Table 1.
Summary of studies evaluating the effects of intermittent fasting on physical performance and body composition.
| Reference | Parameters | Participants | Age | Trial Length & Intervention | Aerobic Changes | Anaerobic Changes | Strength Changes | Body Composition Changes (Secondary Outcome) |
|---|---|---|---|---|---|---|---|---|
| [34] | BC; VO2max; VE; VCO2; R; HR; Blood sample. | 6 physically active men (A). 7 sedentary men (S). | Group A, 35.5 ± 1.6 years Group S, 37.6 ± 2.3 years | 1 week before RF. 2 weeks after the start of RF. 4th week of RF. | ↓ HR (submax exercise) in S group during Ramadan. Significant ↓ of HR (submax exercise) in A group during Ramadan. | - | - | Total BM and FM ↓ non-significantly in both groups. |
| [4] | Anaerobic power; Anaerobic capacity; HR; BC; Blood lactate. | 10 male elite power athletes | 22.3 ± 1.3 years | 3 days before Ramadan (pre-RF). The last 3 days of Ramadan (end-RF). The last 3 d of the 4th week after the end of Ramadan (post-RF). | - | No adverse effects on anaerobic power and capacity. | - | No significant differences in body weight, BM index, FFM, % of body fat (↑ 0.2%). |
| [35] | Pmax; Pmean; Ppeak; BC. | 12 healthy males | 22.6 ± 1.3 years | 1 week before Ramadan. 2nd week of Ramadan. 4th week of Ramadan. 2 weeks after Ramadan. | - | Negative effect of Ramadan on anaerobic performance during the afternoon and evening. No effect on anaerobic performance in the morning. | - | No significant changes for body mass. |
| [36] | Speed; Power; Agility; Endurance; Passing and dribbling skills | 85 junior soccer players | 18.0 years | 3 weeks before Ramadan. 2nd week of Ramadan. 4th week of Ramadan. 3 weeks after Ramadan. | No change in fasted 10 or 30 m run during the afternoon, but ↑ fatigue index during Ramadan. | - | ↑ in vertical jump height from pre-Ramadan to the 2nd and 4th week of Ramadan, especially in the afternoon. Significant ↑ in vertical jump performance from pre-to post-Ramadan, especially in the afternoon. | - |
| [10] | Mean speed; Mean HR; Distance covered in 30 min TT run; Physiological variables taken before and after the 60 min exercise runs. | 10 moderately trained male runners | 27.3 ± 7.2 years | 1 week before Ramadan. During Ramadan. 1 week after Ramadan. | Shorter distance covered during the 30 min TT run during Ramadan. | - | - | - |
| [17] | VO2max; Submaximal VO2 kinetics; Anthropometric parameters; MVC; Running efficiency; Running Performance | 18 well-trained Muslim runners (EG, n = 9; CG, n = 9) | 23.6 ± 2.9 years | 1 week before Ramadan. Last week of the fasting period. After Ramadan. | Significant ↓ in running speed at VO2max in the EG. No changes in VO2max or running efficiency. Significant improvement of VO2 kinetics in EG. Significant ↓ in 5000 m running in EG. | - | No significant difference was observed in MVC between groups. Significant ↓ in MVC was observed, after Ramadan, only in the EG. | No significant differences on BM and FM between groups before and after (EG ↓ 0.8% FM; CG ↓ 1.3% FM). |
| [21] | PA; BC; Muscle force; EMG activity. | 11 moderately active Muslim males | 31.0 ± 3.0 years | 1 month and 1 week before Ramadan. During Ramadan. 1 month after Ramadan. | - | - | Maximal force was maintained during Ramadan. Maximal isometric torque measurements were not significantly different between sessions for both the knee extensors and flexors. | Little influence of Ramadan on BM and BC. |
