A keto diet is generally defined as a high-fat, moderate-protein and very-low-carbohydrate diet, consisting of 75 per cent fat, 25 per cent protein and 5 per cent carbohydrates. It was first used as a medical, nutritional therapy to control epilepsy, but over the years, it showed a difference in body composition by reducing weight and body-fat percentage and has been increasingly used in this regard.
- A ketogenic diet has shown to reduce weight by causing a reduction in fat-free mass and lipid synthesis and increase in lipolysis and fat metabolism,
- Being on ketosis leads to low insulin levels and promotes fat oxidation by allowing fats to move from the cell to the circulation. This process of breaking down fats to provide energy leads to a state called ketosis, which happens in 3–4 days,
- With a keto diet, there is an increased ability to preserve glycogen stores from depleting during exercise.
Incorporating 75 per cent fat in your diet can be a challenge due to its high percentage. To sustain ketosis, include more saturated fats such as butter, bacon, olive oil, fatty fish, pumpkin seeds, sunflower seeds, cheese, cream cheese, etc. Keep protein intake at moderate levels as high levels of protein can convert to glucose, interfere with ketone production, and alter ketosis. Include slow-digesting carbs that are majorly fibre-rich to reduce calories and not cause a glucose spike.
Insulin levels are also another important factor to be considered in the keto diet. Insulin stores glucose in muscle or fat cells and prevents fat metabolism (fat moving out of the cell). Being on ketosis leads to low insulin levels and promotes fat oxidation by allowing fats to move from the cell to the circulation. This process of breaking down fats to provide energy leads to a state called ketosis, which happens in 3–4 days.
Once the glucose stores get depleted, there is a possibility of getting keto flu as the body starts fighting back as a natural response due to low glucose. This may leave you feeling less energetic and lethargic. However, it is important to be keto-adapted to obtain the physical benefits, which take about 3–5 weeks or more. Being keto-adapted means your body has now efficiently started to use fats and ketones as the major fuel source for the muscle and the brain—ketones can move across the blood-brain barrier, similar to glucose.
As an athlete, carbohydrates are the predominant source of fuel used. It is important to understand the various energy sources used in an activity. Muscle glycogen and intramuscular glycogen are the major fuel sources utilised during high-intensity, short-duration activity. However, the human body is able to metabolically shift and efficiently utilise fat as an energy source during low-intensity long-duration activity.
Most evidence found that the cause of fatigue and decreased athletic performance is due to the depletion of muscle glycogen stores and the impaired metabolic shift to utilize fat stores. With a keto diet, there is an increased ability to preserve glycogen stores from depleting during exercise. It also stimulates the release, transport, uptake and utilization of fat in the muscle to convert as energy. However, it takes 3–5 weeks to adapt to the diet, and there might be a possibility of having keto fever, as mentioned earlier.
As previously mentioned, a ketogenic diet has been shown to reduce weight by causing a reduction in fat-free mass and lipid synthesis and increasing lipolysis and fat metabolism. This can be used for athletes looking to cut down weight. However, this was observed along with a 10 per cent of calorie restriction. A keto diet has also been shown to maintain muscle mass as it reduces gluconeogenesis during ketosis and preserves muscle mass, causing a muscle-sparing effect. There is still no positive observation in terms of gaining muscle mass.
Maintaining proper hydration on a keto diet as more loss of fluid and electrolytes is observed due to low insulin levels. Insulin allows the kidneys to store sodium, and sodium is filtered out of the body with low insulin. There are also increased levels of uric acid. To reduce sodium imbalance and uric acid build-up, maintain functions of tissues, reduce the risk of keto flu, and improve performance, it is necessary to consume enough fluids. Sodium can be included by consuming salty nuts or adding more salt to your meals. Potassium, present in avocado, and magnesium, found in pumpkin seeds can also be supplemented.
More research is required on how a keto diet impacts athletic performance. However, it has been observed that high-fat diets do not improve exercise performance at high intensities as much, as they lower muscle glycogen stores by 50 per cent and lead to fatigue and impaired performance. Such diets also reduced performance timings and benefits due to increased oxygen utilization (fat oxidation uses more oxygen compared to carbs to provide adenosine triphosphate or ATP).
Under such circumstances, periodic carb meals can be included around training to support high-intensity activities. Having a strategic carb day can also help in fuelling the body with 300–350 grams of carbs per day. This also allows you to get back to ketosis easily once you are keto-adapted.
Moderate- and low-intensity exercise has been benefited from fat oxidation. During low-intensity activities, fat becomes the major source of fuel, and with a keto diet, there is increased efficiency of fat metabolism and usage. It also prevents muscle glycogen depletion, preventing the early onset of fatigue.
Ultimately, further research needs to be done on the keto diet or high-fat diet and its impact on athletes. However, there is little evidence of improving low-intensity activities and reducing weight.
Disclaimer: The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention or alleviation of any disease, disorder or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns and before undertaking a new healthcare regimen including making any dietary or lifestyle changes.
- Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability.
- High-Fat Ketogenic Diets and Physical Performance: A Systematic Review.
- The Effects of a Ketogenic Diet on Athletes.
- Ketogenic low-CHO, high-fat diet: the future of elite endurance sport?
- Effects of 30 days of ketogenic diet on body composition, muscle strength, muscle area, metabolism, and performance in semi-professional soccer players.