“Fitness has helped me discover so much about myself and the things I can achieve.” - Ryan Speedo Green

Fasted workouts is always one of the biggest questions I get and honestly, something I bring up with all my athletes or active clients.

I am guessing we can all think of a rule we read in some magazine somewhere or a personal trainer drilled into your head about what you should be doing or what is best in this area. Am I right?!

First things first we need to define what “fasted” means. This is when the body goes without food or calories for a minimum of 8 hours, though some define it as 10-14 hours of no calorie intake.

There are a lot of research studies out there on this topic. Overall, fasted workouts under 60 minutes do support weight loss. However, it also shows a loss in both lean muscle and fat mass. And anything over one hour of training in a fasted state shows limited performance and too much muscle breakdown.

In a 2020 review of existing research on this topic concluded that the evidence is not there to support that fasted workouts support increased fat loss and overall endurance athletes should avoid high-intensity training. Additionally, it showed increases in adrenaline and cortisol and lowered insulin (typically not great to see this, though it can be personally dependent). In one study the weight lost during fasted workout was not attributed to the fasted workout but rather to the lower calorie intake in general due to fasting and overall the fasted workout also lowered physical performance.

As I mentioned, there are a lot of other studies out there as well. But I tried to pick a couple of the better ones and read about things as objectively as I could.

My takeaways are:

It’s ok to do a fasted workout IF:
- it’s under 60 mintues
- lower intensity
- you have tried eating before a workout and get digestive distress
- You are committed to eating a real and balanced meal in less than 30 minutes post workout
It’s better to NOT fast if:
- you are working out over 60 minutes
- you have performance goals, not just a weight loss goal
- you get tired or hungry when training

In general, there are other nutritionists and sports dietitians that say the research supports fasted workouts increasing fat burning during exercise but not to a greater fat loss overall.

What I see is that while we can debate the weight loss around fasted workouts, what we can not ignore is the decreased performance. 99% of all professional and competitive athletes do not do fasted workouts. If that' doesn’t say it all, I don’t know what would!

For this reason for about 90% of my clients, I encourage eating at least a little something prior to working out.