The Ketogenic 'Keto' Diet has crept back into the spotlight this year.
It is a very low carbohydrate high fat (LCHF) and moderate protein diet which aims to induce ketosis in the body. Ketosis is a metabolic state where the body has switched to using ketone bodies (a by-product of fat degradation) as an energy source, rather than glucose from our glycogen stores.
On this diet. fat contributes 75-80% of daily energy requirements, protein 15-20% and carbohydrates less than 50g/day. That amount of carbohydrates is equivalent to about 2 slices of bread! During high intensity endurance exercise, the body is traditionally reliant on internal glycogen stores from carbohydrate loading and external food top ups. Following the Keto Diet is thought to spare the glycogen stores and rely on burning fat for energy during endurance exercise.
Research done at the Australian Institute of Sport compared athletes on this diet, with one that was high in carbohydrates; and another that periodised carbohydrate intakes according to exercise intensity. Results showed there was no improvement in performance for those following a keto diet compared with a high carb, or a periodised carbohydrate approach. In fact, instead of sparing glycogen for the latter stages of endurance exercise, increased burning of fat actually impaired the body's capacity to use carbohydrates. Whilst fat can be utilised at low intensities over a long period, it does not provide energy to the body quick enough to allow for a burst in acceleration that is characteristic of endurance sport.
In other words, following a Keto Diet may not beneficial for endurance athletes looking to improve performance. Instead of following one strict way of eating, whether high fat or high carb, athletes should match their food intake to their training program.
