Does fasted training work?

Fasted training refers to working-out on an empty stomach, typically in the morning before eating. The theory is that exercising in a fasted state can teach the body to burn more stored fat for energy because glycogen stores are lower. However, the research is mixed.

In order to understand the pros and cons, let’s examine the various claims of fasted training:

Fasting is good for weight loss

The theory is that working-out while fasted should enhance your ability to burn fat and increase the amount of fat you burn. This would meet the key goal in cycling: less fat mass and hence a higher power-to-weight ratio. There are potentially benefits of fasted exercise including improved glucose tolerance and insulin sensitivity, increased mitochondrial adaptations, and exercise-induced ketone production.

This might be OK for a short, low-intensity session but we typically need to replenish glycogen stores (from food) after exercising for about 60-90 minutes.

One study conducted in 2014 on 20 healthy female participants found that fasted exercise was no better than fed exercise for reducing body weight and total fat mass during a diet designed for weight loss. The workouts were 1 hour at moderate intensity.

Another study conducted in 2013 on overweight females examined the effects of fasted training on high-intensity exercise. Again, there were no differences between the groups: both groups reduced body fat, but no superior effects of fasted exercise were observed.

Fasted training improves performance

Since it was established in the 1950s that fuelling exercise improves performance, there is little chance that fasted exercise will aid performance.

A recent meta study from 2018 examined all the recent studies comparing fed vs. fasted exercise and concluded there was no benefit.

Fasted training improves your ability to burn fat

This is probably the strongest argument for fasted training. The theory is that with reduces blood glucose, the body will be forced to turn to fat stores and thus those pathways will be enhanced.

However once again, the studies don’t support the theory. Whilst some metabolic markers were different across study groups, no improvement in metabolism could be demonstrated.

It should also be said that any attempt to improve fast metabolism runs the risk of compromising your ability to burn carbohydrates. This is a particular risk for female athletes who are naturally better fat-burners than men.


We already know that performance is not enhanced by starving the body of fuel. Also, whilst there remains a lack of long-term studies, the benefits of fasted exercise aren’t definitively proven.

What matters most for weight loss and for fitness gains is the overall balance of calories consumed versus those expended and the consistency of your workout regime.

The best approach is one that you can maintain consistently and that aligns with your body’s needs and preferences. Some people perform better with a small meal or snack before and during exercise, whilst others feel fine working out on an empty stomach. It’s essential to listen to your body and find what works best for you.

If you really want to try fasted training for yourself, I’d suggest limiting it to low to moderate intensity exercise of less than 1 hour. Any longer (or harder) than that and you’re likely to reduce the effectiveness of the training.

If you want any advice about your training why not book a FREE consultation with inSync Cycling Coach?