Skip to main content

Table 1 Descriptive results

From: A review of the ketogenic diet for endurance athletes: performance enhancer or placebo effect?

ReferenceSample sizePopulation, age rangeStudy designStudy lengthMethods
Diet compositionDiet provision & assessmentKetosis biomarkerTraining protocolVO2 Max protocol
Prospective trials
Burke et al. 2017 [12]N = 29Professional male race walkers with international race experience, 21–32 yearsSelf-selected diet
(non-random assignment)
3 weeksDiets:EAKD (< 50 g CHO, 75–80% FAT, 15–20% PRO [n = 10])a; HCD (60–65% CHO, 20% FAT, 15–20% PRO [n = 9])a; PCHO (60–65% CHO, 20% FAT, 15–20% PRO [n = 10])aPersonalized menus developed by professional chef and RDs. All foods provided/recorded by research team.Beta-hydroxybutyrate levels post-EAKD: 0.8–2.0 mmol/literOlympic-level training camp. Included daily race walking, resistance training, and/or cross training.Treadmill test
Carr et al. 2018 [7]N = 24Male (n = 17) and female (n = 7) elite race walkersSelf-selected diet
(non-random assignment)
3 weeksDiets:EAKD (< 50 g CHO, 75–80% FAT, 15–20% PRO [n = 9]); HCD (60–65% CHO, 20% FAT, 15–20% PRO [n = 8]); PCHO (60–65% CHO, 20% FAT, 15–20% PRO [n = 7])Menus developed by professional chef and RDs. All foods provided/recorded by research team.Elevated serum ketone bodies post-EAKD: 1 mmol/literSupervised, sport-specific, 3-week training protocol.Treadmill test
Heatherly et al. 2018 [13]N = 8Middle-age, recreationally competitive male runners, 39.5 ± 9.9 yearsPre-posttest3 weeksDiets:EAKD (< 50 g CHO, target 70% FAT [ad libitum]); HCD (habitual pre-study diet, reported as “moderate to high CHO”)Participants provided with daily macronutrient targets and instructed to self-track diet using diet software.Elevated serum ketone bodies post-dietary intervention compared to pre-EAKD levels: 0.7 ± 0.52 mmol/liter (EAKD) vs. 0.25 ± 0.09 mmol/liter (CHO)Participants continued normal recreational athletic activity for study duration.Treadmill test (pre-EAKD only). % baseline VO2 max at various race paces post-EAKD reported.
McSwiney et al. 2018 [14]N = 20Male endurance trained athletes (e.g., triathlon, cycling, marathon, ultra-marathon), 18–40 yearsSelf-selected diet
(non-random assignment)
12 weeksDiets:EAKD (< 50 g CHO, > 75% FAT, 10–15% PRO [n = 9]); HCD (65% CHO, 20% FAT, 14% PRO [n = 11])Participants received detailed handouts (e.g., example meal plans, shopping lists), nutrition counseling, and weekly check-ins. Weekly weighed food diary submitted.Beta-hydroxybutyrate levels post-EAKD: 0.5 mmol/liter≥ 7h hours of endurance exercise and 2 strength training sessions per week.Cycle ergometer test
Phinney et al. 1983 [15]N = 5Elite male cyclists, 20–30 yearsPre-posttest4 weeksDiets:EAKD (< 20 g CHO, 85% FAT, 15% PRO); HCD (1.75 g PRO/kg/day, remainder as 66% CHO and 33% FAT)aParticipants received three meals per day. Portions were weighed and intake monitored.Beta-hydroxybutyrate levels post-EAKD: 1.28 ± 0.35 mmol/literParticipants were asked to continue normal training, monitored via daily diary.Cycle ergometer test
Shaw et al. 2019 [16]N = 8Male endurance trained athletes (n = 2 marathoners, n = 4 ultra-marathoners, n = 2 triathletes), 29.6 ± 5.1 yearsRandomized repeated measures crossover study31-days (4.5 weeks) per condition with a 14- to 21-day washout periodDiets:EAKD (< 50 g CHO, 75–80% FAT, 15–20% PRO); HCD (43% CHO, 38% FAT, 19% PRO)aParticipants received education session with RD, info booklet, personalized menu plan, meal/snack examples, and lifestyle advice. All had daily contact with a registered dietitian for monitoring.Beta-hydroxybutyrate levels post-EAKD: ≥0.3 mmol/liter by day 3 and ≥ 0.5 mmol/liter by day 7Participants designed their own 28-day training plan (running and cycling) and were asked to replicate this during each dietary period.Treadmill test
Case studies
Zinn et al. 2017 [17]N = 5Recreational athletes involved in competitive endurance sport for 5+ years, 49–55 yearsPilot case study, mixed methods research10 weeksDiet:EAKD (< 50 g CHO, ad libitum FAT, 1.5 g/kg PRO [n = 5])Participants provided with daily macronutrient prescription and instructed to self-track diet using diet software.Beta-hydroxybutyrate levels: 0.5–4.2 mmol/literParticipants continued normal recreational athletic activity for study duration.Cycle ergometer test
  1. EAKD Endurance Athlete Ketogenic Diet, HCD High Carbohydrate Diet, PCHO Periodised carbohydrate diet: percentages based on weekly rather than daily diet, CHO Carbohydrate, PRO Protein, RD Registered dietitian
  2. aIsocaloric diets