Fasted Exercise For Fat Loss

The subject of fasted exercise for fat loss continues to be a controversial one. Proponents of the technique suggest that performing low intensity exercise on an empty stomach will increase utilisation of stored fat rather than recently ingested carbohydrate. Indeed, this is the preferred strategy of many bodybuilding enthusiasts.

 However, whilst fuel is a key component of the body's response to exercise, it is certainly not the only one, with hormonal activity and enzyme secretion, amongst other factors, all affecting fat burn during exercise. Whilst previous studies have shown increased breakdown of fatty acids in fasted individuals performing long duration, low intensity cardio (>90 minutes) no difference has been found between fasted and non-fasted individuals performing moderate intensity exercise (1).

 Fasting does, however, pose a risk to energy output and reduced performance under this intensity. Research shows that fuel type plays a more significant role in fat oxidisation, with low GI foods such as legumes supporting greater endurance running capacity than high GI alternatives such as potatoes.

 The take home advice, therefore, is to consume a meal roughly 2-3 hours prior to training, or a smaller one around 30 minutes out (depending on personal preference) unless your workout will be long, slow work of more than 90 minutes duration (ideally first thing in the morning, with breakfast to follow straight after).

  (1) Schoenfeld, B. Does cardio after an overnight fast maximize fat loss? Strength and Conditioning Journal, 33: 23–25, 2011.