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Extremely high-fat diets or low-carb strategies are experiencing a boom in athletic circles. This also brings ketone bodies to the fore.

In the case of endurance performances, the research spent a long time focusing primarily on the energy supply and availability of carbohydrates. Later, research was done on the improvement of fat oxidation and the intake of fatty acids as an alternative energy source in order to preserve the glycogen stores.

Ketone bodies are another supplier of energy. They are produced in the body when there is an extremely restricted intake of carbohydrates (less than 50 grams of carbohydrates per day) and are used by the brain and skeletal muscles as an energy source. It is therefore little wonder that many athletes and coaches have hence derived the strategy to use ketone bodies as additional energy suppliers. And equally logical that, due to the potentially positive effects, the sports nutrition industry has discovered ketone bodies and now offers a variety of exogenous ketone body products.

Reason enough for the Swiss Sports Nutrition Society (www.ssns.ch) to scrutinise the latest research results and summarise the findings to date on the much-discussed points as follows:

• Ketone bodies in general: Whether ketone bodies can be orally ingested as an alternative energy source, is unclear.
• Carbohydrate oxidation: The discussed reduction of carbohydrate oxidation during physical exertion with a simultaneous intake of ketone bodies is unclear, as is the glycogen-savings effect. An improved replenishment of the glycogen stores is possible.
• Fat oxidation: The reduced circulation of free fatty acids possibly leads to a reduction in fat oxidation and to an improved consumption of intramuscular fatty acids.
• Recovery: Ketone bodies may possibly improve the recovery phase after a load and promote the replenishment of the glycogen stores.
• Limitations: The effect on the brain is unclear, at most, side effects in the gastrointestinal area may occur. The dosage is also unclear, and the timing has not been researched. The impact of the simultaneous intake of carbohydrates on the effect of ketone bodies has not been clarified.

Conclusion: Ketone bodies seem to possess the ability to influence our energy metabolism and the substrate consumption. Whether this effect can actually conserve glycogen under load and whether this improves athletic performance or even worsens it in the high-intensive range appears to have not yet been clarified. The sparse number of scientific studies is not meaningful enough and too small in number to recommend using ketone bodies as a supplement.

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