Background: Intermittent fasting may be an effective tool for weight loss, but it is still unclear from previous studies to date whether it is as effective as a continuous energy restriction in terms of reducing adipose tissue and whether it leads to unwanted muscle loss. Objectives: The aim of this study was to compare the effect of intermittent fasting (IF) with continuous energy restriction (CER) on the body weight and body composition and to assess the effect of intermittent fasting also in isolation from the energy restriction. Methods: After completion of a three-week dietary intervention, differences in the weight loss and differences in the body composition were compared between three groups. The first group consumed 75% of their calculated energy intake requirements in a six-hour time window. The second group consumed 75% of their calculated energy intake requirements without a time window and the third group consumed 100% of their calculated energy intake requirements in a six-hour time window. The changes in the weight and body composition were assessed by BIA. Results: Of the 95 randomized participants, 75 completed the intervention phase of the study. The highest mean weight loss was achieved by the IF with ER (energy restriction) group (2.3 ± 1.4 kg), followed by the CER group (2.2 ± 1.1 kg); the difference between the groups did not reach statistical significance. The lowest mean weight loss was observed in the IF without ER group (1.1 ± 1.2 kg), the difference reaching statistical significance compared to the IF with ER (p=0.003) and CER (p=0.012) groups. The highest mean adipose tissue loss was observed in the CER group (1.5 ± 1.2 kg) followed by the IF with ER group (1.3 ± 1.1 kg), with no statistically significant differences between the groups. A mean adipose tissue loss was found in the IF without ER group (0.9 ± 1.1 kg) with no statistically significant differences compared to the IF with ER and CER groups. The highest mean fat-free mass loss was found in the IF with ER group (1.1 ± 1.0 kg), followed by the CER group (0.65 ± 0.91 kg) with no statistically significant differences. The IF without ER group showed the lowest mean fat-free mass loss (0.2 ± 1.3 kg), which reached statistical significance compared to the IF with ER group (p=0.027). Conclusion: The results showed a comparable effect in the weight loss and body fat reduction regardless of the timing of the food intake. The diet quality, together with the energy intake, appeared to be one of the most important factors influencing the body composition.

Department of Public Health Faculty of Medicine Masaryk University Kamenice 753 5 625 00 Brno Czech Republic

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Fruh SM. Obesity: Risk factors, complications, and strategies for sustainable long-term weight management. J Am Assoc Nurse Pract. 2017;29:S3–14. PubMed PMC

Zhao L, Dong X, Gao Y, Effects of exercise combined with diet intervention on body composition and serum biochemical markers in adolescents with obesity: a systematic review and meta-analysis. J Pediatr Endocrinol Metab JPEM. 2022. PubMed

Kessler C. Pathophysiology of Obesity. Nurs Clin North Am. 2021;56:465–78. PubMed

Howell S, Kones R. 'Calories in, calories out' and macronutrient intake: the hope, hype, and science of calories. Am J Physiol Endocrinol Metab. 2017;313:E608–12. PubMed

Enríquez Guerrero A, San Mauro Martín I, Garicano Vilar E, Camina Martín MA. Effectiveness of an intermittent fasting diet versus continuous energy restriction on anthropometric measurements, body composition and lipid profile in overweight and obese adults: a meta-analysis. Eur J Clin Nutr. 2021;75:1024–39. PubMed

Cienfuegos S, Gabel K, Kalam F. et al. Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metab. 2020;32:366–378.e3. PubMed PMC

Dong TA, Sandesara PB, Dhindsa DS. et al. Intermittent Fasting: A Heart Healthy Dietary Pattern? Am J Med. 2020;133:901–7. PubMed PMC

Ye Y-F, Zhang M-X, Lin Z, Tang L. Is Intermittent Fasting Better Than Continuous Energy Restriction for Adults with Overweight and Obesity? Diabetes Metab Syndr Obes Targets Ther. 2022. Volume 15: 2813-26. PubMed PMC

Harris L, Hamilton S, Azevedo LB. et al. Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Evid Synth. 2018;16:507–47. PubMed

Templeman I, Smith HA, Chowdhury E. et al. A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults. Sci Transl Med. 2021;13:eabd8034. PubMed

