Impact Of Ketogenic Diet On Athletes: Current Insights

Figures & data

Table 1 Endurance Capacity In Athletes Consuming A Ketogenic Diet At A Variety Of Intensities

Population & Study Design	Study Duration & Diet	Nutritional Ketosis	Performance Test & Nutrition	Advantage Of Ketogenic Diet
1A. Endurance capacity in trained endurance athletes consuming a ketogenic diet (KD) at moderate intensity (46–63% VO2max)
Phinney et al,^Citation6 Well-trained male cyclists >65 mL⋅kg⋅min^−1 Crossover design with order effect (control first)	4 weeks (28 days) HC (n=5: 57% CHO, 29% fat, 14% protein); KD (n=5: <20 g CHO, 85% fat, 15% protein)	Yes βHB 1.16–2.44 mM	TTE at 63% VO2peak Fasted	No decrement TTE 151 mins KD vs 147 mins HC (p>0.05)
1B. Endurance capacity in trained endurance athletes consuming a ketogenic diet (KD) at vigorous intensity (64–90 VO2max)
Burke et al,^Citation16 Elite race walkers 64 mL⋅kg⋅min^−1 Non-random parallel group design	3 weeks (21 days) HC (n=9: 65% CHO, 20% fat, 15% protein); PC (n=8: 65% CHO, 20% fat, 15% protein); KD (n=10: <50 g CHO, 78% fat, 15% protein)	Yes βHB >1.0 mM	10 km race HC & PC – 2 g⋅kg CHO prior, 60 g⋅h CHO during. KD energy equivalent LCHF snack	No HC groups 10 km time improved 124–190 sec (p<0.01), KD performance decreased 23 sec (p>0.05), NS between groups (p>0.05)
			Graded economy test (4 stages, treadmill)	No RER lower (p<0.001), and VO2 (p<0.01), HR (p<0.01), and RPE (p<0.01), increased stages 1–4 following KD
Shaw et al,^Citation17 Trained endurance athletes 59.4 mL⋅kg⋅min^−1 Crossover	4 weeks (31 days) HD (n= 8: 43% CHO, 38% fat, 19% protein), KD (n=8: 4% CHO, 78% fat, 18% protein)	Yes βHB 0.94 ± 0.45 mM	Run to exhaustion at 70% VO2max Fasted	No decrement TTE −6 mins HD (p=0.44), & −20 mins KD (p=0.36)
			Graded economy test (6 stages, treadmill) HC or HF meal prior; 55 g.h of CHO or coconut oil	No Efficiency maintained <60% VO2max. Energy expenditure (p<0.05), & oxygen consumption increased >70% VO2max (p<0.05)
1C. Endurance performance and capacity in recreationally active endurance athletes consuming a ketogenic diet at vigorous intensity (64–90 VO2max)
Heatherly et al,^Citation18 Recreationally active runners Crossover design with order effect (control first)	21 days KD (7% CHO, 64% fat, 29% protein) Fasted	Yes βHB ~0.7 mM (handheld meter)	50 min run, followed by outdoor 5 km TT	No decrement 5 km TT maintained (HC 23.92 ± 2.57 mins; KD 23.45 ± 2.25 mins, p=0.025) 2.5 kg weight loss (p<0.001)
McSwiney et al,^Citation19 Endurance athletes 53.6 mL⋅kg⋅min^−1 Non-randomized control trial	12 weeks (84 days) HC (n=11: 65% CHO, 20% fat, 14% protein); KD (n=9: <50 g/d CHO, 77% fat, 17% protein)	Yes βHB 0.5 mM	100 km TT HC or LC meal prior. HC consumed 30–60 g⋅h CHO; KD water + electrolytes during	No decrement 100 km TT maintained (HC −1.13 mins; KD −4.07 mins) (p=0.057)

Abbreviations: VO_2max, maximal oxygen uptake; mL⋅kg⋅min⁻¹, milliliters per kilogram bodyweight per minute; HC, high carbohydrate; CHO, carbohydrate; g, gram; KD, ketogenic diet; βHB, beta-hydroxybutyrate; mM, millimoles per liter; TTE, time to exhaustion; VO_2peak, peak oxygen consumption; min, minute; PC, periodized carbohydrate; km, kilometer; LCHF, low-carbohydrate high fat; NS, non-significant; RER, respiratory exchange ratio; HR, heart rate; HD, habitual diet; HF, high fat; g.h, grams per hour; TT, time trial.

