Table 2.
Studies evaluating the effects of fasting diets on sleep and mood status.
| Study (ref.) | Study design | Fasting type & regimen | Subjects & No. | Comparison group & No. | Study duration/time points | Findings |
|---|---|---|---|---|---|---|
| Beaulieu (70) 2021 United Kingdom | RCT | Intermittent energy restriction: restricted energy to 25% on fast days & free food intake on feed days | Overweight or obese women N = 24 | Control group with continuous energy restriction N = 22 | Up to 12 weeks | Increased sleep duration on fast days at week 2 and the final week compared to the baseline. Increased sleep duration on fast days compared to feed days at week 2 |
| Currenti (81) 2021 Italy | Cross-sectional | TRF: eating time of 8 h during the last 6 months | Adults from general population N = 1,572 | No restricted time | — | No effect on sleep quality |
| Cienfuegos (82) 2022 United States | RCT | TRF: eating time of 4 or 6 h | Obese adults N = 35 | Control group (no meal timing restrictions) N = 14 | 8 weeks | No effect of either of regimens on sleep quality, sleep patterns (wake time, bed time, sleep duration, and sleep latency), and insomnia severity index |
| Grant (83) 2017 Australia | RCT | TRF: simulated night shift, eating at night, 12 h fasting during the day | Healthy adults N = 5 | Control group with no eating at night N = 5 | 4 consecutive days | Increased sleepiness in both groups. Elevated hunger, full feeling, and urge to eat in the subjects with “no eating at night.” Impaired performance in both groups but it was exacerbated in the comparison group |
| Hutchison (31) 2019 Australia | Crossover RCT | TRF: early condition (eating hours 8 a.m.–5 p.m.); delayed condition (eating hours 12 p.m.–9 p.m.) | Abdominal obese male adults N = 8 | Control group with ad libitum diet for 7 days N = 7 | 7 days | No change of sleep duration compared to the baseline in either TRF condition |
| Parr (84) 2020 Australia | Pre-post non-randomized RCT | TRF: eating window (10 a.m.–7 p.m.) | Overweight or obese subjects with type 2 diabetes N = 19 | Baseline with routine diet for 2 weeks | 4 weeks | No effect on mental well-being indicators including sleep quality, duration, disturbance, and day-time sleepiness. No significant change was shown for additional indicators including quality of life, depression, anxiety, and stress of patients |
| Kesztyus (85) 2020 Germany | Before-after RCT | TRF: eating window of 8–9 h and nightly fasting period of 15 to 16 h | Healthy subjects N = 61 Abdominal obese subjects N = 38 |
Baseline | 3 months | Increased HRQoL and sleep quality but no alteration of sleep duration |
| Kalam (86) 2021 United States | Pre-post non-randomized RCT | ADF: 600 kcal “fast day”; ad libitum diet “non-fast day” combined with restricted carbohydrate intake to 30% | Obese pre- or postmenopausal women N = 31 | Baseline period with usual diet and exercise routines for 1 month | Weight loss period: months 0–3 Weight maintenance period: months 3–6 |
In comparison to the baseline no change in sleep quality, ISI, wake time, bed time, and sleep duration was found by month 3 or 6 |
| Teong (27) 2021 Australia | Parallel RCT | Calorie-restricted (CR) diet versus an IF diet IF, prescribed at 70% calculated energy requirements (CER) 3 times a week (fasting days) and 100% of CER on non-fasting days; CR, prescribed at 70% of CER | Overweight or obese but healthy women N (IF) = 22 N (CR) = 23 |
Baseline | 8 weeks | No significant difference of mean changes regarding sleep quality, quality of life, mood status, and cognition was observed when comparing IF versus CR |
| BaHammam (87) 2003 Saudi Arabia | Cross-sectional | Ramadan fasting (RF): abstinence from all food or drink from dawn to sunset | Healthy medical students N = 56 | Baseline 1 week before Ramadan with normal dietary routine | 4 time points: Week before Ramadan, the first week, second week, and third week of Ramadan | A greater daytime sleepiness during Ramadan |
| Almeneessier (88) 2019 Saudi Arabia | Cross-sectional | RF: abstinence from all food or drink from dawn to sunset | Healthy male volunteers N = 8 | Baseline 2 weeks before Ramadan with routine diet | 2 time points: 2 weeks before Ramadan, the first 3 weeks of Ramadan |
No difference in sleep time compared to the baseline. Delayed bed time and wake time in Ramadan |
| BaHammam (89) 2013 Saudi Arabia | Cross-sectional | RF: abstinence from all food or drink from dawn to sunset | Healthy male volunteers N = 8 | Baseline 1 week before Ramadan with normal dietary routine | 2 time points: 1 week before Ramadan, the first 2 weeks of Ramadan |
