What Does Science Say: Restricted Intermittent Fasting & Athletic Performance



A few weeks ago, we took a look into the branches of different types of intermittent fasting (IF). Today, we are going to take a closer look at one of those types, time-restricted feeding (TRF), and its effects on athletic performance.

TRF may be used as a form of IF that increases compliance compared to other forms of IF. TRF entails a schedule with a set time frame (3-4 h, 7-9 h, or 10-12 h) in which individuals may consume ad libitum energy intake (as desired) [1].

An example of this would be a daily schedule in which you consume all of your food for the day in an 8-hour timeframe, such as from 12pm-8pm. The 16 hours in between until the next day would be your fasting period, in which there is no caloric intake.

If you make good choices on the foods you choose to consume, TRF could help you reduce your daily caloric intake and potentially put you in a caloric deficit.

One study supports that practicing a time-restricted feeding schedule in which all caloric consumption regularly occurs within a daily time frame of 12 hours or less results in several cardiometabolic benefits. It can also improve sleep and inhibit excessive weight gain [2].  

Moreover, TRF can have a positive influence on immune cells by preventing the onset of age-related differences in red blood cell and hematocrit levels, without having a negative impact on muscular performance and strength [3].

Practicing diets with reduced caloric intake alone can work as quick weight-loss strategies, but can ultimately result in both fat and muscle mass reductions. Incorporating exercise into your routine along with TRF may yield more positive results on your health and body composition [4].

One study followed 2 groups of healthy males throughout 8 weeks of resistance training. Both groups had equal energy intake, but followed different feeding schedules. One group followed an alternating day schedule of late TRF (1pm-9pm), while the second group was unrestricted and ate between 8am-9pm. At the end of the 8 weeks, both groups had increased muscle mass, but only the TRF group additionally achieved a decrease in total body mass, fat mass, and reductions in certain biomarker levels (i.e. blood glucose, insulin, triglycerides). Fat-free mass was maintained and increases in maximal strength did not differ between the 2 groups [5].

Another study that involved a TRF regimen (~7.5 hour feeding window) combined with resistance training in female participants found that there was no impairment in fat-free mass gains or muscular performance compared to the group that had no time restrictions and consumed energy intake over ~13 hours of the day. Maximal strength and muscular endurance increased among both groups without any significant differences [6].


While, additional research exploring the effects of time-restricted feeding on active populations and different age groups would be beneficial, the existing evidence provides promising support that one can follow a TRF schedule and work out without the concerns of hindering physical gains and performance, while gaining the additional health benefits that come with TRF.


References


1. Rothschild J, et al. Time‐restricted feeding and risk of metabolic disease: a review of human and animal studies. Nutr Rev. 2014; 72(5): 308–18. doi:10.1111/nure.12104

2. Melkani GC, Satchidananda P. Time‐restricted feeding for prevention and treatment of cardiometabolic disorders. J Physiol. 2017; 595(12): 3691–700. doi:10.1113/JP273094

3. Gasmi M, et al. Time-restricted feeding influences immune responses without compromising muscle performance in older men. Nutr. 2018; 51-52: 29-37. doi:10.1016/j.nut.2017.12.014

4. Parr EB, Heilbronn LK, Hawley JA. A time to eat and a time to exercise. Exerc Sport Sci Rev. 2020;48(1):4-10. doi:10.1249/JES.0000000000000207


5. Moro T, et al. 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. J Transl Med. 2016; 14(1): 290. doi:10.1186/s12967-016-1044-0


6. Tinsley GM, et al. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr. 2019; 110(3): 628-40. doi:10.1093/ajcn/nqz126







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