Keto for Athletes: What UK Sports Nutrition Guidance Says
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What does the evidence say about keto for athletes? The British Nutrition Foundation (BNF) says that "at the moment we do not have enough evidence to show that low-carbohydrate diets can benefit athletic performance." UK sports nutrition guidance from the BNF, the British Dietetic Association (BDA) and the UK Sports Institute sets carbohydrate by training load, starting at 3–5g per kg of body weight a day in each one's lowest band. A very low carb (ketogenic) diet is 20–50g of carbs a day in total, according to the BDA. If you train and are thinking about keto, speak to your GP or a registered dietitian first.
At a glance
- Not enough evidencethat low-carb diets benefit athletic performance, says the BNF
- 3–5g per kgcarbs a day in the lowest training band (BDA, BNF and UK Sports Institute)
- 210–350gcarbs a day in that band for a 70kg adult (our calculation)
- 20–50gcarbs a day on a very low carb (ketogenic) diet, per the BDA
On this page
This guide sets out what UK nutrition and sports bodies say about keto and low carb diets for people who train or compete, and where the evidence runs out. It isn't personal advice, and we're not suggesting keto for sport. For how much protein UK guidance suggests, see our guide to how much protein you need on keto, and for a wider look at the diet, our guide to the pros and cons of keto.
What does the evidence say about keto for athletes?
We haven't found guidance from the NHS, the BDA, the BNF or the UK Sports Institute that recommends a ketogenic diet for sport. The BNF answers the question "If I am doing endurance training, should I be following low carbohydrate, high fat diets?" on its sport and exercise page. It says: "Carbohydrate is important as an energy source during exercise. Having very low intakes of carbohydrate when exercising can cause low energy levels, loss of concentration, dizziness or irritability."
It goes on: "Because carbohydrate is important for providing energy during exercise, there is a benefit in ensuring enough is consumed. This is especially for high-intensity exercise where some studies have shown that performance is reduced when carbohydrate intakes are low. Some studies in specific exercise scenarios such as lower intensity training in endurance runners, have found beneficial effects of low carbohydrate diets on performance. However, these results have not been consistent and so at the moment we do not have enough evidence to show that low-carbohydrate diets can benefit athletic performance."
In its section on fat, the BNF adds: "There is ongoing research on the effects of higher fat/lower carbohydrate diets on athletic performance, and debate about the potential effects for different types of sporting events. For the general population, the advice would be to stick to the population guidelines stated above."
The BDA's sport and exercise fact sheet doesn't mention keto or low carb diets. On fuel, it says: "Carbohydrate is the main fuel source for exercising muscles. Requirements will depend on your training programme and overall dietary goals. Usually, higher amounts are needed to support harder and longer training sessions."
How many carbs does UK guidance suggest for training?
The BDA, the BNF and the UK Sports Institute each give carbohydrate in grams per kg of body weight a day, depending on how much and how hard you train. For lighter exercise, the BDA says: "If following a general fitness programme, your carbohydrate needs can be met by eating a normal healthy diet." For heavier training, it says: "If undertaking moderate or high-volume training (one intense session/multiple sessions per day) greater amounts are required. Not eating enough can lead to lack of energy, early fatigue during exercise, loss of concentration, increased injury risk and delayed recovery."
| Activity (BDA) | g/kg a day | 70kg adult |
|---|---|---|
| Keeping active: 1–2 hours of light to moderate activity 3–5 times a week, no performance goal | 3–5g | 210–350g |
| 2–3 hours a day of intense activity, 5–6 times a week | 5–8g | 350–560g |
| 3–6 hours a day of intense activity in 1–2 daily workouts, 5–6 days a week | 8–10g | 560–700g |
BDA Sport and exercise food fact sheet (May 2026). The 70kg column is our calculation (70 × the BDA's range). The BDA adds that "carbohydrate intakes should be fine-tuned with individual consideration of total energy needs, specific training and performance feedback."
The BNF and the UK Sports Institute use four bands instead: 3–5g, 5–7g, 6–10g and 8–12g per kg a day. Both start with light, low intensity or skill-based training at 3–5g. The BNF's top band, 8–12g, is for more than 4 hours a day of moderate to high intensity exercise.
For comparison, the BDA's low carb diets fact sheet puts a very low carb (ketogenic) diet at 20–50g of carbohydrate a day, and a low carb diet at 50–130g. The lowest training band in all three tables works out at 210–350g a day for a 70kg adult (our calculation).
The UK Sports Institute doesn't suggest the same high carbohydrate intake every day either. It recommends what it calls a "smart" carbohydrate diet: adjusting carbohydrate day to day and session by session to match the demands of training and competition.