Table 2 Strength Performance In Athletes Consuming a Ketogenic Diet At A Variety Of Intensities

Population & Study Design	Study Duration & Diet	Nutritional Ketosis	Performance Test & Nutrition	Advantage Of Ketogenic Diet
2A. Strength performance in trained athletes consuming a ketogenic diet at moderate (50–69% 1RM) to vigorous intensity (70–84% 1RM)
Paoli et al,^Citation20 Elite male artistic gymnasts Crossover design	4 weeks (30 days) WD (n=8: 47% CHO, 39% fat,15% protein); KD (n=8: <25 g CHO, 55% fat, 41% protein)	Not measured	Squat jumps All fasted	No decrement WD 0.0 r; KD 0.0 r (p>0.05)
			Countermovement jumps	No decrement WD −0.0 r; KD 0.0 r (p>0.05)
			Reverse grip chin-ups	No decrement WD 0.0 r; KD +0.4 r (p>0.05)
			Push ups	No decrement WD +6.5 r; KD + 2.8 r (p>0.05)
			Legs closed barrier test	No decrement WD +1.2 r; KD +2.5 r (p>0.05)
			Parallel bar dips	No decrement WD +4.0 r; KD +2.4 r (p>0.05)
Rhyu and Cho^Citation21 Taekwondo athletes Randomized control trial	3 weeks (21 days) HC (n=10: 40% CHO, 30% fat, 30% protein); KD (n=10: 4% CHO, 55% fat, 41% protein)	Not measured	Grip test All fasted	No decrement Left: NKD +0.6 N; KD 0.0 N (p>0.05) Right: NKD −1.6 N; KD −0.5 N (p>0.05)
			Back muscle strength	No decrement NKD +5.1 N; KD +3.3 N (p>0.05)
			Sit-up test (60 s)	No decrement NKD +1.5 r; KD +5.3 r (p>0.05)
2B. Strength performance in trained athletes consuming a ketogenic diet at near-maximal to maximal intensity (>85% 1RM)
Wilson et al,^Citation22 Resistance trained males Randomized control trial	10 weeks WD (n=12: 50% CHO, 30% fat, 20% protein), KD (n=13: 5% CHO, 75% fat, 20% protein)	Yes βHB 0.5–1.0 mM (handheld meter)	1RM bench press Both fasted	No decrement WD +5.5%; +3.3% KD 1RM bench
			1RM back squat	No decrement WD +10%; +5.4% KD 1RM squat
	Weeks 10–11 WD remained unchanged; KD (20% CHO, 40% fat, 20% protein)	No	1RM bench press Both fasted	Yes KD +4.5% (p<0.05); WD unchanged (p>0.05)
			1RM back squat	Yes KD +4% (p<0.05), WD unchanged (p>0.05)
Greene et al,^Citation23 Intermediate to elite competitive lifting athletes Crossover design	12 weeks UD (n=12: 49% CHO, 33% fat, 22% protein); KD (8n = 12: 8% CHO, 69% fat, 23% protein)	Yes βHB 0.4 ± 0.2 mM (handheld meter)	1RM: snatch + clean + jerk + squat + bench + deadlift = “lifting performance“ All fasted	No decrement Lifting performance minus ~0.5% KD (p>0.05)
2C. Strength performance in recreationally trained athletes consuming a ketogenic diet at near-maximal to maximal intensity (>85% 1RM)
Kephart et al,^Citation24 CrossFit Trainees Non-randomized control trial	90 days (12 weeks) HC (n=5: n/a); KD (n=7: 6% CHO, 77% fat, 17% protein) Pre-exercise meal(s) not controlled (g/kcal)	Yes βHB ~1.0 mM (handheld meter)	1RM back squat All Fasted	No decrement HC +5 kg; KD 0 kg (p=0.422)
			1RM power clean	No decrement HC +1 kg; KD −2 kg (p=0.347)
			Max push up test	No decrement HC +8 r; KD +8 r (p=0.716)

