Females using diet breaks did not lose more fat than females following continuous dieting. The two groups had no differences in muscle mass, weight loss, or hunger ratings. Women using diet breaks had higher levels of impulse control (i.e., less likely to binge) than the continuous dieting group.


SUMMARY OF DIET BREAK VS CONTINUOUS DIETING STUDY

  • Females using diet breaks did not lose more fat than females following continuous dieting.

  • The two groups had no differences in muscle mass, weight loss, or hunger ratings.

  • Women using diet breaks had higher levels of impulse control (i.e., less likely to binge) than the continuous dieting group.


WHAT IS A DIET BREAK

Do an internet search for diet breaks. Articles will often discuss the benefits of diet breaks for maintaining muscle and metabolic rate, better satiety control, and greater fat loss compared to continuous dieting. Many people say they use diet breaks to reset their metabolism from continuous dieting.

HOW LONG SHOULD YOU TAKE OFF FROM DIETING?

A diet break is just like it sounds: a temporary increase in calories while dieting. A diet break does not mean you get to eat what you want! You stay on your diet, but instead of being in a calorie deficit or calorie restriction, you raise your calorie levels to maintenance.

Maintenance calories are the number of calories you need to maintain weight. Most people will take a diet break every 2 weeks, but others will use a one-week diet break. Implementing a diet break is designed to provide psychological relief from the stress of dieting while also reportedly increasing metabolic rate and reducing muscle mass loss.

BENEFICIAL IN SOME STUDIES

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.

A 2018 study called 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 fat loss compared to a continuous diet group. There was a smaller reduction in resting metabolic rate in the group that cycled their calories. (Byrne et al., 2018)

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). (Campbell et al., 2020)

NOT SO BENEFICIAL IN SOME STUDIES

Contrary to these initial beneficial findings with the initial studies, several studies were published that found no benefit of diet breaks. For example, the ICECAP study was a one-week diet break (i.e., spaced every three weeks) that resulted in a lower hunger than continuous dieting for 12 weeks.

The diet break group also had a 2 fold lower dropout rate than the continuous diet group. (However, the 1-week diet break had similar changes in lean mass, fat mass, and RMR compared to the continuous dieting group. (Peos et al., 2021)

In another study, 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.

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.

Both groups lost weight and body fat similarly and maintained lean muscle, with no significant differences between the groups. The diet break group also had lower hunger and desire to eat than the continuous diet group. (Siedler et al., 2020)

how long should a diet break be diet break to reset metabolism diet break

Both groups lost weight and body fat similarly and maintained lean muscle, with no significant differences between the groups.

NEW STUDY ON ON RESISTANCE-TRAINED FEMALES

A new study was just published, which may be a nail in the coffin for the so-called benefits of diet breaks. Researchers had women follow a diet in conjunction with resistance exercise; they were either assigned to a continuous diet group or a diet break group. Both groups had a 25% reduction in calories.

The diet break group had an increase in calories to maintenance calories (i.e., calories to maintain body weight) after the second and fourth weeks of dieting. The continuous dieting group dieted for six weeks, but since the diet break group had an increase in calories twice, they dieted for 8 weeks, so both groups were in a calorie deficit for 6 weeks.

how long should a diet break be diet break to reset metabolism diet break

Both groups received a high-protein diet (1.8g/kg/bw or .8 grams per pound of bw). Carbohydrates were 60% and fat 40% of the diet.

NO DIFFERENCES IN FAT LOSS, MUSCLE MASS, OR METABOLIC RATE

At the end of the study, both groups lost weight and body fat while maintaining muscle. There were no differences between the diet break and continuous dieting groups for weight, fat loss, metabolic rate, muscle, satiety, or hunger scores. The researchers did find that the diet break group had a lower disinhibition score.  (Siedler et al., 2023)

 

how long should a diet break be diet break to reset metabolism diet break

Disinhibition measures how a person responds to tempting foods from an environmental response. For example, limiting yourself to 1 slice of cake while dieting. A higher disinhibition score means you are more likely to overeat when an emotional or environmental situation occurs.

This means the diet break group had higher restrain levels. This study was only six weeks, so this can provide beneficial psychological effects while dieting over a longer time. The MATADOR study was a 32-week dieting study, and the ICECAP study was 16 weeks.

A series of studies on diet breaks are not showing any beneficial effects on losing weight or metabolic rate, fat loss, or muscle. Still, it does seem that long-term diet breaks, which involve cutting calories and raising calories to maintenance levels, can provide substantial psychological benefits with more restraint.

REFERENCES

Byrne, N. M., Sainsbury, A., King, N. A., Hills, A. P., & Wood, R. E. (2018). Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes (Lond), 42(2), 129-138. https://doi.org/10.1038/ijo.2017.206

Campbell, B. I., Aguilar, D., Colenso-Semple, L. M., Hartke, K., Fleming, A. R., Fox, C. D., Longstrom, J. M., Rogers, G. E., Mathas, D. B., Wong, V., Ford, S., & Gorman, J. (2020). 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), 19. https://www.mdpi.com/2411-5142/5/1/19

Peos, J. J., Helms, E. R., Fournier, P. A., Ong, J., Hall, C., Krieger, J., & Sainsbury, A. (2021). Continuous versus Intermittent Dieting for Fat Loss and Fat-Free Mass Retention in Resistance-trained Adults: The ICECAP Trial. Med Sci Sports Exerc, 53(8), 1685-1698. https://doi.org/10.1249/mss.0000000000002636

Siedler, M., Lewis, M., Trexler, E., Lamadrid, P., Waddell, B., Bishop, S., SanFilippo, G., Callahan, K., Mathas, D., Mastrofini, G., Henselmans, M., Vårvik, F., & Campbell, B. (2023). The Effects of Intermittent Diet Breaks during 25% Energy Restriction on Body Composition and Resting Metabolic Rate in Resistance-Trained Females: A Randomized Controlled Trial. Journal of Human Kinetics, 86, 117-132. https://doi.org/10.5114/jhk/159960

Siedler, M. R., Trexler, E. T., Humphries, M. N., Lamadrid, P., Waddell, B., Ford, S., SanFilippo, G., Callahan, K., Gegenheimer, J., Reyes, J., Pane, O., Klahr, D., Espinal, M., Urrutia, M., & Campbell, B. I. (2020). Correction to: The effect of moderate intermittent versus continuous energy restriction on body composition and resting metabolic rate in resistance-trained females: A randomized controlled trial. Journal of the International Society of Sports Nutrition, 17(1), 67-67. https://doi.org/10.1186/s12970-020-00402-4

 

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