Effect of Time-Restricted Eating on Sleep Quality and Body Composition: A Systematic Review

Abstract

Context

Time-restricted eating (TRE) is a dietary approach that consolidates energy intake in a restricted period during the day. It is an alternative approach to weight loss and might be important to sleep quality.

Objective

To review the current literature related to the effects of TRE on sleep quality and body composition in adults.

Data Sources

A literature search of the PubMed, Scopus, Web of Science (Clarivate), and Biblioteca Virtual em Saúde/Bireme databases was carried out until May 2024.

Data extraction

Reviewed articles included clinical, interventional (controlled or uncontrolled) studies including individuals older than 18 years, with no gender restriction. The interventions had to control feeding time, body composition could be assessed by any validated method, and sleep could be assessed by polysomnography, actigraphy, and validated sleep assessment questionnaires.

Data analysis

Eleven studies were included in this systematic review. Study samples varied between 19 and 137 participants, with a predominance of female participants in 10 studies. Seven of the studies (58.3%) tested an intervention of 8 hours of TRE, with an intervention range of between 4 weeks and 12 months. All studies observed weight loss. Nine studies showed reductions in fat mass, including 2 studies that observed reductions in visceral fat mass. No studies, independently of weight loss or body composition changes, objectively observed changes in sleep duration after TRE interventions. However, in the subjective evaluation, 1 study found a reduction in sleep duration of 30 ± 13 minutes, an increase in latency of 7 ± 3 minutes, and a reduction in sleep efficiency of 2% ± 1% in the group treated with TRE compared with the control group.

Conclusion

Time-restricted eating seems to be effective in weight loss and fat mass reduction, but most studies found no effect on sleep parameters. There was a lack of standardized methods for sleep measurements in the reviewed studies. However, these results could provide valuable data for the design and formulation of new well-founded studies assessing sleep using objective methods and including different sleep parameters.

Systematic Review Registration

PROSPERO registration No. CRD42024524598.

INTRODUCTION

Modern lifestyle choices have been associated with behaviors that disrupt circadian rhythms. Inconsistent mealtimes and late eating, with meals close to rest time, seem to influence weight gain.¹ The study by Gil and Panda² shows that more than half of adults eat during a window of 15 hours or more every day and restricting this time would contribute to reducing body weight and improving sleep.

Time-restricted eating (TRE) is a type of intermittent fasting, based on the circadian rhythm, that consists of restricting food intake to fewer daily hours and extending fasting at the beginning of the night and in the first hours in the morning.³ Time-restricted eating contributes to a reduction in body weight without a significant modification in energy intake or diet composition, making it a viable alternative weight management and obesity treatment.⁴ The current literature also shows other benefits, such as improving insulin levels, blood pressure, lipid profile, and oxidative stress.^5,6

A recent systematic review demonstrated that intermittent fasting is effective in reducing body weight, total body fat, and visceral fat mass,⁷ and TRE alone or in combination with caloric restriction with an eating window of 6-8 hours contributes to weight and fat loss and might contribute to a reduction in fat-free mass.⁸

Weight loss and improvements in body composition are associated with sleep quality.⁹ Even a slight reduction in body weight contributes to improvements in sleep quality.¹⁰ Recent studies show that interventions with TRE lead to a reduction of at least 4% of total body weight.^11,12 Bohlman et al,¹³ in a recent systematic review, suggested that TRE does not worsen sleep quality, although the results were controversial. Nevertheless, the link between the effect of TRE on body composition and sleep parameters are unclear in the literature, as are the most appropriate time of food restriction and duration of the intervention to drive these effects. Therefore, our aim in conducting this systematic review was to investigate the effects of TRE on body composition and sleep parameters in adults.

METHODS

Study Type

A systematic review of the literature was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines¹⁴ and methodological recommendations of the Cochrane Collaboration.¹⁵ This review is registered in PROSPERO (registration no. CRD42024524598).

Review Question

The PICOS formulation detailed in Table 1 was adopted, from which the following research question was created and refined: Does restricting eating time have an effect on sleep parameters and body composition in adults?

Search Strategies

The MEDLINE/PubMed, SCOPUS, Web of Science (Clarivate), and BVS/Bireme literature databases were searched. From MEDLINE/PubMed, we searched on descriptors indicated by Medical Subject Headings and the Boolean operators “OR” and “AND”, as follows: (((((((Intermittent Fasting) OR (fasting)) OR (Time Restricted Eating)) OR (Eating)) OR (Time Restricted)) OR (Time Restricted Fasting OR Fasting, Time Restricted OR Restricted Fastings, Time OR Time Restricted Feeding OR Feeding, Time Restricted OR Time Restricted Feedings)) AND (“Sleep” OR Sleeping Habits OR Sleep Habits OR Habits, Sleep OR Sleep Habit OR Sleeping Habit OR Habit, Sleeping OR Habits, Sleeping)). The same search was carried out in the 4 databases from February to May 2024.