Abbreviations: WD, western diet; CHO, carbohydrate; KD, ketogenic diet; HC, high carbohydrate; r, repetitions; NKD, non-ketogenic diet; N, newtons; βHB, beta-hydroxybutyrate; mM, millimoles per liter; 1RM, one-repetition maximum; kg, kilogram; UD, usual diet; MD, mixed diet.

Table 3 Short-Duration Exercise In Athletes Consuming a Ketogenic Diet At A Variety Of Intensities

Population & Study Design	Study Duration & Diet	Nutritional Ketosis	Performance Test & Nutrition	Advantage Of Ketogenic Diet
3A. Short-duration (>30 s) vigorous exercise in athletes consuming a ketogenic diet
Rhyu and Cho^Citation21 Taekwondo athletes Randomized control trial	21 days Diet – see Table 2A	Not measured	2000 m run	Yes NKD unchanged +1.4 s; KD −32 s (TxG, p<0.05)
3B. Short-duration (>30 s) vigorous exercise in recreationally trained athletes consuming a ketogenic diet
Kephart et al,^Citation24 CrossFit trainees Non-randomized control trial	90 days (12 weeks) Diet – see Table 2C	Yes βHB ~1.0 mM (handheld meter)	400 m outdoor run Pre-exercise meal(s); not controlled (g/kcal)	No decrement WD +0.6 sec; KD +0.1 sec (p=0.326)
McSwiney et al,^Citation19 Endurance athletes Non-randomized control trial	12 weeks Diet – see Table 1C	Yes βHB 0.5 mM	CPT (3 min sprint)	Yes CPT relative peak power increased in KD (p=0.047). CPT average power (p=0.336) *Note: KD had greater body fat (kg) at baseline (p<0.05)
Cipryan et al,^Citation25 Moderately trained males Randomized control trial	4 weeks (28 days) HD (n=9; 48% CHO, 35% fat, 17% protein); KD (n=9; 8% CHO, 63% fat, 29% protein)	Yes βHB 0.4–0.7 mM (handheld meter)	Graded exercise test TTE	No decrement HD +1.8 min; KD +2.5 mins (ES ± 90% CI = −0.1 ± 0.3) HD −0.8 kg; KD −4.7 kg, 75–95% CI
			5 x 3 min interval sprints at 100% VO2max; 1.5 mins recovery	No decrement RER decreased (HD −0.01 RER; KD −0.1 RER; ES ± 90% CI = −1.5 ± 0.1), but mean % VO2max unchanged (HD = +0.6%; KD = -0.1%; ES ± 90% CI = 0.0§ ± 0.0)
Dostal et al,^Citation26 Non-randomized parallel group Recreationally trained men and women	12 weeks (n=12, 46% CHO, 35% fat, 19% protein); KD (n=12, 8% CHO, 69% fat, 23% protein)	Yes βHB >0.5 mM (handheld meter)	Graded exercise test TTE	No decrement +82 sec (p=0.005) increase in TTE within KD and +69 sec (p=0.018) in HC groups HC −0.9 kg; KD −3.6 kg
3C. Sprint-near maximal exercise (<30 s) in athletes consuming a ketogenic diet
Rhyu and Cho^Citation21 Taekwondo athletes Randomized control trial	21 days Diet – see Table 2A	Not measured	Wingate	No decrement NKD −0.61 w/kg, KD −1.05 w/kg (p>0.05)
			100 m sprint	No decrement NKD +0.22 sec, KD +0.18 sec (p>0.05) *Note: KD lost greater body mass (NKD −2.5 kg; KD −3.7 kg); may have confounded weight bearing tests (2000/100 m sprints)
3D. Sprint-near maximal exercise (<30 s) in recreationally trained athletes consuming a ketogenic diet
McSwiney et al,^Citation19 Endurance athletes Non-randomized control trial	12 weeks Diet – see Table 1C	Yes βHB 0.5 mM	SS Sprint Test nutrition – see Table 1C	Yes SS peak power increased KD (+0.8 w/kg), & unchanged HC (−0.1 w/kg) (p=0.025)
Dostal et al,^Citation26 Non-randomized parallel group	12 weeks Diet – see Table 3B	Yes βHB >0.5 mM (handheld meter)	30-15 Intermittent Fitness Test	No decrement TTE increased in KD (158.1 sec, BF10 ≥100; p=0.001) and HC (116.5 sec, BF10 ≥100; p=0.001)

