Training while fasting: yes, but it depends
Walking, easy jogging or yoga are fine. For hard or long sessions, eating first is better.
What studies show
A review of 46 studies found that for aerobic exercise under an hour, training fasted does not hurt performance. For longer efforts, eating beforehand usually performs better. You burn a bit more fat during a fasted session, but that does not translate into more fat loss over the weeks.
How much to move
The World Health Organization recommends 150 to 300 minutes per week of moderate activity (or 75 to 150 vigorous) plus strength training on at least 2 days. Regular movement matters more than timing.
Practical tips
- If you train hard, place the session near your eating window.
- Drink water and, in long fasts or hot weather, some salt.
- If you feel dizzy, stop and eat something.
Sources
- Aird TP, Davies RW, Carson BP. Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: a systematic review and meta-analysis. Scand J Med Sci Sports. 2018;28(5):1476-1493.
- Bull FC et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54:1451-1462.
General information; not a substitute for a health professional.