Eligibility Criteria

The eligible articles had to report on clinical intervention, controlled or uncontrolled studies, conducted with participants older than 18 years, with no gender restriction. The interventions had to control feeding time duration of the intervention, with or without a control group. Body composition could be assessed by any validated method, such as bioelectrical impedance, dual-energy X-ray absorptiometry, and magnetic resonance imaging. Sleep could be assessed by polysomnography, actigraphy, or validated sleep assessment questionnaires. The languages of publication were not delimited. The exclusion criteria were studies conducted with nonhuman models or literature reviews; those that included children, adolescents, and pregnant women; and those not controlling or restricting feeding time.

Procedures for Developing the Systematic Review

This systematic review was developed according to the following steps. (1) Two authors (B.A.S. and A.C.Q.) read the article titles and abstracts, excluding the ones not related to the research question and the duplicates. A third author (C.M.M.) reviewed this work and inconsistencies were solved by consensus. (2) Selected articles were read in full to identify the inclusion and exclusion criteria. Two authors performed this step independently (B.A.S. and A.C.Q.); divergences were resolved by consensus with a third author (C.M.M.). (3) Data extraction was performed by the first author (B.A.S.), checked by the second author (A.C.Q.), and organized in commercially available spreadsheet software. The data extracted were location and time of the study, study objectives, study design, sample characteristics, type of intervention, control group (if any), duration of the intervention, adherence to and side effects of the intervention, methods for assessing sleep, body composition and compliance to the intervention or diet, main results, and synthesis of findings.

The results are summarized descriptively or as percentages. Sleep and body composition results are presented as mean, mean SD, CIs in some cases, P values, and percentages.

Quality Assessment (Risk of Bias)

The risks of bias were assessed independently by 2 researchers (B.A.S. and C.M.M.), and the divergences were resolved by consensus including the third author (J.P.L.O.). The Cochrane Risk-of-Bias tool, version 2 (RoB2) was adopted. We used RoB2¹⁶ software to assess the randomized clinical trials, and Cochrane’s Risk of Bias in Nonrandomized Studies – of Interventions (ROBINS I)¹⁷ was used to assess the nonrandomized clinical trials.

According to RoB2,¹⁶ for cluster-randomized trials, the risk of bias is assessed by considering the randomization process, deviations from the intended interventions, missing outcome data, outcome measurements, and the selection of reported results. According to ROBINS I,¹⁷ the risk of bias is assessed by considering the factors confounding classification of interventions, selection of participants, deviations from intended interventions, missing data, measurements of outcomes, and selection of reported results. The overall risk-of-bias evaluation is subjective and decided among the research team. The risk of bias was defined as high risk, some concerns, or low risk on the basis of the majority of decisions from the 5 items in RoB2¹⁶ and of 7 items on Robins I.¹⁷

RESULTS

Literature Search

The initial search resulted in 1690 publications. After initial screening by title and abstract, 9 articles were duplicated, and 1645 were excluded for not meeting the eligibility criteria, resulting in 36 articles selected for a full reading. This step led to the exclusion of 25 studies: 14 did not test TRE and did not show the control of the eating-time window, 8 studies did not evaluate or describe sleep and body composition outcomes, 2 have not been finalized, and 1 couldn’t be acessed by the authors. After double-checking for exclusion and inclusion criteria, 11 studies were included in the present systematic review. Figure 1 shows the flowchart of the article selection process.

Studies Characteristics

Tables 2 and 3 list the data extracted from the included studies. Samples varied between 19 and 137 participants, aged between 18 and 71 years, with a predominance of female participants in 10 studies. Seven studies were performed in the United States, 2 in South Korea, 1 in Canada, and 1 in China. Seven were randomized controlled trials and 4 were single-arm clinical trials. Seven of the studies (58.3%) tested interventions of 8 hours of TRE. The duration of interventions was between 4 weeks and 12 months, with two studies lasting 4 weeks, three lasting 8 weeks, 3 lasting 12 weeks, 2 studies with 14 weeks’ duration, and, 1 with a long-term intervention of 12 months.