| [37] | Upper arm girth; Isometric strength; Blood sample; RPE; BMI. | 29 participants (19 men, 12 women). Post-prandial group (n = 5 men, n = 5 women). Fasting group (n = 12 men, n = 7 women) |
22.0 ± 3.3 years | Pre-fasting. Post-fasting - session #1, 2, 3, 4 and 5. (8 h water-only fast) | - | - | Upper arm girth ↑ significantly within each group. Elbow extension and isometric strength ↓ significantly over time within each group. Less induction of muscle damage (EG). | BMI was similar between groups and sessions. |
| [38] | Wmax-A; Wmax-L; VJH; HGF; Anthropometric data; Hemoglobin and hematocrit | 20 trained men (RF, n = 10). (CG, n = 10) | RF, 21.8 ± 1.9 years; CG, 20.5 ± 1.0 years | Before Ramadan. End of the 1st week of Ramadan (R1). During the 4th week of Ramadan (R4). | - | - | Significant ↓ in the Wmax-A and Wmax-L during Ramadan. No significant change in VJH and HGF during Ramadan. | BM and BM index was ↓ at R1 and R4. FM was lower at R4 (↓0.3%).e |
| [39] | VO2max; MAP; Reaction time; Anthropometric variables. | 10 adolescents karate athletes | 18.5 ± 0.5 years | 3 weeks before Ramadan. At the end of the first week of Ramadan. During the 4th week of Ramadan. 3 weeks after Ramadan. | No significant changes at VO2max, MAP and HRmax during Ramadan. No effect on reaction time. | - | - | No significant changes in BM and FM during Ramadan. |
| [9] | VO2max; HIE; Flexibility; Agility; Vertical jump; Handgrip strength. | 77 untrained Muslim men (EG, n = 37; CG, n = 40) | EG, 22.6 ± 1.8 years. CG, 23.0 ±1.5 years | 1 week pre-Remadan. During Ramadan. 2 weeks post-Ramadan. | Significant ↓ in VO2max. | Significant ↓ in HIE | Vertical jump did not show any alteration. Non-significant variation in handgrip strength. | ↓ BM, but not significant. |
| [40] | Ventilatory variables; Metabolic variables. | 16 healthy and active men (FAST, n = 8) (FED, n = 8) | FAST, 20.9 ± 2.0 years; FED, 21.3 ± 2.5 years | 3 d/week for 6 weeks in the fasted state (Night fast) | Significant ↑ of VO2max for both groups. ↓of time to run 3000 m (EG and CG). | - | - | Fat oxidation was not modified by training. |
| [6] | TRF; ND; BC; Strength; Blood sample. | 34 resistance-trained males (TRF, n = 17; ND, n = 17) | TRF, 29.2 ± 3.8 years; ND, 28.5 ± 3.5 years | Tested 8 weeks pre-RT. 8 weeks of TRF. Tested 8 weeks post-RT. (Intermittent fast 8/16 h) | - | - | Maintained in TRF and ND. | Significant ↓ FM TRF (−16.4%); FFM was maintained in TRF and ND. |
| [41] | Maximal speed; Mean speed; Maximal power; Mean power; Vertical stiffness; Vertical COM; FI; Blood sample; HR; Body mass; RPE; | 21 active males | 29.8 ± 5.9 years | Fed/control session (pre-3 d of IF). 3 d of IF. | - | Significant effect of fasting on maximal and mean speed, maximal and mean power, vertical stiffness and vertical COM displacement. Sprint speed and mean power significantly ↓ from the CG. 3 d of IF impaired speed and power through a ↓ in vertical stiffness. | - | No significant changes on BM loss. |
| [2] | RT-TRF; BC; Muscle strength. | 18 active men (RT-TRF, n= 10; RT-ND, n = 8) | RT-ND, 22.0 ± 2.4 years. RT-TRF, 22.9 ± 4.1 years | 8 weeks of RT-ND. 8 weeks of RT-TRF. TRF for 4 d/week. Analysis 4 and 8 weeks post study. (No fasting on training days; intermittent fasting on non-training days 4/20 h) | - | - | ↑in upper and lower body muscle strength in ND and TRF groups, but ↑ were better in RT-TRF group. No changes after 4 weeks. | TRF-RT group lost up to 5.5% and 22% of initial BM and FM, respectively. |
