Should You Try the Keto Diet?

By significantly reducing carbohydrate intake, the keto diet lowers insulin levels, a hormone that facilitates fat storage. This reduction promotes the mobilisation and oxidation of stored fats. Additionally, the high-fat and protein content of the diet contributes to increased satiety, reducing overall calorie intake.

The ketogenic diet is particularly renowned for its weight loss potential. Studies indicate that it can lead to greater weight loss compared to low-fat diets, particularly in the short term (Basolo et al., 2022). However, in the long-term, it seems that other diets such as low fat diets, or the Mediterranean diet offer similar weight loss benefits.

This may be partly due to the difficulty of maintaining long-term adherence to such a restrictive diet. Additionally, some of the initial weight loss may be due to water loss rather than reductions in fat mass, thus meaning that initial weight loss numbers may be inflated.

Recent evidence suggests that very low carbohydrate diets such as the keto diet are suboptimal for building muscle and strength (Margolis and Pasiakos, 2023).

When dietary carbohydrates are limited, the body looks to other fuel sources for energy, and while some of this may be from fat, emerging evidence suggests that protein may also be broken down via gluconeogenesis. This increase in protein oxidation limits availability of essential amino acids necessary for muscle protein synthesis and promotion of muscle recovery.

In other words, available protein is shifted towards energy production, meaning that the body does not have sufficient protein needed for optimal strength and hypertrophy gains. Therefore, higher protein intakes (2.3-3.1 g/kg/day) may be necessary in order to build/maintain muscle mass when implementing the keto diet.

Additionally, resistance training generally relies on stored glycogen as a primary energy source. When in ketosis, these stores are limited, thus leading to impaired performance when strength training. This is especially prevalent during higher volume training such as crossfit, bodybuilding, and strongman training.

During heavy strength training, individuals can generally manage better since other energy systems (ATP-CP) primarily contribute. When performing sets of 1-5 reps with 3-5 mins rest, this provides sufficient time for the replenishment of ATP via the ATP-CP system even when in ketosis. However, once training volume increases, carbohydrates would be required to restore the body’s energy stores once ATP-CP has been exhausted.

Regarding endurance training, the keto diet has garnered significant attention for its potential to enhance fat oxidation and provide a steady, long-lasting energy source during prolonged activities. However, the impact of the keto diet on endurance training is complex and can vary depending on individual physiology, the nature of the exercise, and the duration of diet adaptation.

The keto diet may offer benefits for endurance and conditioning by enhancing fat utilisation and reducing reliance on glycogen stores. As the body adapts to oxidising fat, athletes may experience sustained performance, particularly in ultra-endurance sports where glycogen depletion is a common challenge.

This shift can help delay or prevent “hitting the wall,” providing a steadier energy supply throughout long sessions and potentially improving focus and overall performance. Additionally, the diet’s potential to reduce body fat could further enhance endurance by lowering the energy cost of movement, making it a promising approach for athletes seeking improved body composition and stamina.

However, transitioning to a keto diet presents challenges, especially during the adaptation period, which can last several weeks. Athletes may face temporary declines in performance, fatigue, irritability, and decreased exercise capacity.

While the diet supports fat oxidation, the reduced glycogen availability may limit peak performance during high-intensity efforts or repeated sprints. Furthermore, maintaining electrolyte balance is crucial, as the diet can lead to increased electrolyte excretion, affecting muscle function and endurance. 

The “keto flu” refers to a range of symptoms that some people experience when transitioning to a keto diet, as the body shifts from using carbohydrates to fats for energy.

Common symptoms include fatigue, headaches, nausea, irritability, and muscle cramps, primarily caused by electrolyte imbalances, dehydration, and reduced glycogen stores.

These effects can be particularly challenging for those engaged in strength and conditioning training, as they may temporarily impact performance and energy levels. To manage keto flu, it is important to stay hydrated, replenish electrolytes, gradually reduce carbohydrates, increase dietary fat, adjust training intensity, and consider exogenous ketones.

These strategies can help ease the transition and support overall performance during the adaptation phase.

The keto diet can be particularly effective for short term weight loss, and may offer some benefits for endurance training and blood sugar management. However, when looking at long term data, it seems that the keto diet may not be optimal compared to other diets.

Building muscle and strength is more challenging on the keto diet, and the evidence regarding endurance training is somewhat mixed (Bailey and Hennessy, 2020). Additionally, the symptoms experienced when starting the keto diet can negatively impact adherence, as well as preventing progress with your training.

When compared to other diets, such as the Mediterranean diet which is rich in fruits, vegetables, whole grains, and healthy fats, it seems that the keto diet may not be worth it.

The Mediterranean diet is a much more balanced, sustainable, and varied diet, with well-documented long-term benefits. Additionally, this type of diet may be much more suited to a range of different types of exercise and training, due to the inclusion of more carbohydrates.

Ultimately, the best diet for you will be the one that you can adhere to for the long term, and this will vary widely between different individuals. If the keto diet is something you enjoy, and you are able to stick to the diet consistently and achieve your goals, we highly recommend that you continue with this approach.

Basolo, A., Magno, S., Santini, F. and Ceccarini, G., 2022. Ketogenic diet and weight loss: is there an effect on energy expenditure?. Nutrients, 14(9), p.1814.

Bailey, C.P. and Hennessy, E., 2020. A review of the ketogenic diet for endurance athletes: performance enhancer or placebo effect?. Journal of the International Society of Sports Nutrition, 17(1), p.33.

Margolis, L.M. and Pasiakos, S.M., 2023. Low carbohydrate availability impairs hypertrophy and anaerobic performance. Current Opinion in Clinical Nutrition & Metabolic Care, 26(4), pp.347-352.