For body composition assessments, 5 studies (45.4%) used dual-energy X-ray absorptiometry, 5 used bioelectrical impedance, and 1 study used magnetic resonance imaging. For sleep evaluation, 8 studies (72.7%) used questionnaires, including the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index, Munich Chronotype Questionnaire, and Berlin Questionnaire. Two studies used questionnaires plus actigraphy, and 1 used only actigraphy.

Most of the studies monitored ad libitum food consumption using apps, daily adherence records, and daily food records. In their study, Kim and Song¹⁸ provided participants food bars with 20 g of protein to avoid muscle loss, despite not providing meals.

All studies observed reductions in body weight. Of the 11 studies, 9 observed reductions in total body fat and 2 reported reductions in visceral fat mass.^19,20 We note that the body composition data from the study conducted by Kirkham et al²¹ were presented in a manuscript published in 2022.²⁰ Ten studies reported baseline sleep data (the exception was the study by Jamshed et al²²) and all 11 reported an average sleep duration of 7 hours or longer, considered the minimum recommended amount per night.²³ All studies focused on sleep duration, in addition to other subjective sleep variables.

Effects of TRE on Body Composition and Sleep

All included studies evaluated body composition and sleep parameters. It is important to highlight the differences in intervention duration between studies, with most interventions lasting between 4 and 14 weeks and 1 study lasting 12 months.

Figure 2 provides a summary of the sleep and body composition results. All the studies observed a weight loss after intervention that varied between 0.94 and 7.6 kg. Nine studies (83%) reported reductions in body weight and body fat.^{18–20,24–29} The reductions in body fat ranged from 0.5 to 2.8 kg. Wilkinson et al¹⁹ and Zhang et al²⁸ also found reductions in visceral fat mass as estimated by bioelectrical impedance. Only 2 studies did not find any differences in body composition after TRE intervention.^22,30

Most studies evaluated sleep by questionnaires, and only 3 studies included actigraphy measurements; these studies did not report changes in sleep duration after TRE.^19,21,30 The studies of Wilkinson et al¹⁹ and Kirkham et al²⁰ showed reductions in fat mass. The studies of Jamshed et al (2022)²² and Manoogian et al³⁰ did not report any body composition changes besides weight loss.

The study samples described in the reviewed articles differed greatly although they were similar in terms of TRE intervention (8-10 hour TRE; 8-12 weeks’ duration). The participant samples in the studies of Wilkinson et al¹⁹ and Kirkham et al²⁰ were smaller and comprised individuals with obesity (n = 19 and n = 22, respectively) and both were noncontrolled studies. Manoogian et al³⁰ studied a larger sample of 137 men and women (70% with obesity; 40% male participants) who were 24-hour shift workers. In addition to a larger sample, this study had a control group that received nutritional advice for a Mediterranean diet. This is the only study included in this review that analyzed sleep duration objectively and was controlled. Nevertheless, no body composition changes were associated with sleep changes after TRE intervention. It is important to note that the study of Manoogian et al³⁰ included shift workers, a population usually not included in TRE interventions, due to circadian misalignment. Taken together, no studies, independently of weight loss or body composition changes, objectively observed changes in sleep duration after TRE interventions.

Most of the studies evaluated sleep subjectively using different questionnaires (eg, PSQI, Epworth Sleep Scale, Insomnia Severity Index, Berlin, Munich Chronotype Questionnaire), including the ones that used both questionnaires and actigraphy. From the studies that reported weight and fat loss after TRE, only 2 found changes in sleep parameters and these were subjective. Wilkinson et al¹⁹ reported an increase in the perception of restful sleep from 69.88% (SD  ± 25.61) of days at the start of the study to 88.16% (SD  ± 21.89) (P = .019) at the end of the intervention and a 35% reduction in the variance of waking time in the intervention group (from 3.42 hours to 2.21 hours). Steger et al²⁹ found reductions in sleep duration ± SD of 30 ± 13 minutes (P = .03), an increase in latency of 7 ± 3 min (P = .04), and a reduction in sleep efficiency of 2% ± 1% (P = .04) compared with the control group. No changes in sleep quality or sleep time, including sleep onset, sleep compensation, sleep inertia, or chronotype, were found. Six studies (55%) were notable for reporting changes in subjective sleep parameters even after weight and body composition changes.^18,24–28

Finally, 2 studies in which participants presented weight loss without changes in body composition reported divergent results regarding sleep parameters (evaluated subjectively). Manoogian et al³⁰ reported reductions in sleep disturbances at the end of the intervention (–0.16 [95% CI, –0.30 to –0.02]; P = .027) and reduced daytime sleepiness of standard of care group (–0.87 [95% CI, –1.49 to –0.25]; P = .007) and TRE (–1.10 [95% CI, –2.00 to –0.19]; P = .019) compared with baseline, although there were no significant differences between groups. In the Jamshed et al²² study of 90 adults with obesity, predominantly women, participating in a weight loss program, an 8-hour TRE for 14 weeks plus energy restriction resulted in no significant differences in sleep duration, bedtime, wake time, and sleep latency between groups, as assessed by PSQI.

