabolic adaptation, as some research has shown beneficial effects while others have shown no effect.
Researchers took resistance-trained females (i.e., 20 years old) with normal body fat (i.e., 25% body fat at baseline) and randomized them to two groups: continuous dieting and a diet break group. The subjects were instructed to reduce their caloric intake by 25% for 6 weeks during the study. The baseline calories for both groups were roughly 1,700 calories, and while dieting, both groups reduced calories to 1,250-1,375 calories.
Both groups dieted for six weeks, but the diet break group took a seven-day break (i.e., raised their calories to maintenance levels) every two weeks. The continuous diet break group dieted straight for six weeks. Besides their calorie restriction, the subjects consumed roughly .8 grams of protein per pound of body weight. The remaining calories were distributed at 60% from carbohydrates and 40% from dietary fat. Both groups performed resistance training 3 days per week with an alternating upper body/lower body split.
The total training volume was equal between the continuous diet and diet break groups. Researchers measured body composition before and after the study. They also measured subjective measures of hunger, irritability, etc., which are common while dieting.
Results
Both groups lost weight and body fat similarly and maintained lean muscle, with no significant differences between the groups. The diet break group unexpectedly had a slight loss of lean muscle mass, whereas the continuous dieting group had a slight gain in muscle. This was not statistically significant, so don’t emphasize this much because of individual differences during the study. Both groups maintained their metabolic rates during the study, and no metabolic adaptation occurred, as so many people commonly expect.
The diet break group also had lower hunger and desire to eat than the continuous diet group. This can result in greater diet adherence over an extended period with sustained fat loss. The great news about this study is that you can raise your calories and lose the same amount of fat!
Diet breaks, when used with resistance training, result in similar fat loss to continuous dieting with the added benefit of less hunger, lower desire to eat, and less susceptibility to overeat when in the presence of highly palatable foods or stressful situations.(8)
Several studies have found that increasing carbohydrates to maintenance levels or baseline calories during a diet can preserve lean muscle mass.
DIET BREAK STUDIES
· The MATADOR study found that when subjects reduced their calories for two weeks (~33% reduction in energy intake) and then increased their calories to maintenance levels resulted in weight loss without a loss of lean mass and had fat loss compared to a continuous diet group. (2) There was a small reduction in RMR in the group that cycled their calories.
· Campbell et al. reported that 5 days of calorie restriction (35% reduction Monday-Friday) with 2 days of refeeds day back to maintenance (i.e., Saturday and Sunday) resulted in greater retention of lean mass and RMR compared to continuous calorie restriction (~25% caloric deficit, seven days a week). The macronutrient ratio on the refeeds days was 43% carbohydrates, 22% protein, and 35% fat. (3)
DIET BREAK STUDIES-CONT.
· In a series of studies by Pesos et al., a one-week diet break (i.e., spaced every three weeks) resulted in a lower hunger and greater sensation of hunger than continuous dieting for 12 weeks. The diet break group also had a 2 fold lower dropout rate than the continuous diet group. (4) While the 1-week diet break had no change in lean mass, fat mass, or RMR compared to the continuous dieting group, the diet break group had greater muscular endurance. (5)
It can be suspected that refeeds can be useful to pull back if one is getting too lean before a competition or peaking too early. It should be mentioned that a refeed should be kept at maintenance levels as an increase in calories will lead to an increase in body fat. In an excellent review article on refeeds, the authors hypothesized a more frequent refeed as an athlete becomes leaner.
For example, a 4:1 ratio (Caloric Restriction: Refeed) at the beginning of prep, moving to a 3:1 ratio, then a 2:1 ratio, and finally a 1:1 ratio to preserve lean mass and enhance fat loss. (6) There are no downsides to a refeed as it can reduce hunger, improve mood, and exercise performance as long as the refeeds stay within a caloric balance of the person’s prescribed diet. Whether refeeds increase RMR or preserve lean mass during a diet remains to be determined, but refeeds seem to provide psychological relief that may be beneficial during weight loss.
3 PHASES OF WEIGHT LOSS
In an excellent review paper by Heymsfield et al., an in-depth review of the physiological responses to weight loss has been discussed. (6) The phases of weight are loss are broken down into three distinct phases:
Phase 1 (5% Weight Loss): Rapid weight loss, slow rate of fat loss, loss of muscle because of glycogen, water, and electrolytes.
Phase 2 (~5 to 20-25% Weight Loss): More gradual weight loss, acceleration of fat loss, and a gradual plateau in lean mass loss accompanied. These outcomes are heavily determined by the amount of caloric deficit, exercise, macronutrient composition, gender, etc.
Phase 3 Famine and Starvation (~20 – 50% (until death): Rapid weight loss, rapid acceleration of fat mass, loss of muscle mass.
DIET BREAK STUDIES KEY POINTS:
- Based on the research, refeeds/diet breaks do not restore metabolism or RMR.
- Refeeds do provide a psychological benefit from dieting and may improve performance.
- It is doubtful that refeeds preserve lean mass based on the studies of Pesos et al. (4)
REFERENCES:
3. Bill I. Campbell, Danielle Aguilar, Lauren M. Colenso-Semple, and others, ‘Intermittent Energy Restriction Attenuates the Loss of Fat Free Mass in Resistance Trained Individuals. A Randomized Controlled Trial’, Journal of Functional Morphology and Kinesiology, 5.1 (2020), 19 <https://doi.org/10.3390/jfmk5010019>.
4. Jackson J. Peos, Eric R. Helms, Paul A. Fournier, Julian Ong, and others, ‘Continuous versus Intermittent Dieting for Fat Loss and Fat-Free Mass Retention in Resistance-Trained Adults: The ICECAP Trial’, Medicine and Science in Sports and Exercise, 53.8 (2021), 1685–98 <https://doi.org/10.1249/MSS.0000000000002636>.
5. Jackson J. Peos, Eric R. Helms, Paul A. Fournier, James Krieger, and others, ‘A 1-Week Diet Break Improves Muscle Endurance during an Intermittent Dieting Regime in Adult Athletes: A Pre-Specified Secondary Analysis of the ICECAP Trial’, PloS One, 16.2 (2021), e0247292 <https://doi.org/10.1371/journal.pone.0247292>.
6. Guillermo Escalante, Bill Campbell, and Layne Norton, ‘Effectiveness of Diet Refeeds and Diet Breaks as a Precontest Strategy’, Strength and Conditioning Journal, Publish Ahead of Print (2020), 1 <https://doi.org/10.1519/SSC.0000000000000546>.
7. S. B. Heymsfield and others, ‘Voluntary Weight Loss: Systematic Review of Early Phase Body Composition Changes’, Obesity Reviews: An Official Journal of the International Association for the Study of Obesity, 12.5 (2011), e348-361 <https://doi.org/10.1111/j.1467-789X.2010.00767.x>.
About The Author
