Im sure you have heard of someone trying intermittent fasting.
Can it work for fat loss?
Is it healthy?
How does it work?
What is the best protocol?
Intermittent fasting is a popular diet that seems to be getting even more popular.
However, with any popular diet protocol there are some myths surrounding it, but there also may be some truths.
In this article I am going to dive into the latest research on Intermittent fasting when it comes to body composition and exercise. I also go over how we would set up an IF diet for a online client.
If you would rather listen to my discussion with one of the leading researchers when it comes to intermittent fasting when it comes to fat loss and exercise then listen to this podcast here.
What is intermittent fasting?
Intermittent fasting can be defined as a feeding window, and a fasting window. During the fasting window there are no calorie-containing items consumed, and it can range from hours to days. During the feeding period this is when all of your calories are consumed.
The typical protocols are:
- Alternate day fasting: This is where someone will eat one day and then not eat another day.
- Modified alternate day fasting: This is where someone goes 24 continuous hours without eating. The plus side to this one is that you can eat everyday, albeit some days will be very low calorie.
- Periodic fasting: This is more than 24 hours of continuous fasting.
- Time restricted feeding: This is the one that most people hear about for fat loss. This is where there are designated windows to eat and not to eat throughout the day. For example, 16 hours fasting and then 8 hours feeding (16/8), there is also 20/4, and 18/6.
According to Matthew Stratton there are higher adherence rates and less disruption to daily life following a time restricted feeding protocol compared to an alternate day fast, or whole day fast.
My favorite quote from Matthew Stratton is “Intermittent Fasting tells us when to eat, not what to eat.”
What this means is that you can stack any other fad diet on top of this one and do it in combination, because intermittent fasting just tells you what times to eat throughout the day.
So yes you can do a keto intermittent fasting diet, because again IF tells us WHEN to eat, not WHAT to eat.
But as you will find out there are some things you do need to pay attention when following an IF approach.
The big upside to an intermittent fasting protocol is that it can help someone decrease their overall energy intake throughout the day. As Matthew Stratton puts it, it “tricks” people into eating less.
By telling people to restrict their feeding times, the research shows that they reduce their caloric intake by around 20%.
In multiple studies done on IF, the research shows that subsequent food intake does NOT make up for the decrease in energy intake during the fasting protocol (Tinsley et al., 2017, Stote et al., 2007). In their 2002 paper Johnstone et al., found that subjects only increased their energy intake in the first meal following the fast.
In the podcast episode Stratton says that people only increase their caloric intake in the first uncontrolled meal and then the rest of the meals they go back to normal.
Another study Stratton brings up is Moro et al. (2016). In this study they had subjects who had at least 5 years of weight training experience. They had a fasting group and regular eating group and they aimed to get everyone to eat the same amount of protein/calories etc.
They found no difference in muscle mass, BUT the IF group lost weight while the regular group did not. The IF group consumed less calories overall. This study showed that restricting times when the subjects could eat made it tougher for subjects to eat the same amount as the regular eating group, therefore getting them into a calorie deficit.
All of the studies done so far showed that the people who eat less lost more weight, and then people who ate more gained or maintained weight.
What this tells us is that there is NO special fat loss benefit to intermittent fasting, other than it is a tool in the toolbox to help you eat less calories and can be a viable strategy to help someone get into a calorie deficit.
Stratton mentions that it can be useful for someone who doesn’t want to track calories but wants to lean out or lose weight.
In terms of strength and performance IF doesn’t seem to hamper performance (Tinsley et al., 2017). Stratton mentions that all of the studies done on strength and performance have had the subjects train DURING their feeding window. Another important aspect is that all of the studies have had the subjects eat high protein.
Stratton also mentions that he would not recommend IF to someone who is trying to maximize muscle growth. It may be a viable strategy for someone who doesn’t have a lot of training experience, but at some point they probably will have a tough time building more muscle following an IF approach. The biggest reason is that the more muscle you have, the tougher it is to build muscle without being in a calorie surplus. For some, a calorie surplus can be upwards of 3,000 to 4,000 calories per day, imagine eating all of those calories in a small time frame.