The addition of calorie restriction to TRE would accelerate weight loss and body composition improvements. Steger et al²⁹ evaluated the effects of TRE on metabolic health, sleep, and mood in 36 volunteers with obesity who actually complied with the intervention (5 of 7 days). An intervention with 8-hour TRE (early TRE) and energy restriction (eTRE+ER) of 500 kcal below energy expenditure was carried out with the experimental group and a control group, with an eating time ≥12 hours and lasting 14 weeks. Data in the following are reported with ±SD. Assessments of body composition revealed that the eTRE+ER group lost 7.6 ± 1.0 kg (7.0% ± 0.9%; P < .001), which means an additional 3.7 ± 1.2 kg compared with the control group. The eTRE+ER intervention also resulted in decreased body fat by 2.8 ± 1.3 kg and trunk fat by an additional 1.6 ± 0.7 kg compared with the control group. There were no differences between the intervention and control groups in fat-free mass (mean –0.7 ± 0.6 kg; –1.2 ± 0.3 vs –1.8 ± 0.6 kg, respectively; P = .25), appendicular lean mass (–0.3 ± 0.4 kg; P = .42), and visceral fat (–0.1 ± 0.1; P = .37). There were no changes in sleep quality (0.2 ± 0.7; P = .79), sleep onset (8 ± 13 minutes; P = .51), sleep compensation (–22 ± 14 minutes; P = .16), sleep inertia (1 ± 3 minutes; P = .78), or chronotype (1 ± 16 minutes; P = .94) assessed by questionnaires. However, there was a reduction in sleep duration of 30 ± 13 minutes, an increase in latency of 7 ± 3 minutes and a reduction in sleep efficiency of 2% ± 1% in the TRE group compared with the control group.

In the aforementioned Jamshed et al²² study, the participants were divided into 2 groups: the described eTRE+ER group and the control eating schedule (CON)+ER group with a 12-hour eating window and energy restriction. The eTRE+ER group lost an additional 2.3 kg of body weight (95% CI, –3.7 to –0.9 kg; P = .002) compared with the CON+ER group. However, there were no significant differences in absolute fat loss (–1.4 kg [95% CI, –2.9 to 0.2]; P = .09), fat-free mass (–0.1 kg [95% CI, –0.9 to 0.7]; P = .75), trunk fat (–0.9 kg [95% CI, –1.8 to 0.1]; P = .07), visceral fat (–0.1 kg [95% CI, –0.2 to 0.1]; P = .37), or appendicular lean mass (–0.1 kg [95% CI, –0.6 to 0.5]; P = .78). No differences were found in sleep duration, bedtime, wake time, and sleep latency, as assessed by PSQI, between the groups.

Risk of Bias and Quality Assessment

Figure 3 shows the individual risk of bias according to ROBINS-I. Two studies were classified as moderate risk^18,21 and 3 as serious risk.^19,24,25  Figure 4 shows the individual risk of bias cluster-randomized trials according to RoB2. Four studies were classified as some concerns^22,27,28,30 and 2 studies as high risk.^26,29

DISCUSSION

In this systematic review, we investigated the effects of TRE on body composition and sleep parameters in adults. Eleven articles reporting on clinical trials were included and most of the studies tested 8-hour TRE interventions lasting 8 weeks or more except for 1 intervention of 4 weeks and 1 of a year intervention. The sample was composed predominantly of adult female participants with overweight or obesity. Nine studies, although they had methodological differences, found that TRE can contribute to reduction in total body fat, and perhaps in visceral fat mass, without changes in fat-free mass.

No sleep improvements were found when this outcome was objectively measured; however, improvements in sleep perception were found in 66% of the studies. Several potential confounders were identified among the study designs that could explain the lack of intervention effects on sleep parameters: (1) adherence and duration of the intervention; (2) age of the volunteers; (3) food control; (4) sleep characteristics of the volunteers and lack of standardized methods to measure sleep; and (5) absence of data. We discuss our findings based on these possible confounders, and the risk of bias is addressed.

