DDT Nation…boy oh boy do we have some awesome content for you today! Our friend and colleague, who’s an assistant professor at Texas Tech University and is doing some great research on Intermittent Fasting.
We met Grant at the annual ISSN Conference in Clearwater Florida and knew he was on to something big with his work as well as really bridging the gap with science and application.
Intermittent Fasting is a very popular nutrition method that is very effective for fat loss, great for people that have very busy schedules, and for those that prefer this type of nutrition method over others since adherence and consistency should be at the forefront for attaining results.
We wanted Grant to share his recent research findings with us and our community so we can know the correct information and how to use it the proper way within our fitness programs.
Without further ado, lets learn about why Intermittent Fasting isn’t that magical and make sure to follow Grant and his work below.
Also, make sure to checkout this awesome resource “Intermittent Fasting: A Complete Guide” HERE
-Eric and Chris
What’s Intermittent Fasting?
Most individuals who are interested in dietary trends related to physique enhancement are familiar with “intermittent fasting” or “IF.” IF is a broad term that encompasses a variety of different programs, but all IF programs employ repeated short-term fasts, typically with the goal of reducing caloric intake. For those of you who are especially interested in IF, I published a review article in Nutrition Reviews in 2015 that compared different IF regimens and their effects on body composition and basic health markers [1].
What’s Time-restricted Feeding?
One type of IF, called time-restricted feeding (TRF), is commonly practiced, but has very limited research to date. TRF simply limits all caloric intake to a given “window” of time each day. For example, 8-hour TRF is very popular and consists of consuming all calories in an 8-hour window (often something like noon to 8 P.M.). It could easily be argued that many individuals practice TRF unintentionally. Using the noon to 8 P.M. example, this simply equates to skipping breakfast and either not eating after dinner or eating something soon after dinner and then stopping. TRF typically employs the same schedule every day, but may other IF programs alternate between more restricted days with less caloric intake and less restricted days with few dietary restrictions, if any.
My Research Project: Getting Started & Methods
After seeing the limited amount of TRF research available, and because I was aware of its popularity among the general public, I was interested in conducting the first study of TRF combined with resistance training. This was during my time as a doctoral student at Baylor University. Unfortunately, I did not have funding for the project, and there was limited support for its completion. Nonetheless, I was driven to contribute to the literature in this area, and I designed and executed a preliminary research study with the goal of providing some information for future in-depth research. As a side note, I am now an Assistant Professor and thankfully have funding to pursue my research – this means that there are some more in-depth IF studies in the pipeline.
The results of this preliminary TRF and resistance training study were recently published in the European Journal of Sport Science [2]. While the full text of the article is currently located on ResearchGate, I will briefly summarize the study and give some perspectives below.
This study was a randomized controlled trial, meaning that participants were randomly assigned to the TRF group or the control group.
Both of these groups followed the same resistance training program for 8 weeks. The resistance training program consisted of 3 nonconsecutive days per week of training, and participants alternated between upper body and lower body workouts. For the upper body workout, 4 sets of 8 – 12 repetitions of barbell bench press, seated row machine, dumbbell, shoulder press, lat pulldown machine, dumbbell biceps curls, and triceps extension machine were performed. For the lower body workout, 4 sets of 8 – 12 repetitions of barbell squat/hip sled machine, lunges with dumbbells, leg curl machine, leg extension machine, and calf raise machine were performed.
Participants were instructed to reach muscular failure between 8 and 12 repetitions and to adjust the weight as necessary (set-by-set) in order to achieve this criterion. While participants were instructed how to perform all of these exercises, a limitation of this study is that we relied on workout logs and weekly text or email contact to track adherence to the program. I will say that we hounded these guys and gave them as much prodding as possible to keep them on-track. We also asked that they were completely honest with us if they missed a workout (or didn’t comply with the TRF program).
For the participants in the TRF group, unrestricted food intake was allowed on the 3 workout days each week. On the 4 non-workout days, participants were required to consume all calories within a 4-hour period. In the control group, there were no restrictions on food intake for any day. This TRF program was different than commonly practiced methods, but I wanted to experiment with allowing as much food intake as desired on workout days (to promote superior exercise performance and recovery), while using a more dramatic limitation on caloric intake on non-workout days, through the very short feeding window.