There are some downsides to this approach:
Not eating for hours could make adherence very challenging, especially if an event comes up during the fasting window.
While studies show that energy intake does NOT increase at later meals, some people may have problems with overeating or might not be able to tolerate the hunger that could come with not eating for hours.
To sum all of this up IF is a GREAT tool in the toolbox for those looking to lose weight/fat, and there are no performance decrements so long as the training is within the feeding window and you consume enough protein.
However it probably isnt great for building muscle, especially if you have already put on a good amount of muscle.
Lastly, there are some potential downsides that you must be aware of such as increased hunger/cravings.
If meals are too spread out and hunger is an issue during fat loss it could be helpful to reduce hunger.
Here is how we would set up an IF diet for an online client:
- Remember its just a tool in the toolbox.
- If hunger is an issue with regular eating patterns because your meals are too spread out, then doing IF may be beneficial to reduce hunger.
- Start with a more conservative window. Start with something like 14 hours fasting, 10 hours eating and then work your way up. Don’t go straight into long fasting windows.
- You probably don’t need to do more than 18 hours of fasting per day, as the research saw very little to no benefit of going from a 6 hour feeding window to a 4 hour feeding window.
- Stick with a time restricted feeding protocol because this allows for more flexibility in case events come up. You probably do NOT want to be the weirdo not eating.
- Make sure you consume an adequate amount of protein. Aim for around .8 to 1g per lb of bodyweight per day. This helps with building/maintenance of muscle, but it also helps with satiety and does a great job of managing your caloric intake.
- Your first meal after a fast should probably be higher in nutrient dense foods like lean protein and fiber. Since you will probably be hungry, highly palatable foods following fast could cause you to overeat.
- Train DURING your feeding window OR if you train in the fasted window, make sure you consume protein as soon as possible following your workout.
If you need help setting up an IF protocol or have more questions on this topic, fill out the link here.
Tinsley, G. M., Forsse, J. S., Butler, N. K., Paoli, A., Bane, A. A., La Bounty, P. M., Morgan, G. B., & Grandjean, P. W. (2017). Time-restricted feeding in young men performing resistance training: A randomized controlled trial. European journal of sport science, 17(2), 200–207. https://doi.org/10.1080/17461391.2016.1223173
Stote, K. S., Baer, D. J., Spears, K., Paul, D. R., Harris, G. K., Rumpler, W. V., Strycula, P., Najjar, S. S., Ferrucci, L., Ingram, D. K., Longo, D. L., & Mattson, M. P. (2007). A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. The American journal of clinical nutrition, 85(4), 981–988. https://doi.org/10.1093/ajcn/85.4.981
Johnstone, A. M., Faber, P., Gibney, E. R., Elia, M., Horgan, G., Golden, B. E., & Stubbs, R. J. (2002). Effect of an acute fast on energy compensation and feeding behaviour in lean men and women. International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity, 26(12), 1623–1628. https://doi.org/10.1038/sj.ijo.0802151
Stratton, M. T., Tinsley, G. M., Alesi, M. G., Hester, G. M., Olmos, A. A., Serafini, P. R., Modjeski, A. S., Mangine, G. T., King, K., Savage, S. N., Webb, A. T., & VanDusseldorp, T. A. (2020). Four Weeks of Time-Restricted Feeding Combined with Resistance Training Does Not Differentially Influence Measures of Body Composition, Muscle Performance, Resting Energy Expenditure, and Blood Biomarkers. Nutrients, 12(4), 1126. https://doi.org/10.3390/nu12041126
Moro, T., Tinsley, G., Bianco, A., Marcolin, G., Pacelli, Q. F., Battaglia, G., Palma, A., Gentil, P., Neri, M., & Paoli, A. (2016). 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. Journal of translational medicine, 14(1), 290. https://doi.org/10.1186/s12967-016-1044-0