| [42] | VO2max; HRmax; MVIC; BC; Sleep; Tre; Tsk; RPE; Blood markers; Training load. | 14 male trained Muslim football players | 21.8 ± 2.4 years | Before Ramadan. During Ramadan. After Ramadan. | mLIST were significantly faster in both CG (before and after Ramadan) as compared to Ramadan fasting group. An adverse effect on prolonged performance during Ramadan fasting. |
- | Minimal ↓ in fatigue within the working muscles and in the neuromuscular activation. No changes were verifying in MVIC of the upper limb. No significant differences on knee extension MVIC over trials in each group. | BM at pre- and post-exercise was not significantly different before, during and after Ramadan. |
| [43] | VO2peak; Anaerobic power; BC; Blood sample; Urine sample. | 20 healthy male | EG, 21.0 ± 1.0 years; CG, 20.0 ± 1.0 years | 7 d of DS and EF. Baseline data (day 0). Day #2, 4, 6, 8, 10 (exercise test). (Intermittent fasting with lunch deprivation) | - | ↓ WnT power in EG during Day 2, Performance returned to baseline results from Day 4. HIT TTE in EG ↓throughout the 10-day period, but seems to recovered at the end of the experiment. | - | ↓ BM in the EG (−1.55%). |
| [11] | MVIC; Voluntary activation level; Neuromuscular efficiency Body mass. | 10 healthy male | 22.1 ± 2.0 years | Before Ramadan. During Ramadan. After Ramadan. | - | - | MVIC↓during Ramadan. Voluntary activation level↓during Ramadan. Neuromuscular efficiency remained unaffected by Ramadan. | BM remained unaffected by Ramadan. |
| [44] | VO2 peak, PO, PPO, Mean PO, FI, Blood samples, VT1, VT2 | 20 male cyclists (SIT FAST, n = 11; SIT CHO, n = 9). | SIT FAST, 33.3 ± 7.2 years SIT CHO 34.0 ± 8.2 years | SIT in overnight fasted state or with carbohydrate supplementation. Groups performed 3 times per week for 4 weeks. | PPO was significantly ↑ in SIT CHO compared to SIT FAST. No differences in post-training VO2 VT1 nor VT2 between groups. | - | - | - |
| [45] | VO2max; VCO2; HR; BM; Time to exhaustion; RER; Fat and CHO oxidation rate; Muscle and blood samples. | 20 young male. (Fasted state, n = 10; Fed state CHO, n = 10) | d.s | 6 weeks endurance training program, 4 days per week, in fasted or ingested CHO before and during training sessions. | VO2 max and time to exhaustion, between fasted and fed groups, were similar in the pre-test and ↑ 9% after training, but not significantly. | - | - | ↑ fat mass oxidation in fast group (+ 21%), but not significant. Body weight ↓ in both groups (not significantly). |
| [46] | VO2 peak; VO2; VCO2; RER; BM; Muscle and blood samples. | 20 moderately active males. (Fast, n = 10; CHO, n = 10) | 21.2 ± 0.4 years | Endurance training program, 6 weeks of 3 days per week, in fasted or CHO fed state. | VO2 peak ↑ within group but was not different between groups. | - | - | No significant changes on body mass loss. |
| [47] | VO2 peak; VO2; VCO2; RER; HR; Muscle and blood samples. | 8 males | 25 ± 2 years | Cycling in fasted state or 2 h following ingestion of CHO. | VCO2 ↓ significantly during fast exercise. VO2; HR and RER were not different during exercise between trials. | - | - | - |
| [48] | VO2 max; VO2 peak; biochemical analyses. | 8 females untrained 6 males untrained | 26.6 ± 5.8 years | 4 weeks of 5 days per week endurance cycle ergometer in overnight-fasted or acutely fed state. | Fast group showed ↑ in VO2 max than Fed group. Peak power ↑ more in fasted group compared to CG. | - | - | - |
| [49] | HR; Blood samples; Reaction time; cognitive performance. | 21 physically active, healthy Muslims males. | 29.8 ± 5.9 years | 3 days of IF | - | Simple and complex reaction times ↑ during the 3d-IF after 2 bouts of intensive RS. | - | - |
