Intermittent fasting in the last few years has been all the rage. And amongst all the hype is the much debated is the tendency of people falling into fasted training.
Fasting does have some benefits around blood sugar management and teaching you to distinguish true hunger cues, but strength training in a fasted state may not be the best way to build muscle and could have some potentially harmful affects. Here’s why you probably want to fuel before a strength-training session in order to get the most out of your hard work.
How Your Body Uses Food When You Train
To fully understand why fasting and strength training don’t mix, it’s important to brush up on some biology. When you eat a pre-workout meal or snack, your body breaks down this food to fuel your workout: Your body stores carbohydrates as glycogen in its muscles, which it then uses for energy when you lift.
But when you don’t have any fuel in the tank, your body fatigues quickly and you may not reap all the strength-building benefits of your training. And that’s exactly what you ‌don’t‌ want when your goal is building strength and muscle.
1. You’ll Probably Fatigue Faster
As you may already know, progressive overload is the key to building strength and muscle. Essentially, this is where you gradually increase your training volume (either your sets, reps or weight) in order to get stronger. But consistently making your workouts more challenging demands quite a bit of energy. Without the proper fuel, you may not have any extra resources to use. Strength training while fasted can lead to quicker fatigue with your glycogen depleted. And when you can’t push as hard, lifting more weight or more reps can feel infinitely more difficult.
Not to mention, your brain may not feel as sharp as usual. Low blood sugar can cause your brain to feel fatigued, foggy or irritable, according to the Mayo Clinic. Not exactly ideal when you’re in need of a distraction-free workout.
2. You May Lose Muscle
Your muscles need energy (glycogen) in order to exercise. That’s why your body stores about three-quarters of your total glycogen in your muscles. Your muscle glycogen goes down with intense exercise, and the tougher your workout, the more quickly you deplete your glycogen stores. And these stores aren’t restored until you eat a meal with carbohydrates.
When you don’t have enough glycogen stored in your muscles, your body needs to rely on other sources of energy, especially muscle muscle tissue which is easy for your body to use as energy.
3. You May Not Gain Strength
Muscle is difficult to build and you need to be in a calorie surplus in order to gain strength. In other words, you need to be eating more calories than you burn.
Also, as mentioned above, you need to constantly increase the challenge of your workouts in order to gain strength. If you’re not able to do that ‌and‌ you’re in a calorie deficit, your body’s ability to build muscle is hindered.
So, if building muscle and getting stronger is your goal, fasting probably isn’t the best way to do it.
4. You Put Yourself at Risk of Injury
This can’t be said enough: Strength training with progressive overload is tough. Chances are, the last few reps of each set will feel pretty challenging, which is where proper form is especially important. When you’re lifting a heavier weight than before, you’re at higher risk of injury. If you’re already low on energy, lifting to fatigue becomes riskier because your form could break down.
Bottom Line
Although strength training in a fasted state isn’t exactly dangerous, it probably won’t help you get the muscle-building results you’re seeking — and may even put you at risk of injury.
If you don’t love eating a huge meal before training, even a little carb based pre-workout snack like rice cakes or a banana can fuel your workout, giving you enough energy to make the most of your training session.