Pellegrini M, Cioffi I, Evangelista A. et al. Effects of time-restricted feeding on body weight and metabolism. A systematic review and meta-analysis. Rev Endocr Metab Disord. 2020;21:17–33. PubMed

Cioffi I, Evangelista A, Ponzo V. et al. Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: a systematic review and meta-analysis of randomized controlled trials. J Transl Med. 2018;16:371. PubMed PMC

Antoni R, Johnston KL, Collins AL, Robertson MD. Intermittent v. continuous energy restriction: differential effects on postprandial glucose and lipid metabolism following matched weight loss in overweight/obese participants. Br J Nutr. 2018;119:507–16. PubMed

Catenacci VA, Pan Z, Ostendorf D. et al. A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obes Silver Spring Md. 2016;24:1874–83. PubMed PMC

Harvie MN, Pegington M, Mattson MP. et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes 2005. 2011;35:714–27. PubMed PMC

Harvie M, Wright C, Pegington M. et al. The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women. Br J Nutr. 2013;110:1534–47. PubMed PMC

Trepanowski JF, Kroeger CM, Barnosky A. et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med. 2017;177:930–8. PubMed PMC

Hutchison AT, Liu B, Wood RE. et al. Effects of Intermittent Versus Continuous Energy Intakes on Insulin Sensitivity and Metabolic Risk in Women with Overweight. Obesity. 2019;27:50–8. PubMed

Desu MM, Raghavarao D. Sample Size Methodology. Vol. 1990. New York: Academic Press.

Fleiss JL. The Design and Analysis of Clinical Experiments. Vol. 1986. New York: John Wiley & Sons.

Forejt M, Pokorová K, Uher M, Novák J, Čermáková E. Changes in Segmental Impedances and Selected Body Composition Parameters Assessed by Multi-Frequency Bioimpedance Analysis after Fluid Consumption in Healthy Young Population. Int J Med Sci. 2023;20:1783–90. PubMed PMC

Leidy HJ, Clifton PM, Astrup A. et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;101:1320S–1329S. PubMed

Helms ER, Zinn C, Rowlands DS, Brown SR. A Systematic Review of Dietary Protein During Caloric Restriction in Resistance Trained Lean Athletes: A Case for Higher Intakes. Int J Sport Nutr Exerc Metab. 2014;24:127–38. PubMed

Longland TM, Oikawa SY, Mitchell CJ, Devries MC, Phillips SM. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016;103:738–46. PubMed

EFSA Panel on Dietetic Products, Nutrition, Allergies (NDA). Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA J. 2010;8:1462.

Weltgesundheitsorganisation FAO, EdsDiet, nutrition, and the prevention of chronic diseases: report of a WHO-FAO Expert Consultation ; [Joint WHO-FAO Expert Consultation on Diet, Nutrition, and the Prevention of Chronic Diseases, 2002, Geneva, Switzerland] Geneva: World Health Organization. 2003. (WHO technical report series)

Brázdová Z, Fiala J, Bauerová J, Hrubá D. Dietary guidelines in the Czech Republic. I.: Theoretical background and development. Cent Eur J Public Health. 2000;8:186–90. PubMed

Gupta RD, Ramachandran R, Venkatesan P, Anoop S, Joseph M, Thomas N. Indirect Calorimetry: From Bench to Bedside. Indian J Endocrinol Metab. 2017;21:594–9. PubMed PMC

EFSA Panel on Dietetic Products, Nutrition, Allergies (NDA). Scientific Opinion on Dietary Reference Values for energy. EFSA J. 2013;11:3005.