Testing was performed at the beginning of the study, after 4 weeks, and after 8 weeks. Each visit consisted of body composition assessment (DXA – dual-energy x-ray absorptiometry and ultrasound measures of the biceps brachii and rectus femoris muscles). One-repetition maximums (i.e. the most weight an individual can lift) were obtained for the leg press and bench press exercises, as well as muscular endurance measures (repetitions to failure using a percentage of the max). Dietary records were also obtained at the beginning, middle, and end of the study.
The Results
Twenty-eight participants began the study, and 18 were included in the final analysis. Of the 10 participants who weren’t included, 6 dropped out (interestingly, only one was from the TRF group!) and 4 didn’t comply with the program sufficiently (3 of these were from the TRF group). It is also important to note that these participants had not recently followed a regular resistance training program. However, most had some prior experience with weight training (often from high school athletics).
Based on some subjective measurements and interviews with our participants, most found the TRF program initially difficult, but adjusted to it after a week or two. At the end of the study, some said they would be interested in incorporating TRF as part of their lifestyle. Also, almost everyone said that the first meal after the fasting window was over was the most delicious food they had ever tasted (I can also vouch for this).
The TRF program was able to reduce calorie intake by about 650 calories per day of TRF (relative to non-fasting days in the same subjects). However, there were no group differences in body composition at the end of the study. Importantly, even though the difference wasn’t statistically significant, the members of the control group gained 2.3 kg (5 lbs) of lean mass, while the members of the TRF group had no change.
This indicated that although performing resistance training allowed individuals performing TRF to maintain muscle, muscle gain was superior in the control group (i.e. those consuming their regular diet). One very important point is that the protein intake in the groups was not identical. The TRF group consumed, on average, 1.0 grams of protein per kilogram of body weight (when both the TRF days and unrestricted days were taken into account), but the control group consumed an average of 1.4 grams per kilogram of body weight. In terms of muscle performance, both groups increased their upper and lower body strength and lower body muscular endurance.
It is important to note that this was just a preliminary study with several big limitations. However, I know that there are more in-depth projects being conducted. In fact, I am involved in a study examining TRF in amateur bodybuilders (with 5+ years consistent resistance training), which is currently under review for publication. I can’t say much about it yet, but I will say that the results were not the same as the present study.
This study also looked at various blood markers and more advanced measures than I was able to utilize in the study that was just published. Future studies using different IF programs and different populations should shed light on the potential utility of IF for physique enhancement. Additionally, future studies may need to employ a strategy like protein supplementation with IF in order to ensure optimal protein intake for physique changes.
Take-Home Points
- Time-restricted feeding is a popular form of intermittent fasting, but little research has been conducted examining its utility for physique enhancement, particularly during exercise programs.
- TRF and other forms of IF may be a good strategy to reduce calorie intake and can allow for maintenance of lean mass during a resistance training program. However, it is possible that muscular gains will not be optimal during an IF program.
- If you are considering employing IF, be sure to consume adequate protein, particularly on your fasting days.
- Based on the data in the present study, there are also large individual variations in the responses to IF. IF could be a good strategy for some, but not others. Personal preferences about eating patterns may also play a role in whether or not IF is a reasonable strategy for you to employ.
- Much more research is needed to examine the different forms of IF, particularly in combination with exercise programs.
“TRF and other forms of IF may be a good strategy to reduce calorie intake and can allow for maintenance of lean mass during a resistance training program. However, it is possible that muscular gains will not be optimal during an IF program.” – Grant Tinsley
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About Grant:
Grant Tinsley is a first-year Assistant Professor of Exercise Physiology at Texas Tech University. He earned his Ph.D. in Kinesiology and Exercise Nutrition at Baylor University, is a Certified Strength and Conditioning Specialist (CSCS), and holds degrees in physiology, nutrition, and biomedical sciences. He is an avid lifter and a voracious reader. You can learn more about Grant and access his publications from his faculty web page or his ResearchGate profile.
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References:
- Tinsley, G. M.; Bounty, P. M. L. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr. Rev. 2015, 73, 661–674.
- Tinsley, G. M.; Forsse, J. S.; Butler, N. K.; Paoli, A.; Bane, A. A.; Bounty, P. M. L.; Morgan, G. B.; Grandjean, P. W. Time-restricted feeding in young men performing resistance training: A randomized controlled trial. Eur. J. Sport Sci. 2016, 0, 1–8.
IF Resources:
IF and Lifting: Finally, a Study