In a variety of sports, athletes often seek to lose weight while keeping muscle for a competitive advantage. For example, these can include athletes in any form of fitness competition, bodybuilding, or even combat sports like wrestling or judo.
The problems of athletes who attempt to diet is that, as they restrict food calories, most of the time they also risk losing muscle and hindering their performance.
But through use of a special dietary protocol developed by sport scientists from the Olympic Training Center in Barcelona, new research suggests that athletes can succeed in keeping muscle and improving their performance through a calorie restriction program that was achieved through every-other-day bouts of intermittent partial fasting (1).
“After six weeks of participating in a caloric restriction program based on intermittent partial fasting, athletes’ physical performance was enhanced,” the researchers wrote in the Journal of the International Society of Sports Nutrition (1). The athletes lost a modest amount of weight by the end of the study, primarily related to a significant, 15 percent reduction in body fat. Despite the modest weight loss, the athletes’ lean body mass was only reduced by less than 3 percent.
They also saw significant improvement in physical performance parameters. These included lower heart rate, lactate levels, and fatigue perception. By the end of the study, in fact, the athletes improved their energy expenditure while running by 10 percent.
Essentially, these results show that the fasting intervention promoted a more efficient use of energy when carrying out physical activity. The authors theorized these improvements could be explained by improved efficiency of mitochondria, the energy-producing structures inside cells (2).
Combining Higher Protein with Intermittent Fasting
The study included 12 healthy male athletes who trained between three and six times per week. The participants reduced energy intake by 30 to 40 percent with respect to their usual diet by alternating three fasting days with four normal eating days per week for six weeks.On average, the participants consumed 77 grams of protein per day or approximately 1 gram of protein per kilogram bodyweight. While the scientists did observe minor decreases in lean body mass, they noted that this reduction “could probably be avoided by increasing protein intake to around 2.3 grams per kilogram of body weight or by supplementing the diet with branched-chain amino acids that maintain lean mass while promoting the loss of fat mass.”
Increasing protein intake for athletes is a well-established method to offset muscle loss during times of caloric restriction, and may offer another component to maintaining or improving performance during fasting (3). In two separate performance studies that involved Isagenix products, for example, men and women consuming 2 grams of protein per kilogram body weight, including quality protein from Isagenix products, saw significant improvements in muscular performance (4, 5).
The researchers also noted that the intervention significantly reduced the athletes’ daily vitamin and mineral intake, leading to values lower than recommended dietary allowances for athletes. This reduction was most apparent for iron, niacin, riboflavin, pyridoxine, and vitamins A and D. If maintained over a longer period, low vitamin and mineral intake could compromise athletic performance. To prevent micronutrient deficiency, the researchers suggested that including vitamin and minerals supplements should be considered.
The study also suggests that athletes could find similar performance benefits when employing Isagenix-style Cleanse Days. These could also be combined with a modified protocol on Shake Days with high-protein IsaLean Pro Shakes, appropriate calorie intake to fuel performance, and supplementation with Complete Essentials Daily Pack to avoid micronutrient deficiencies.
- Pons V, Riera J, Capo X et al. Calorie restriction regime enhances physical performance of trained athletes. J Int Soc Sports Nutr. Mar 2018; 15(12). [Epub]
- López-Lluch G, Hunt N, Jones B et al. Calorie restriction induces mitochondrial biogenesis and bioenergetic efficiency. Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1768-73.
- Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010 Feb;42(2):326-37.
- Arciero PJ, Ives SJ, Norton C et al. Protein-Pacing and Multi-Component Exercise Training Improves Physical Performance Outcomes in Exercise-Trained Women: The PRISE 3 Study. Nutrients. 2016 Jun 1;8(6). pii: E332.
- Ives SJ, Norton C, Miller V et al. Multi-modal exercise training and protein-pacing enhances physical performance adaptations independent of growth hormone and BDNF but may be dependent on IGF-1 in exercise-trained men. Growth Horm IGF Res. 2017 Feb; 32:60-70.