What sports bodies say about endurance and strength
World Athletics, then called the IAAF, published a consensus statement on nutrition for athletes in 2019. A team of 50 experts was led by Lindy Castell of Green Templeton College, Oxford, and Louise Burke, Head of Sports Nutrition at the Australian Institute of Sport. One of the key findings listed in the World Athletics press release is: "The usefulness of high-fat, low-carbohydrate diets is limited to selected individuals, events or scenarios in distance events."
The International Society of Sports Nutrition (ISSN), a US-based organisation, published a position stand on ketogenic diets in 2024. It reviews keto in "healthy exercising adults" and says it "does not address the use of exogenous ketone supplements". Its position is that a ketogenic diet has largely neutral or detrimental effects on athletic performance compared with a diet higher in carbohydrates and lower in fat.
Endurance. The ISSN says: "The endurance effects of a ketogenic diet may be influenced by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet."
Strength. The ISSN says: "A ketogenic diet tends to have similar effects on maximal strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators." In the body of the paper, it adds that "there is a lack of trials exceeding 12 weeks involving highly trained strength athletes."
Limits of the evidence. The ISSN says: "There is insufficient evidence to determine if a ketogenic diet affects males and females differently." Its review left out a trial in adolescents. The paper's disclosure statement says the authors have no competing interests concerning it, but lists authors' work with supplement companies and that one author is a co-owner of Ketone Technologies LLC.
Protein for active people on keto
The BDA's sport and exercise fact sheet says: "Athletes participating in strength and endurance sports have a higher requirement for protein (approximately 1.4-2.0 g/kg/day) than people who don't exercise (0.75 g/kg/day)." For a 70kg athlete, 1.4–2.0g per kg is 98–140g of protein a day (our calculation). The BDA adds: "However, in most cases, providing energy requirements are met, a healthy, balanced diet should provide enough protein to meet any increased requirements."
On timing, the BNF says: "Between 30 minutes and 2 hours after training, it is recommended to consume 15-25g of protein alongside some carbohydrate." Our guides to protein on keto and whether whey protein is keto cover protein amounts and the carbs in protein powders.
Eating enough, and supplements
The UK Sports Institute's guidance for developing athletes says: "When energy intake is less than the energy needed by the body, an energy deficit is created and there is a low energy availability". It lists three situations where low energy availability may arise: training more without changing what you eat (or eating less without meaning to), restricted eating for weight control or loss of body fat, and disordered eating or eating disorders.
Among the signs of short-term energy deficiency, it lists low energy levels, poor mood and concentration, and an increased risk of injury and illness. It says: "prolonged energy deficiency in athletes can be described as a condition called Relative Energy Deficiency in Sport (RED-S), and there are some potentially serious consequences for both short and long-term health".
On supplements, the BDA says: "A varied, well-balanced diet should provide the nutrients and energy required for sport. Supplements will not compensate for poor food choices but may be helpful in certain situations." It adds: "If considering supplementation, consult a registered practitioner to ensure they are appropriate for you and you use them safely and effectively." The World Athletics press release says: "A food first philosophy is promoted in relation to nutritional needs, and supplements should only be used under supervision to treat or prevent nutrient deficiencies." It also warns of a risk of taking in banned substances with any supplement.
Who should get advice first
The BNF says: "For professional athletes, getting personalised nutrition advice from a qualified sports nutritionist or dietitian is likely to be an important part of their training support." The BDA says: "To get your nutrition right, you may find it useful to consult a registered sport dietitian or sport and exercise nutritionist." It points to the Sports and Exercise Nutrition Register (SENr) to find a qualified practitioner.
- Pregnancy. The BDA's low carb diets fact sheet says: "Ketogenic diets should not be followed by women who are pregnant."
- Type 2 diabetes and other conditions. The BDA says: "If you have type 2 diabetes, you may need to reduce some medication such as insulin or sulfonylureas to avoid hypoglycaemia, and this should be done under medical supervision." It also says that "if you have a medical condition you are advised to seek advice from a dietitian."
- Type 1 diabetes. University Hospitals Sussex NHS Foundation Trust says: "If you have type 1 diabetes and you want to reduce how much carbohydrate you eat, it is really important that you are supervised by a dietitian before you make this change, and while you are following this diet." It also says: "We do not recommend that people follow a very low carbohydrate diet, because at the moment there is no strong evidence that it is helpful for people with type 1 diabetes. But if you do want to try a very low carbohydrate diet (also called a ketogenic diet), we will support you with this." For people who do, it says: "Speak to your healthcare team so they can help you adjust your insulin to reduce your risk of hypos." On exercise, it says: "If you are doing planned physical activity, remember to reduce your insulin." and "If you are doing unplanned physical activity you may need to take extra carbohydrate."
