The other day, I came across an article in Men’s Health on the subject of intermittent fasting and exercise in the morning, which cautions against lifting weights on an empty stomach.
Here’s a snippet:
Lifting weights, sprinting, doing CrossFit WODS, and other high-intensity activities all depend on carbohydrates for fuel. If you perform any of these activities during (or worse, at the end of) your fast, your performance will suffer. Instead of getting stronger and faster, you may well get weaker and slower. If you’re a big guy with a lot of weight to lose, no big deal. Go ahead and lift on an empty stomach. You might lose a little bit of muscle, but you’ll burn fat, too—and that’s your main goal. But if you’re a slimmer guy with less muscle mass to spare, schedule your lifting workouts during your feeding window.”
Fasted lifting, it concludes, is a big mistake.
In truth, lifting weights on an empty stomach is not the catabolic, performance-sapping menace that many claim. A bout of resistance training, even when it’s done in a fasted state, will still lead to muscle being gained.
For one, your body has the ability to store plenty of carbohydrate, which can be used to fuel high-intensity activity.
Depending on how much muscle you have, your body can hold upwards of 400 grams of glycogen, which is the name given to carbohydrate stored in your muscles and liver. It’s not like you run out simply because you’re fasting.
You also need to consider when in the day you’re training.
Training on an empty stomach first thing in the morning isn’t a problem, although it can take a few weeks to get used to. When I made the switch from evening to morning training, I felt weaker and my performance did take a hit.
But over time, I got used to it.
However, the longer the fast goes on, the more likely it is that your performance will suffer. If you leave it until the afternoon or evening before you train, you won’t be able to lift as much weight or do as many reps.
Over time, this dip in strength means that the growth stimulus delivered by a given workout is going to be weaker than it otherwise would be. As a result, muscle will be gained more slowly compared to doing the same training session with a few meals inside you.
What about the claim that lifting on an empty stomach might mean losing a bit of muscle?
While training in a fasted state won’t automatically lead to the loss of muscle, it does increase the potential for muscle to be lost, depending on what time of day you train and what your overall diet looks like.
If you’re fasting all day, for example, lifting weights in the evening, then eating a big meal at night, the risk of muscle loss is certainly increased. But that’s because you’ve gone so long without eating any protein, rather than because of fasted training per se.
Bottom line? As long as the right dietary boxes are being ticked, muscle will still be gained whether you lift weights in a fasted or a fed state.
Anyway, if you want to know how to time your meals for maximum muscle growth, no matter what time of day you train, take a look at my Gutless nutrition manual. Inside, you’ll find practical, easy-to-follow strategies that can be made to fit anyone’s daily schedule, no matter how busy.
Christian Finn, M.Sc.
Founder of Muscle Evo