Skip to main content

Table 1 Descriptive results

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

Reference

Sample size

Population, age range

Study design

Study length

Methods

Diet composition

Diet provision & assessment

Ketosis biomarker

Training protocol

VO2 Max protocol

Prospective trials

Burke et al. 2017 [12]

N = 29

Professional male race walkers with international race experience, 21–32 years

Self-selected diet

(non-random assignment)

3 weeks

Diets: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])a

Personalized menus developed by professional chef and RDs. All foods provided/recorded by research team.

Beta-hydroxybutyrate levels post-EAKD: 0.8–2.0 mmol/liter

Olympic-level training camp. Included daily race walking, resistance training, and/or cross training.

Treadmill test

Carr et al. 2018 [7]

N = 24

Male (n = 17) and female (n = 7) elite race walkers

Self-selected diet

(non-random assignment)

3 weeks

Diets: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/liter

Supervised, sport-specific, 3-week training protocol.

Treadmill test

Heatherly et al. 2018 [13]

N = 8

Middle-age, recreationally competitive male runners, 39.5 ± 9.9 years

Pre-posttest

3 weeks

Diets: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 = 20

Male endurance trained athletes (e.g., triathlon, cycling, marathon, ultra-marathon), 18–40 years

Self-selected diet

(non-random assignment)

12 weeks

Diets: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 = 5

Elite male cyclists, 20–30 years

Pre-posttest

4 weeks

Diets:EAKD (< 20 g CHO, 85% FAT, 15% PRO); HCD (1.75 g PRO/kg/day, remainder as 66% CHO and 33% FAT)a

Participants received three meals per day. Portions were weighed and intake monitored.

Beta-hydroxybutyrate levels post-EAKD: 1.28 ± 0.35 mmol/liter

Participants were asked to continue normal training, monitored via daily diary.

Cycle ergometer test

Shaw et al. 2019 [16]

N = 8

Male endurance trained athletes (n = 2 marathoners, n = 4 ultra-marathoners, n = 2 triathletes), 29.6 ± 5.1 years

Randomized repeated measures crossover study

31-days (4.5 weeks) per condition with a 14- to 21-day washout period

Diets:EAKD (< 50 g CHO, 75–80% FAT, 15–20% PRO); HCD (43% CHO, 38% FAT, 19% PRO)a

Participants 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 7

Participants 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 = 5

Recreational athletes involved in competitive endurance sport for 5+ years, 49–55 years

Pilot case study, mixed methods research

10 weeks

Diet: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/liter

Participants 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