| [24] | Skeletal muscle hypertrophy; muscular performance; BM; FFM; Commonly physiological and metabolic variables. | 40 resistance trained females. (CG, n = 14; TRF, n = 13; TRFHMB, n13). | CG, 22.0 ±2.4 TRF, 22.1 ± 2.1 TRFHMB, 22.3 3.4 | 8 weeks of supervised RT in TRF state with or without HMB. | - | - | TRF did not attenuate FFM, muscle hypertrophy, or developments in muscle performance. | FFM ↑ in three groups without differences between all. Significant ↓ in FM in TRF group. |
| [50] | PA level; Anthropometric status; Body composition; Dietary information. | 33 healthy young males | 21.85 ± 1.87 years | Before Ramadan; 1st week of Ramadan; Last week of Ramadan. | Statistically significant ↓ in high intensity PA in 1st w of RF. Statistically significant ↓ in moderate PA in 1st w of RF compared with before RF. | - | - | Significant ↓ in BM and %FM at last week of RF compared to before RF. |
| [51] | CMJ; RS test; YYIRT1 | 30 amateur soccer players. (MTG, n = 10; ETG, n = 10; CG, n = 10) | 22.9 ± 1.3 years | Before Ramadan. After Ramadan. | - | After RF YYIRT1 ↑in the morning and in the evening. ↑in RS training (fasted state) in the morning or in the evening. But significant difference compared to before and after Ramadan in the morning. | No differences were observed in CMJ before and after RF for any group. | - |
| [52] | Blood samples; VO2 max; HR; BM; Endurance exercise performance; metabolic measurements; Mood state and daytime sleepiness. | 12 Muslims men runners. | 27.9 ± 7.2 years. | Endurance running performance during Ramadan, after ingesting LGI or normal mixed CHO food as sahur meal. | TT distance ran was statistically significant ↓ in LGI vs. CG. | - | - | No significant changes in BM. |
Abbreviations. BC, body composition; BIA, bioelectrical impedance analyser; BM, body mass; CG, control group; CHO, carbohydrate; CMO, vertical center of mass; DS, dietary standardization; d.s, did not say; EF, exercise familiarization; EG, experimental group; EMG, electromyography; ETG, evening training group; FFM, fat free mass; FI, fatigue index; FM, fat mass; HGF, handgrip force; HIE, high-intensity effort; HIT, high-intensity cycling test; HMB, β-hydroxy β-methylbutyrate supplementation; HR, heart rate; IPAQ, international physical activity level questionnaire; LGI, low glycemic index; MAP, maximal aerobic power; MAS, maximal aerobic speed; mLIST, Loughborough intermittent shuttle test; MTG, morning training group; MVC, maximal voluntary contraction; MVIC, maximal voluntary isometric contraction; ND, normal diet; PA, physical activity; Pmax, maximal power; Pmean, mean power; PO, power output; Ppeak, peak power; PPO, Peak power output; R, respiratory exchange ratio; RF, Ramadan fasting; RPE, rating of perceived exertion; RS, Repeated sprints, RT, resistance training; RT-ND, resistance training and normal diet; RT-TRF, resistance training with time-restricted feeding; SIT, sprint interval training; Tre, rectal temperature; TRF, time-restricted feeding; Tsk, skin temperature; TT, time trial; TTE, time-to-exhaustion; VE, ventilation; VCO2, carbon dioxide output; VJH, vertical jump height; VO2max, maximal oxygen consumption; VO2peak, peak oxygen consumption; VO2, oxygen consumption; VT1, first ventilatory threshold; VT2, second ventilatory threshold; Wmax-A, maximal anaerobic power of the arms; Wmax-L, maximal anaerobic power of the legs; WnT, Wingate test; YYIRT1, yo-yo intermittent recovery test level 1.