FASTING FOR WEIGHT LOSS: GOOD OR BAD FOR GAINING MUSCLE

Intermittent fasting (IF) has recently gained popularity in the fitness community as a method for weight loss and fat loss while improving health. IF is not a diet; it is a time-restricted method (periods in which you don’t eat), not a calories-restricted eating plan. During fasting, numerous benefits can occur, such as increased growth hormone secretion, improved metabolic health, and decreased heart rate and blood pressure.

The most popular IF protocol is the 16/8 Method (aka Leangains fast for 16 hours). In this method, a 16-hour fast is required. You have an 8-hour eating window. For example, you could eat between 12 pm and 8 pm and then fast from 8 pm to 12 pm the next day.

The idea behind fasting is that it can help reduce calorie intake, increase fat mobilization, and improve insulin sensitivity, leading to weight loss. (Bachman et al., 2016; Edinburgh et al., 2019) However, fasting also has its drawbacks if you want to build muscle.

Fasting can lead to impaired muscle gains from reduced protein synthesis and reduced exercise performance, leading to reduced long-term muscle gains. (Stannard & Thompson, 2008)­(Clayton & James, 2016; Slater et al., 2023) This article will explore the pros and cons of fasting for fat loss and muscle hypertrophy and the nutritional strategies to minimize muscle loss while fasting.

INTERMITTENT FASTING BENEFITS

Increased Fat Mobilization and Improved Insulin Sensitivity: Fasting impacts metabolism by promoting ketogenesis, enabling the body to burn stored fat instead of glucose for energy. (Dohm et al., 1986; Halberg et al., 2005; Slater et al., 2023)

Fasting and insulin sensitivity has been well studied. A study published in Cell Metabolism showed that early time-restricted feeding, a type of intermittent fasting, improved insulin sensitivity, blood pressure, and oxidative stress in men with prediabetes, even without weight loss. (Sutton et al., 2018)

IF has been shown to improve insulin sensitivity, but the effects are similar to those consuming a calorically restricted diet. (Horne et al., 2020) The effects of IF on insulin sensitivity may vary depending on the intermittent fasting strategy, such as the length of fasting, individual health status, and lifestyle factors.

INTERMITTENT FASTING FOR ATHLETES AND WEIGHT LOSS

IF helps reduce calorie intake by limiting the time when individuals consume food. IF can lead to a calorie deficit, essential for weight loss. (McIver et al., 2019) Studies have demonstrated weight loss ranging from 0.8% to 13% of baseline weight, with no serious adverse events. (Welton et al., 2020)

It should be mentioned that several large-scale studies have found that when calories are similar, there are no differences in weight loss between IF and calorie-restricted diets. (Lowe et al., 2020; Zhao et al., 2023) The advantages of IF are that most people don’t count calories and can lose weight easily by eating within certain periods.

INTERMITTENT FASTING DRAWBACKS

Fasting and muscle hypertrophy is an intense debate among researchers and scientists. Going for several hours without food can lead to reductions in protein synthesis. In an article titled A Muscle-Centric Perspective on Intermittent Fasting: A Suboptimal Dietary Strategy for Supporting Muscle Protein Remodeling and Muscle Mass? Williamson and Moore argue that IF may not be an optimal dietary strategy for supporting muscle mass because of the negative impact on protein synthesis.

Williamson and Moore argue that intermittent fasting may not be the most effective dietary strategy for optimizing muscle protein remodeling and muscle mass due to its potential negative effects on muscle protein synthesis. They emphasize the importance of adequate protein intake and proper timing of protein consumption to maximize muscle protein synthesis and promote muscle growth. (Williamson & Moore, 2021)

FASTING AND MUSCLE GROWTH

it is important to note that intermittent fasting may not preserve lean mass any more than continuous calorie-restricted diets and may even lead to a decrease in lean mass. (Clifton, 2017; Harris et al., 2018) However, it is important to note that the effect of intermittent fasting on muscle loss may depend on the duration and type of intermittent fasting. (Korkut, 2022)

FASTING FOR WEIGHT LOSS AND RESISTANCE TRAINING

Resistance exercise is a powerful tool to preserve muscle while dieting. Two recent studies looking at IF combined with resistance exercise found minimal negative effects on muscle loss. (Moro et al., 2016; Tinsley et al., 2017). However, the long-term effect is not known. For example, the study by Moro et al. found a decrease in testosterone and IGF-1 at 8 weeks in the IF group, which may negatively affect performance in the long term. (Moro et al., 2016)

Therefore, based on the provided research results, intermittent fasting may increase fat mobilization during exercise but also negatively affect lean mass. Muscle loss may be dependent on the duration of the fast.

