Over the years meal frequency has been a topic of interest when it comes to nutritional strategies to enhance body composition. To this day you may still hear people say “you need to eat 6-8 meals a day to build muscle”. Along with this claim, benefits of an increased metabolism were proposed. Thankfully due to advancements in the scientific literature, the claim has been largely discredited that consuming frequent meals will increase ones metabolic rate1. In more recent years there seems to be more of a shift towards various fasting protocols and their touted benefits.
What is Intermittent Fasting –
Intermittent Fasting, or as its term more commonly used in the scientific literature (time-restricted feeding), is the concept of only consuming food during a certain block of time, typically between 4-8 hours. This nutritional strategy has evidence supporting its use for increasing satiety and reduces ones overall caloric intake for the day2. However, with all of these benefits, some concerns still exist. Muscle Protein Synthesis is stimulated by protein consumption and the scientific literature has suggested that MPS cannot be stimulated again for 3 or more hours after being spiked3. In theory, this would devalue intermittent fasting as one would be limited to how frequently they spike MPS in their short meal window. Although, a recent study has been released that may show otherwise.
The Study –
This study took female athletes and assessed body composition, fat mass, fat free mass, muscle thickness of the biceps and quadriceps4. Markers of performance were also being monitored such as vertical jump and squat. Lastly questioners were given to the participants to examine how well the diet was tolerated. Some of the participants were also given HMB (β-hydroxy β-methylbutyrate) which is a dietary supplement that is a metabolite of the amino acid Leucine. HMB has been shown to have a positive anabolic effect when it comes to new lifters, or those coming back from a long hiatus5.
There were three groups within the study. The first group was the control that had no restricted time period feeding and was given a placebo in place of the HMB. A second group was doing time-restricted feeding (an 8-hour block), along with an HMB placebo. And finally, the third group was doing time-restricted feeding with HMB on top of that. This was an 8-week study in which all three groups did supervised resistance training. The participants were training three times per week and were alternating between upper and lower body training.
In the time-restricted group, participants would have their first meal around noon then would have to finish their last meal around 8 pm (8-hour feeding window). The participants were all female and between the ages of 18-30. The participants had also all been resistance training for at least 2 years prior to beginning the study. The study started with 40 participants, and by the end of the study there was complete data on 24 out of the 40 participants.
Participants in the study were not provided their exact caloric intake. However, they were given a caloric goal to hit (the goal placed the participants in a very slight caloric deficit to try and elicit a little bit or muscle gain and fat loss). An interesting fact about the study is all participants were given access to protein powder since the researchers wanted to ensure each participant got in at least 1.4g/kg of protein a day. Participants were given food logs and a food scale. During the end of the study it was examined that the participants average around 1.6g/kg protein a day.
Importance of Protein –
The protein in this study was important due to the findings of a previous study by the researchers. Previously, a very similar study was conducted by the researchers where instead of females; all male athletes were put through a very similar time-restricted protocol6. Within this previous study, the male athletes were given only a 4-hour feeding window, and protein was not monitored. The findings of that study were not so favorable, leading the authors to try and recreate the study in females correcting some of the previous issues such as low dietary protein intake and short feeding window.
Results from the participants questioners indicated that time restricted feeding were very well subjectively tolerated. Results of the study indicated no differences between the groups when it came to muscle hypertrophy and performance markers.
Things to Note –
The participants in this study had an 8-hour feeding window. This is quite a large time frame for meals. If you were to eat every 2 hours, you could have 4 meals. When most people think of intermittent fasting I assume they picture eating one meal a day and losing a ton of weight. While eating one meal a day may make you lose weight, you definitely won’t be in an optimal position to build lean body mass. The larger eating window is important to consider for those considering intermittent fasting.
Along with a larger feeding window, the protein was also kept quite high. This was an important difference between this study and the last. Keeping your protein high is critical in building and preserving your lean mass as shown by this study.
The training protocol in this study was done in a fed state. What that means is the participants had eaten before their training. This is important for performance while exercising. If participants were to have trained while still fasting, we may have seen slightly different results.
Take Home Message –
Intermittent Fasting can be an effective tool in ones reservoir when It comes to fat loss, not because it inherently increases your metabolic rate, but because it will most likely increase your satiety and therefore you may eat less. What this study basically summarized was those participating in intermittent fasting, if protein is accounted for, training stimulus is done in a fed state, and feeding window is at least 8-hours, they can expect to still make positive lean body mass gains.
1. La Bounty PM, Campbell BI, Wilson J, Galvan E, Berardi J, Kleiner SM, et al. International Society of Sports Nutrition position stand: meal frequency. J Int Soc Sports Nutr. 2011 Mar 16;8:4.
2. Tinsley GM, Forsse JS, Butler NK, Paoli A, Bane AA, La Bounty PM, et al. Time-restricted feeding in young men performing resistance training: A randomized controlled trial. Eur J Sport Sci. 2017 Mar;17(2):200–7.
3. Mitchell WK, Phillips BE, Hill I, Greenhaff P, Lund JN, Williams JP, et al. Human skeletal muscle is refractory to the anabolic effects of leucine during the postprandial muscle-full period in older men. Clin Sci Lond Engl 1979. 2017 Oct 27;131(21):2643–53.
4. Tinsley GM, Moore ML, Graybeal AJ, Paoli A, Kim Y, Gonzales JU, et al. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr. 2019; ePub ahead of print.
5. Correia, A.L.M., et al., Pre-exercise beta-hydroxy-beta-methylbutyrate free-acid supplementation improves work capacity recovery: a randomized, double-blinded, placebo-controlled study. Appl Physiol Nutr Metab, 2018.
6. Moro T, et al. Effects of eight weeks of time-restricted feeding on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Journal of Translation Medicine. 2016:14:219.
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