- Under 18s. The ISSN position stand covers adults, and its review left out a trial in adolescents. The UK Sports Institute's guidance for developing athletes says: "Unless medically justified, no foods need to be avoided all together, as everything can be included in moderation. Athletes should focus on having a varied and balanced diet and a healthy relationship with food." If you're under 18, or coach or parent a young athlete, speak to a GP or registered dietitian before cutting out food groups.
- Eating disorders. The UK Sports Institute lists disordered eating or eating disorders as one of the situations where low energy availability may arise.
Speak to your GP, diabetes nurse or a registered dietitian before you make big changes to your diet. This is especially important if you have diabetes and take insulin or other medicines that can cause hypos, or take SGLT2 inhibitors, as your medication may need to change. The same goes if you're pregnant, breastfeeding or have a history of eating disorders.
Key takeaways
- Not enough evidence yet: the BNF says there isn't enough evidence that low-carb diets benefit athletic performance.
- UK guidance sets carbs by training load, from 3–5g per kg a day (210–350g for a 70kg adult, our calculation), against 20–50g a day on keto.
- International bodies are cautious: World Athletics says the usefulness of high-fat, low-carb diets is limited to selected cases in distance events, and the US-based ISSN describes keto's effects on performance as largely neutral or detrimental.
- Eat enough for your training: the UK Sports Institute links prolonged energy deficiency to RED-S.
- Get advice first if you're pregnant, under 18, have diabetes or have a history of eating disorders.
Frequently asked questions
Is keto good for athletes?
The British Nutrition Foundation says that "at the moment we do not have enough evidence to show that low-carbohydrate diets can benefit athletic performance." It also says that "some studies in specific exercise scenarios such as lower intensity training in endurance runners, have found beneficial effects of low carbohydrate diets on performance. However, these results have not been consistent".
How many carbs do athletes need?
The BDA's sport and exercise fact sheet gives 3–5g of carbohydrate per kg of body weight a day for keeping active with no performance goal, 5–8g for 2–3 hours of intense activity a day 5–6 times a week, and 8–10g for 3–6 hours of intense activity a day. A ketogenic diet is 20–50g a day in total.
Is keto suitable for endurance athletes?
World Athletics' 2019 consensus statement says: "The usefulness of high-fat, low-carbohydrate diets is limited to selected individuals, events or scenarios in distance events." The US-based International Society of Sports Nutrition says all the studies involving elite athletes showed a performance decrement on a ketogenic diet, though all lasted six weeks or less, and that further research is needed.
Does keto affect strength training?
The US-based International Society of Sports Nutrition says a ketogenic diet tends to have similar effects on maximal strength, and on strength gains from resistance training, as a diet higher in carbohydrates. It adds that a minority of studies show better results on the higher-carbohydrate diet, and that longer trials in highly trained strength athletes are lacking.
Who should get advice before trying keto for sport?
Speak to your GP or a registered dietitian first, especially if you're pregnant, under 18, have diabetes or have a history of eating disorders. The BDA says ketogenic diets should not be followed by women who are pregnant, and suggests a registered sport dietitian or sport and exercise nutritionist for sports nutrition advice.
Sources
- British Nutrition Foundation. Sport and exercise (low carbohydrate, high fat diets for endurance training; carbohydrate bands per kg; fat; protein after training; personalised advice for professional athletes). Checked 3 November 2026.
- British Dietetic Association. Sport and exercise food fact sheet (May 2026: carbohydrate needs by activity level, protein, supplements, registered practitioners) and Low carb diets food fact sheet (October 2019: types of low carb diet, pregnancy, medication and medical conditions).
- UK Sports Institute. Sports Nutrition Fundamentals To Improve Performance (guidance for developing athletes: carbohydrate bands, "smart" carbohydrate, low energy availability and RED-S, avoiding foods). Checked 3 November 2026.
- World Athletics. IAAF releases Consensus Statement on Nutrition for Athletes (17 April 2019: high-fat, low-carbohydrate diets; supplements).
- International Society of Sports Nutrition (US). International society of sports nutrition position stand: ketogenic diets, Journal of the International Society of Sports Nutrition (2024: performance, endurance, strength, limits of the evidence, disclosures).
- University Hospitals Sussex NHS Foundation Trust. Low and Very Low Carbohydrate Diets in Type 1 Diabetes (dietitian supervision, insulin and physical activity). Last reviewed 19 March 2025.