Westerterp KR. Diet induced thermogenesis. Nutr Metab. 2004;1:5. PubMed PMC

Alhamdan BA, Garcia-Alvarez A, Alzahrnai AH. et al. Alternate-day versus daily energy restriction diets: which is more effective for weight loss? A systematic review and meta-analysis. Obes Sci Pract. 2016;2:293–302. PubMed PMC

Varady KA. Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss? Obes Rev. 2011;12:e593–601. PubMed

Roman YM, Dominguez MC, Easow TM, Pasupuleti V, White CM, Hernandez AV. Effects of intermittent versus continuous dieting on weight and body composition in obese and overweight people: a systematic review and meta-analysis of randomized controlled trials. Int J Obes. 2019;43:2017–27. PubMed

Vendelbo MH, Møller AB, Christensen B. et al. Fasting Increases Human Skeletal Muscle Net Phenylalanine Release and This Is Associated with Decreased mTOR Signaling. PLoS ONE. 2014;9:e102031. PubMed PMC

Liu D, Huang Y, Huang C. et al. Calorie Restriction with or without Time-Restricted Eating in Weight Loss. N Engl J Med. 2022;386:1495–504. PubMed

Horne BD, Muhlestein JB, Lappé DL. et al. Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences. Nutr Metab Cardiovasc Dis. 2013;23:1050–7. PubMed

Nørrelund H. The metabolic role of growth hormone in humans with particular reference to fasting. Growth Horm IGF Res. 2005;15:95–122. PubMed

Soeters MR, Soeters PB, Schooneman MG, Houten SM, Romijn JA. Adaptive reciprocity of lipid and glucose metabolism in human short-term starvation. Am J Physiol-Endocrinol Metab. 2012;303:E1397–407. PubMed

Areta JL, Burke LM, Ross ML. et al. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J Physiol. 2013;591:2319–31. PubMed PMC

Mamerow MM, Mettler JA, English KL. et al. Dietary Protein Distribution Positively Influences 24-h Muscle Protein Synthesis in Healthy Adults123. J Nutr. 2014;144:876–80. PubMed PMC

Moore DR, Churchward-Venne TA, Witard O. et al. Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. J Gerontol A Biol Sci Med Sci. 2015;70:57–62. PubMed

Trommelen J, van Lieshout GAA, Nyakayiru J. et al. The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans. Cell Rep Med. 2023;4:101324. PubMed PMC

Johnston CS, Day CS, Swan PD. Postprandial Thermogenesis Is Increased 100% on a High-Protein, Low-Fat Diet versus a High-Carbohydrate, Low-Fat Diet in Healthy, Young Women. J Am Coll Nutr. 2002;21:55–61. PubMed

Efimtseva EA, Chelpanova TI. [Dietary fiber as modulators of gastrointestinal hormonal peptide secretion] Vopr Pitan. 2021;90:20–35. PubMed

Capuano E, Oliviero T, Fogliano V, Pellegrini N. Role of the food matrix and digestion on calculation of the actual energy content of food. Nutr Rev. 2018;76:274–89. PubMed

Poti JM, Mendez MA, Ng SW, Popkin BM. Is the degree of food processing and convenience linked with the nutritional quality of foods purchased by US households? Am J Clin Nutr. 2015;101:1251–62. PubMed PMC

Zou ML, Moughan PJ, Awati A, Livesey G. Accuracy of the Atwater factors and related food energy conversion factors with low-fat, high-fiber diets when energy intake is reduced spontaneously. Am J Clin Nutr. 2007;86:1649–56. PubMed

Bolanowski M, Nilsson BE. Assessment of human body composition using dual-energy x-ray absorptiometry and bioelectrical impedance analysis. Med Sci Monit Int Med J Exp Clin Res. 2001;7:1029–33. PubMed

McLester CN, Nickerson BS, Kliszczewicz BM, McLester JR. Reliability and Agreement of Various InBody Body Composition Analyzers as Compared to Dual-Energy X-Ray Absorptiometry in Healthy Men and Women. J Clin Densitom Off J Int Soc Clin Densitom. 2020;23:443–50. PubMed

Kfir A, Lahav Y, Gepner Y. Cross-Validation of a New General Population Resting Metabolic Rate Prediction Equation Based on Body Composition. Nutrients. 2023;15:805. PubMed PMC

Heymsfield SB, Thomas DM, Bosy-Westphal A, Müller MJ. The Anatomy of Resting Energy Expenditure: Body Composition Mechanisms. Eur J Clin Nutr. 2019;73:166–71. PubMed PMC

Olejníčková J, Forejt M, Čermáková E, Hudcová L. Factors influencing basal metabolism of Czechs of working age from South Moravia. Cent Eur J Public Health. 2019;27:135–40. PubMed