FASTING FOR WEIGHT LOSS  AND EXERCISE PERFORMANCE

In general, many studies have found that skipping breakfast can lead to a reduction in exercise performance. (Clayton & James, 2016) A 2023 study found that fasting before an evening sprint cycle test resulted in a 3.8% decrease in performance. (Slater et al., 2023) Multiple studies have found that IF can reduce sprint times. (Aziz et al., 2017; Cherif et al., 2017) Other studies have found that fasting worsened endurance athletes’ cycling performance time. (Gleeson et al., 1988)

STRATEGIES TO PREVENT MUSCLE LOSS WHILE IF

To prevent muscle loss while intermittent fasting, there are several strategies that you can follow on your fasting days that can prevent muscle loss.

1.)   EAT ENOUGH PROTEIN: Firstly, ensuring adequate protein intake is maintained during the feeding periods is important. Protein is essential for muscle growth and repair, and a lack of protein can lead to muscle loss. Therefore, it is recommended to consume high-quality protein sources such as lean meats, fish, eggs, and dairy products during feeding.

2.)   LIFT WEIGHTS: Resistance training can be incorporated into the exercise routine to help maintain muscle mass. Resistance training effectively prevents muscle loss during weight loss and caloric restriction. Therefore, incorporating resistance training into the exercise routine during the feeding periods can help maintain muscle mass while intermittent fasting.

3.)   DON’T FAST FOR LONG PERIODS: Thirdly, ensuring that the intermittent fasting protocol is appropriate for the individual is important. The duration and type of intermittent fasting may affect the potential for muscle loss. Longer fasts (i.e., 24-hour fasts) will make you more susceptible to muscle loss.

FASTING FOR WEIGHT LOSS CONCLUSION

Many fasting methods for fitness vary in the amount of time fasting, which can range from several hours to days. IF can be an effective tool for fat loss due to its ability to increase fat mobilization and reduce calorie intake. However, its potential negative effects on exercise performance and muscle hypertrophy should be considered by those looking to optimize their fitness goals.

While there are studies on intermittent fasting and its effects on muscle mass, most of the research is short-term, and the long-term effects of intermittent fasting on muscle loss remain largely unknown. One study by Kim et al. (2021) suggests that concerns have been raised about the side effects of long-term intermittent fasting, including muscle loss, ketosis, and electrolyte imbalance. (Kim et al., 2021)

Before implementing it into their lifestyle, individuals must weigh the pros and cons of intermittent fasting for weight loss and their unique objectives and circumstances. Given that weight loss and fat loss are the same with IF and calorie-restricted diets, but protein synthesis, muscle hypertrophy, and performance can be affected by fasting, it makes sense to determine if losing muscle is worth the risk of IF.

REFERENCES

Aziz, A. R., Che Muhamad, A. M., Roslan, S. R., Ghulam Mohamed, N., Singh, R., & Chia, M. Y. H. (2017). Poorer Intermittent Sprints Performance in Ramadan-Fasted Muslim Footballers despite Controlling for Pre-Exercise Dietary Intake, Sleep, and Training Load. Sports (Basel), 5(1). https://doi.org/10.3390/sports5010004

Bachman, J. L., Deitrick, R. W., & Hillman, A. R. (2016). Exercising in the Fasted State Reduced 24-Hour Energy Intake in Active Male Adults. Journal of Nutrition and Metabolism, 2016, 1984198. https://doi.org/10.1155/2016/1984198

Cherif, A., Meeusen, R., Farooq, A., Ryu, J., Fenneni, M. A., Nikolovski, Z., Elshafie, S., Chamari, K., & Roelands, B. (2017). Three Days of Intermittent Fasting: Repeated-Sprint Performance Decreased by Vertical-Stiffness Impairment. Int J Sports Physiol Perform, 12(3), 287-294. https://doi.org/10.1123/ijspp.2016-0125

Clayton, D. J., & James, L. J. (2016). The effect of breakfast on appetite regulation, energy balance and exercise performance. Proceedings of the Nutrition Society, 75(3), 319-327. https://doi.org/10.1017/S0029665115004243

Clifton, P. (2017). Assessing the evidence for weight loss strategies in people with and without type 2 diabetes. World J Diabetes, 8(10), 440-454. https://doi.org/10.4239/wjd.v8.i10.440

Dohm, G. L., Beeker, R. T., Israel, R. G., & Tapscott, E. B. (1986). Metabolic responses to exercise after fasting. Journal of Applied Physiology, 61(4), 1363-1368. https://doi.org/10.1152/jappl.1986.61.4.1363

Edinburgh, R. M., Hengist, A., Smith, H. A., Travers, R. L., Betts, J. A., Thompson, D., Walhin, J.-P., Wallis, G. A., Hamilton, D. L., Stevenson, E. J., Tipton, K. D., & Gonzalez, J. T. (2019). Skipping Breakfast Before Exercise Creates a More Negative 24-hour Energy Balance: A Randomized Controlled Trial in Healthy Physically Active Young Men. The Journal of Nutrition, 149(8), 1326-1334. https://doi.org/https://doi.org/10.1093/jn/nxz018

