Intermittent fasting (IF) has been a hot topic lately. It is a diet strategy in which you are to consume your total days’ worth of food in a specified window of time. Depending on who you talk to, the duration of that window and when it starts can vary. One of the more popular windows is 16 hours of fasting with 8 hours of eating, typically beginning around 10:00am and ending at 6:00pm like this recent study used. This tends to result in skipping breakfast and avoiding late night eating close to bed. The results of this new study shows some possible effects of IF and why some people may find success with it.

Moro, T., Tinsley, G., Longo, G. et al. Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial. J Int Soc Sports Nutr 17, 65 (2020). https://doi.org/10.1186/s12970-020-00396-z
 
 

Who & What

Sixteen elite cyclists under the age of 23 were randomly split into two groups with different time windows of eating 3 meals and 1 snack:
1. IF group: 8-hr window; 10:00am to 6:00pm
2. Regular group: 14-hr window; 7:00am to 9:00pm
Both groups consumed all of the calories and nutrients they needed within these time windows while continuing to train the same amount. They did this for a total of 4 weeks.

How Did They Do?

Weight: Despite being coached to eat enough to maintain their weight, the IF group lost weight while keeping their muscle and the regular group saw no changes. The lost weight for the IF group may be due to avoiding late night snacks and eating more in line with their body’s natural clock. What I mean by this is during the day the body is used to being awake, active and needing to produce energy which you provide it by eating. Later in the evening the body is getting ready to sleep and slow down so it’s not trying to produce a lot of energy. If eating a lot right before bed, your body will have a tougher time using all of that energy because you’re less active and this could result in weight gain over time. There is also a lot of time in between meals for the regular group which could cause them to be hungrier and unintentionally eat a little more.
 
Muscle and Inflammation: Even though neither group saw any changes in muscle during the 4 weeks, there was a drop in muscle building hormones in the IF group. This decrease may be because the group wasn’t eating enough and losing weight. Building muscle requires energy and if it’s not being provided you can’t expect to build much muscle. What was more interesting is that the IF group had less inflammation than the regular group. It’s hard to read too much into this as we don’t know how much fruit & vegetables or how much sleep each group was getting but this could be worth keeping an eye on.
 
Performance – The Big Test: There was no difference in performance between the groups. Short, sweet and to the point.

Key Take Aways

  • – You don’t have to follow an IF diet if looking to improve performance
  • -Always make sure that you are timing your meals/snacks around your training to optimally fuel before, during and after to get the most of your sessions
  • – If having a snack before bed, make sure it is higher in protein as this will better help with muscle building and recovery
  • – Eat fruit & vegetables regularly to keep inflammation down and help your body recover
  • – Go to bed! Get around 7-10 hours of sleep each night
 
There is not one single diet that can work for everyone and IF may work for some people but not for others. For most athletes though I advise against IF to make sure that optimal fueling before and after training occurs in order to perform and recover their best. If you are curious about what you should be eating to meet your goals, feel free to schedule a call with me and we can get you started seeing results.