Fasted training (fasted cardio)
Training on an empty stomach burns more fat during the session, but that does not translate into more fat lost over weeks. In a controlled trial, fasted and fed cardio produced the same fat loss on the same diet, and eating beforehand helps longer sessions. Train fasted or fed based on what you prefer; your overall calorie balance is what decides fat loss.
What the science says
- Fasted cardio burns more body fat over time Limited evidence
In a randomized trial (Schoenfeld et al., 2014), young women on a calorie deficit doing 1 hour of cardio 3 times per week lost similar weight and fat mass whether they trained fasted or after a meal, with no significant difference between groups.
- More fat used during and right after the session Moderate evidence
A meta-analysis of 46 studies (Aird et al., 2018) found fasted exercise raised circulating free fatty acids after exercise compared with fed exercise. This acute shift has not been shown to change long-term fat loss.
- Eating beforehand helps longer sessions Moderate evidence
The same meta-analysis found pre-exercise feeding improved prolonged aerobic performance (longer than about 60 minutes) but not shorter sessions.
How to apply it
Fasted training is optional. Choose the timing you can stick with and manage total food intake.
Who should be careful
People with diabetes, especially on insulin or glucose-lowering drugs, and anyone prone to low blood sugar or fainting should not train fasted without medical advice. Stop if you feel dizzy or shaky. If you have a history of eating disorders, discuss fasting practices with a professional.
Frequently asked questions
Does fasted cardio burn more fat?
Not over time. In a controlled trial, fasted and fed cardio led to the same fat loss when diet was the same.
Should I eat before a long run or ride?
Yes. Eating beforehand improved performance in sessions longer than about 60 minutes in a meta-analysis.
Is fasted training harmful?
For short sessions in healthy adults it is a matter of preference. People with diabetes or prone to low blood sugar should get medical advice first.
Scientific references
More training methods
- Drop sets Moderate evidence
A drop set takes a set to failure, then immediately cuts the load and keeps going.
- Rest-pause sets (including myo-reps) Limited evidence
Rest-pause means taking a set close to failure, resting 15–30 seconds, then squeezing out a few more reps, repeated a few times.
- Supersets Moderate evidence
A superset pairs two exercises back to back with little or no rest.
- High-intensity interval training (HIIT) Strong evidence
HIIT alternates short hard efforts with recovery.
- Zone 2 training Limited evidence
Easy, steady cardio clearly improves fitness and health, but the popular claim that "Zone 2" is a special, optimal intensity for building mitochondria and burning fat is not supported.
- Static stretching before training Limited evidence
Holding long static stretches right before lifting or sprinting slightly lowers strength and power, and it has not been shown to prevent injuries.