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Should You Train Fasted? New Research Shows It Can Hurt Strength Gains

Should You Train Fasted? New Research Shows It Can Hurt Strength Gains

New research reveals that training fasted won’t improve fat loss but can hurt your strength progress.

Written By Jim Stoppani, PhD

Updated January 22, 2025

Think training on an empty stomach gives you an edge? Think again...

A new study published in the journal Frontiers in Nutrition (2024) reveals that while fasted training might not sabotage your fat loss goals, it can hold back your strength gains.

Let’s break down what the research reveals and what it means for your workout strategy.

The Study: Fasted vs. Fed Training

Researchers examined 37 young, healthy, resistance-trained Muslim men during Ramadan—when they fast from dawn to dusk. Over an 8-week full-body weightlifting program , participants were split into two groups:

Fasted Group: Trained in the afternoon before breaking their fast.
Fed Group: Trained at night after eating.

Both groups followed the same workout program and had similar diets outside their fasting window. The researchers measured body composition, strength levels, and testosterone levels before and after the study.

Here’s what they found:

Body Fat Loss: No significant difference between groups. Both lost the same amount of body fat.
Muscle Mass: Both groups maintained lean body mass equally.
Strength Gains: The fed group saw significantly greater improvements in squat and deadlift strength compared to the fasted group.
Testosterone Levels: The fed group had higher testosterone levels, both at rest and during training, which may have contributed to their superior strength gains.

What This Means for You

If you follow an intermittent fasting (IF) protocol or train during fasting periods for personal or religious reasons, this study confirms that training while fed leads to better strength gains.

While you may not see a difference in fat loss between fed and fasted training, hitting the weights with fuel in your system can help you:

Lift heavier and progress faster on your lifts (ie, 1RM).
Maintain higher testosterone levels.
Optimize muscle recovery and growth.

In short, if strength and performance are priorities, aim to train during your eating window rather than fasted. I even recommend doing HIIT workouts in eating window.

You'll still achieve your fat-loss goals while maximizing your muscle and strength potential.

My Recommendation

As I’ve always advised, if you practice intermittent fasting , schedule your workouts during your eating window.

Whether you're trying to build muscle or get stronger, having nutrients available during training will help you perform better, recover faster, and see more progress over time.

FAQ: Training While Fasted vs. Fed

1. Will training fasted help me lose more fat?

Not necessarily. The aforementioned study found no difference in fat loss between fasted and fed training. You can achieve the same fat loss results whether you train fasted or with food in your system.

2. Does fasted training negatively affect muscle growth?

It can. While the study found both groups maintained lean mass, fasted training resulted in less strength gain, which could impact long-term muscle growth potential.

3. Why does training while fed result in better strength gains?

Eating before training provides the body with fuel for performance and supports higher testosterone levels, both of which contribute to greater strength improvements.

4. Can I still train fasted if I prefer it?

Yes, but understand that your strength gains may be limited. If fasted training fits your lifestyle better, you can still maintain lean mass and lose fat effectively.