REFERENCES

Gleeson, M., Greenhaff, P. L., & Maughan, R. J. (1988). Influence of a 24 h fast on high intensity cycle exercise performance in man. Eur J Appl Physiol Occup Physiol, 57(6), 653-659. https://doi.org/10.1007/bf01075984

Halberg, N., Henriksen, M., Söderhamn, N., Stallknecht, B., Ploug, T., Schjerling, P., & Dela, F. (2005). Effect of intermittent fasting and refeeding on insulin action in healthy men. J Appl Physiol (1985), 99(6), 2128-2136. https://doi.org/10.1152/japplphysiol.00683.2005

Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., Whittaker, V., Sharp, T., Lean, M., Hankey, C., & Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Evidence Synthesis, 16(2), 507-547. https://doi.org/10.11124/jbisrir-2016-003248

Horne, B. D., Grajower, M. M., & Anderson, J. L. (2020). Limited Evidence for the Health Effects and Safety of Intermittent Fasting Among Patients With Type 2 Diabetes. JAMA, 324(4), 341-342. https://doi.org/10.1001/jama.2020.3908

Kim, B. H., Joo, Y., Kim, M. S., Choe, H. K., Tong, Q., & Kwon, O. (2021). Effects of Intermittent Fasting on the Circulating Levels and Circadian Rhythms of Hormones. Endocrinol Metab (Seoul), 36(4), 745-756. https://doi.org/10.3803/EnM.2021.405

REFERENCES

Korkut, B. (2022). The effects of intermittent fasting on nighttime blood pressure levels. 39(3), 793-797. https://doi.org/10.52142/omujecm.39.3.38

Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., Philip, E., Vittinghoff, E., Heymsfield, S. B., Olgin, J. E., Shepherd, J. A., & Weiss, E. J. (2020). Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Internal Medicine, 180(11), 1491-1499. https://doi.org/10.1001/jamainternmed.2020.4153

McIver, V. J., Mattin, L. R., Evans, G. H., & Yau, A. M. W. (2019). Diurnal influences of fasted and non-fasted brisk walking on gastric emptying rate, metabolic responses, and appetite in healthy males. Appetite, 143, 104411. https://doi.org/https://doi.org/10.1016/j.appet.2019.104411

Moro, T., Tinsley, G., Bianco, A., Marcolin, G., Pacelli, Q. F., Battaglia, G., Palma, A., Gentil, P., Neri, M., & Paoli, A. (2016). 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. Journal of Translational Medicine, 14(1), 290. https://doi.org/10.1186/s12967-016-1044-0

Slater, T., Mode, W. J. A., Pinkney, M. G., Hough, J., James, R. M., Sale, C., James, L. J., & Clayton, D. J. (2023). Fasting Before Evening Exercise Reduces Net Energy Intake and Increases Fat Oxidation, but Impairs Performance in Healthy Males and Females. Int J Sport Nutr Exerc Metab, 33(1), 11-22. https://doi.org/10.1123/ijsnem.2022-0132

Stannard, S. R., & Thompson, M. W. (2008). The effect of participation in Ramadan on substrate selection during submaximal cycling exercise. J Sci Med Sport, 11(5), 510-517. https://doi.org/10.1016/j.jsams.2007.03.003

REFERENCES

Sutton, E. F., Beyl, R., Early, K. S., Cefalu, W. T., Ravussin, E., & Peterson, C. M. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism, 27(6), 1212-1221.e1213. https://doi.org/https://doi.org/10.1016/j.cmet.2018.04.010

Tinsley, G. M., Forsse, J. S., Butler, N. K., Paoli, A., Bane, A. A., La Bounty, P. M., Morgan, G. B., & Grandjean, P. W. (2017). Time-restricted feeding in young men performing resistance training: A randomized controlled trial. Eur J Sport Sci, 17(2), 200-207. https://doi.org/10.1080/17461391.2016.1223173

Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss: Systematic review. Can Fam Physician, 66(2), 117-125.

Williamson, E., & Moore, D. R. (2021). A Muscle-Centric Perspective on Intermittent Fasting: A Suboptimal Dietary Strategy for Supporting Muscle Protein Remodeling and Muscle Mass? Front Nutr, 8, 640621. https://doi.org/10.3389/fnut.2021.640621

Zhao, D., Guallar, E., Woolf, T. B., Martin, L., Lehmann, H., Coughlin, J., Holzhauer, K., Goheer, A. A., McTigue, K. M., Lent, M. R., Hawkins, M., Clark, J. M., & Bennett, W. L. (2023). Association of Eating and Sleeping Intervals With Weight Change Over Time: The Daily24 Cohort. Journal of the American Heart Association, 12(3), e026484. https://doi.org/doi:10.1161/JAHA.122.026484