Note: Evidence categories were; 1 no evidence, 1–3 anecdotal evidence, 3–10 moderate evidence, 10–30 strong evidence, 30–100 very strong evidence, and >100 decisive evidence.

Abbreviations: VO_2max, maximal oxygen uptake; m, meter; NKD, non-ketogenic diet; KD, ketogenic diet; sec, second; w/kg, watts per kilogram; kg, kilogram; βHB, beta-hydroxybutyrate; mM, millimoles per liter; CPT, critical power test; SS, six-second sprint; HC, high carbohydrate; WD, western diet; HD, habitual diet; TTE, time to exhaustion; ES, effect size; CI, confidence interval; VO_2peak, peak oxygen consumption; RER, respiratory exchange ratio; AP, absolute power; BF₁₀, Bayes Factor (statistical index that quantifies evidence of hypothesis, compared to alternative hypothesis).

Table 4 Body Composition In Athletes Consuming a Ketogenic And Non-Ketogenic Diet With Matched Protein Intakes

Population & Study Design	Study Duration & Diet	Nutritional Ketosis	Performance Test & Nutrition	Advantage Of Ketogenic Diet
4A. Body composition in trained athletes consuming a ketogenic diet
Wilson et al,^Citation22 Resistance trained males Randomized control trial	10 weeks Diet – see Table 2B Protein matched: yes WD 1.7 g⋅kg protein; KD 1.6 g⋅kg protein (p>0.05)	Yes βHB 0.5–1.0 mM (handheld meter)	(Measure: DXA) Fat mass	No decrement WD −1.8 kg; KD −4 kg (both, p<0.0001)
			(Measure: DXA) Lean body mass	No decrement WD +2.7 kg, and KD +1.5 kg (both, p<0.01) Advantage of CHO refeed
	Weeks 10–11 Protein matched: yes WD 1.6 g⋅kg protein; KD 1.6 g⋅kg protein (p>0.05)	No	(Measure: DXA) Fat mass	No KD increased fat mass p<0.0001); WD unchanged
			(Measure: DXA) Lean body mass	Yes KD +3 kg (p<0.0001); WD unchanged
4B. Body composition in recreationally trained athletes consuming a ketogenic diet
Vargas et al,^Citation27 Healthy individuals Randomized control trial	8-week NKD (55% CHO, 25% fat, 20% protein); KD (10% CHO, 70% fat, 20% protein) Protein matched: g and g⋅kg protein not displayed	Yes (urinary ketones; not outlined)	(Measure: DXA) Fat mass	Yes NKD (−0.4 kg, p>0.05); KD (−1.1 kg p<0.05)
			(Measure: DXA) Lean body mass	No NKD +1.4 kg, KD +0.3 kg (TxG p=0.025)

Abbreviations: WD, western diet; KD, ketogenic diet; g⋅kg, gram per kilogram; mM, millimoles per liter; DXA, dual-energy X-ray absorptiometry; kg, kilogram; NKD, non-ketogenic diet; CHO, carbohydrate; TxG, time x group.