Delayed bed time and wake time during Ramadan. A significant decrease in total sleep time but no change in daytime sleepiness |
| Alghamdi (90) 2020 Saudi Arabia | Cross-sectional | RF: abstinence from all food or drink from dawn to sunset | Individuals with Type 2 Diabetes N = 36 | Seven consecutive days 2 weeks after the end of Ramadan | 2 time points: 1 week after Ramadan, 1 week in the middle of Ramadan |
A decrease in daily total sleep time and night sleep time in the middle of Ramadan |
| Bener (91) 2021 Turkey | Cross-sectional | RF: abstinence from all food or drink from dawn to sunset | Patients with hypertension N = 1,118 | Baseline 4 weeks before Ramadan | 2 time points: 4 weeks before Ramadan, 1 month after Ramadan |
No alteration in sleep time during Ramadan |
| de Toledo (92) 2019 Germany | Cross-sectional | Long-term or prolonged fasting: 4–21 days of Buchinger periodic fasting | Adults N = 1,422 | Baseline | 2 time points: At the baseline and after completing the fasting duration |
Enhanced physical and emotional well-being and no feeling of hunger |
| Hussin (93) 2013 Malaysia | RCT | Fasting and calorie restricted diet: a reduction of 300–500 kcal in daily energy intake combined with 2 days of Muslim Sunnah fasting per week for 3 months | Aging men N = 16 | Routine diet N = 15 | 12 weeks | Compared to the control, tension, anger, confusion, and total mood disturbance were significantly reduced in the intervention group and vigor was improved |
| Michalsen (94) 2006 United States | RCT | Periodic fasting: modified fasting period with restricted daily energy intake to maximum 300 kcal | In patients with mild to moderate chronic pain syndromes N = 36 | Control group (vegetarian meals with 2000 kcal/day) N = 19 | 8 days | A significant mood enhancement at the late study in fasted patients compared to the control. The feeling of hunger was mitigated over the study period for the majority of fasting patients |
| Kessler (95) 2018 Germany | NRCT | IF (24 h fasting/week): fasting once a week which was repeated every week for 8 weeks, with abstinence from solid food between 00:00 and 23:59 and energy intake restricted to maximum 300 kcal; routine diet on feed days | Healthy volunteers N = 22 | Control group with routine diet N = 14 | 6 months | No significant difference was found between intervention and control group at week 8 and after 6 months follow-up regarding mental health related outcomes such as positive mood, vigor, depression, tension, fatigue, and anger. Improved depression, anxiety, and HRQoL in the fasting group favor at the month 6 of follow-up |
| Gabel (96) 2019 United States | Pre-post non-randomized RCT | TRF: ad libitum food intake within an 8 h window (10:00–18:00) and fast (18:00–10:00) on a daily basis | Obese adults with BMI 35–40 kg/m2 N = 23 | Baseline 2 weeks with routine diet | 12 weeks | No significant changes in the adverse neurological outcomes including dizziness, weakness, fatigue, unhappiness, headache, and irritability |
| Kleckner (97) 2022 United States | Pre-post non-randomized RCT | TRF: daily 10 h window in accordance with their routine diet and preferences | Post-cancer treatment patients N = 36 | Baseline | 14 days | Improved fatigue and mood |
| Widhalm (98) 2017 Austria | Pre-post non-randomized RCT | ADF: a complete fasting day and normal food intake on the next day | Healthy overweight or obese individuals N = 9 | Baseline | 12 weeks | An improvement of mental well-being and vitality after 4 weeks from the baseline |
| Riat (99) 2021 Germany | Explaratory study | RF: fast the entire month of Ramadan from sunrise to sunset | Healthy participants N = 34 | Baseline (week before RF) | 6 time points: week before RF, day1, day14–16, and day27–29 of RF, week after RF, and month after RF | Enhancement in mood status and fatigue mediated by BDNF and cortisol |
| Alfahadi (100) 2020 Saudi Arabia | Case-control | RF: fasting the entire month of Ramadan for 15–16 h/day | Patients with T2DM N = 39 | Healthy subjects N = 43 | 2 time points: Between 15th and 22nd day of Ramadan, 2–3 after Ramadan |
No effect on fatigue severity when comparing during and post fasting periods. Fatigue severity of patients with T2DM during and after Ramadan was lower compared to the controls |
RCT, randomized clinical trial; TRF, time restricted feeding; WC, waist circumference; HRQoL, health-related quality of life; ADF, alternate day fasting; ISI, the insomnia severity index; IF, intermittent fasting; BDNF, brain-derived neurotrophic factor; T2DM, type 2 diabetes mellitus.