• To meet carbohydrate (CHO) fuelling requirements, endurance athletes utilise a range of CHO options, including energy gels


• Feeding with energy gels, alongside electrolyte-containing fluids, promotes a more flexible approach to meeting fuelling and hydration demands during exercise


• Gastrointestinal (GI) problems may be present in situations with sub-optimal fluid intake and CHO gel ingestion, especially when the composition of the gel is not aligned with promoting gastric emptying


• To deliver CHO to the small intestine it is suggested the osmolality of an energy gel should be close to that of the gastric content, i.e. isotonic

Study Aims and Location

• To provide data on which energy gels are truly isotonic


• This study was completed between The University of Aberdeen and Liverpool John Moores University



• 31 product ranges from 23 brands, totalling 51 flavour variants, were assessed for nutritional composition and tonicity. All gels were marketed as Energy Gels


• Nutritional composition was taken from individual manufacturer packaging

• Gels were tested for tonicity using the water vapour method



• 1 out of 31 products tested was isotonic, osmolality in the range of 270-330 mmol/kg


• 15 % of products tested (n = 4) had an osmolality < 1000 mmol/kg


• 27 out of 31 products had an osmolality > 1000 mmol/kg



1. Despite misleading claims in the market, the Science in Sport GO Isotonic Energy Gel was the only gel on test to be truly isotonic


2. Extreme variation in exists between commercially available energy gels, impacting stomach comfort during exercise and fluid intake required to optimise CHO delivery to the small intestine


3. Not all energy gels should be considered as equals and specific energy gel choice could have implications on overall performance

4. To maximise performance and promote flexibility in fuelling, athletes should look for an energy gel that is isotonic

Zhang, X., O’Kennedy, N., & Morton, J. P. (2015). Extreme variation of nutritional composition and osmolality of commercially available carbohydrate energy gels. International journal of sport nutrition and exercise metabolism, 25(5), 504-509.