Phinney S, Bistrian B, Evans W, Gervino E. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolism. 1983;32(8):769–776. doi:10.1016/0026-0495(83)90106-36865776

 PubMed Web of Science ®Google Scholar

Burke L, Ross M, Garvican-Lewis L, et al. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiol. 2017;595(9):2785–2807. doi:10.1113/JP27323028012184

 PubMed Web of Science ®Google Scholar

Shaw DM, Merien F, Braakhuis A, Maunder E, Dulson DK. Effect of a ketogenic diet on submaximal exercise capacity and efficiency in runners. Med Sci Sports Exerc. 2019;51:2135–2146. doi:10.1249/MSS.000000000000200831033901

 PubMed Web of Science ®Google Scholar

Heatherly AJ, Killen LG, Smith AF, et al. Effects of ad libitum low carbohydrate high-fat dieting in middle-age male runners. Med Sci Sports Exerc. 2017. doi:10.1249/MSS.0000000000001477

 Web of Science ®Google Scholar

McSwiney FT, Wardrop B, Hyde PN, LaFountain RA, Volek JS, Doyle L. Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism. 2018;81:25–34. doi:10.1016/j.metabol.2017.10.01029108901

 PubMed Web of Science ®Google Scholar

Paoli A, Grimaldi K, D’Agostino D, et al. Ketogenic diet does not affect strength performance in elite artistic gymnasts. J Int Soc Sports Nutr. 2012;9:34. doi:10.1186/1550-2783-9-3422835211

 PubMed Web of Science ®Google Scholar

Rhyu H, Cho S. The effect of weight loss by ketogenic diet on the body composition, performance-related physical fitness factors and cytokines of Taekwondo athletes. ‎J Exerc Rehabil. 2014;10(5):326–331. doi:10.12965/jer.14016025426472

 PubMedGoogle Scholar

Wilson JM, Lowery RP, Roberts MD, et al. The effects of ketogenic dieting on body composition, strength, power, and hormonal profiles in resistance training males. J Strength Cond Res. 2017;1. doi:10.1519/JSC.000000000000193528005635

 PubMed Web of Science ®Google Scholar

Greene DA, Varley B, Hartwig T, Chapman P, Rigney M. A low carbohdyrate ketogenic diet reduces body weight without compromising performance in power lifting and Olympic weightlifting athletes. J Strength Cond Res. 2018;00(00):1–10. doi:10.1519/JSC.0000000000002904

 Web of Science ®Google Scholar

Kephart WC, Pledge CD, Roberson PA, et al. The three-month effects of a ketogenic diet on body composition, blood parameters, and performance metrics in crossfit trainees: a pilot study. Multidiscip Digital Publishing Inst. 2018;6(1):1-11.

 Google Scholar

Cipryan L, Plews DJ, Ferretti A, Maffetone PB, Laursen PB. Effects of a 4-week very low-carbohydrate diet on high-intensity interval training responses. J Sports Sci Med. 2018;17:259–267.29769827

 PubMed Web of Science ®Google Scholar

Dostal T, Plews DJ, Hofmann P, Laursen PB, Cipryan L. Effects of a 12-week very-low carbohydrate high-fat diet on maximal aerobic capacity, high-intensity intermittent exercise, and cardiac autonomic regulation: non-randomized parallel-group study. Front Physiol. 2019;10. doi:10.3389/fphys.2019.00912

 Web of Science ®Google Scholar

Vargas S, Romance R, Petro JL, et al. Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial. J Int Soc Sports Nutr. 2018;15(1):1–9. doi:10.1186/s12970-018-0236-929311763

 PubMed Web of Science ®Google Scholar