Adherence and Duration of the Intervention

It would seem logical that prolonged fasting would be associated with lower adherence to the TRE intervention. In this review, most studies had an intervention of 8-hour of TRE or longer (10 hours was the maximum), and the durations of the interventions were predominantly of 8 or 12 weeks or longer. Adherence to the intervention was considered by authors as excellent, ranging from 80% to 98% (the average adherence was 6 days each week). Furthermore, adherence rates to longer fasting-period interventions (namely, 16 hours and 18 hours) also was high (eg, 80% in the Cienfuegos et al²⁶ study). Otherwise, Jefcoate et al³¹ demonstrated in a study with 16 participants a low adherence (63%) even with a short intervention duration (5 weeks) and fasting period of 14 h.

The shorter duration of the interventions, on the other hand, did not prove to be a facilitating factor for adherence. Moreover, it may have hindered better outcomes, such as more weight loss and more significant changes in body composition. Termannsen et al³² studied the feasibility of TRE and found, in a systematic review that included 28 studies, an adherence rate of 95% in studies lasting <12 weeks and 89% in studies of 12 weeks’ duration or longer. Thus, it is possible to say that TRE was well implemented in the analyzed studies and it is a feasible approach to reduce weight and fat mass; however, the body composition achieved by TRE was not always enough to contribute to sleep improvements. This might be because the observed changes in body weight and composition did not reach the minimum threshold of effect in weight loss (5%-10%) considered in the literature as perhaps necessary to observe benefits in sleep parameters.^33,34

Still, even when controlling for other barriers to treatment adherence, such as social events, work commitments, nighttime leisure activities, living conditions, and family life,³¹ the main bias regarding adherence to TRE related to its assessment. A significant portion of studies applied a TRE intervention but did not assess adherence to it,^24,35,36 or the evaluation method used was often quite subjective. This assessment, in most cases, occurred through apps, reports, or notes that are prone to forgetfulness and requiring a great deal of honesty and commitment from the participant. This makes it difficult to understand whether the results are due to the lack of patient adherence or the effect of the intervention itself.

Age of the Volunteers

In this review, the age range of the study participants was between 18 and 71 years, which could serve as a confounding factor when evaluating the proposed outcomes. With aging, a primary change that occurs is the body composition, characterized by an increase in body fat, particularly in the abdominal region and visceral organs, alongside a gradual decline in muscle mass after the age of 30 years.³⁷ In their review, Li et al³⁸ describe sleep changes in healthy aging characterized by reduction in sleep duration, difficulties in sleep maintenance, and less deep sleep. Therefore, the physiological differences between younger and older adults may affect the comparison of body composition and sleep outcomes throughout the analyzed studies. Additionally, younger adults may have a slightly reduced forgetfulness factor in adherence assessment.

Food Control

The isolated TRE provides autonomy to participants, allowing them to eat to satiety without any restrictions related to quality or quantity of food consumption. Cienfuegos et al²⁶ and Manoogian et al³⁰ demonstrated that regardless of dietary control, there was a reduction in energy intake among the groups with TRE of 6 hours, 8 hours, and 10 hours compared with the control group. Similar results were found in the systematic review conducted by Adafer et al,⁴ in which TRE led to a 20% reduction in caloric intake on average, without changing macronutrient distribution. Interestingly, Adafer et al⁴ reported that caloric restriction was described as unintentional by the participants, which might serve as a protection against cognitive restriction. However, it might be possible that observing changes in caloric intake have been hindered by the fact that few studies focused on assessing food consumption. Furthermore, studies on TRE have placed greater emphasis on metabolic outcomes, but there is a gap in current research evaluating its effects on food behavioral and dietary quality.

Caffeine consumption is another component of relevance in studies involving TRE intervention, particularly concerning sleep outcomes. In some of the reviewed studies,^{21,25,26,28,30} caffeine consumption, from non-energy drinks such as coffee, black tea, and soda, was allowed during the fasting period. The elevated consumption of caffeine might promote weight loss and increase fat oxidation.³⁹ However, most of the studies did not control the consumption of this component, with the exception of the Lin et al study,²⁷ which limited the intake to 2 non-energy drinks per day, and the Kirkham et al study,²¹ which allowed consumption from 8 am to 12 pm without quantity restriction. Indeed, when consumed in higher doses or close to bedtime, caffeine leads to reduced total sleep time and efficiency, and increased sleep latency.⁴⁰ All these factors probably impair sleep quality and, thus, compromise the observed effects of TRE on sleep parameters.

Sleep Assessment and Characteristics

Most of the studies included in this review used subjective methods to assess sleep, such as questionnaires; only 3 used actigraphy. Although subjective sleep assessment is a practical and suitable tool for clinical screening and large-scale studies, it lacks the precision of objective tools like polysomnography.⁴¹ Actigraphy is a method to assess sleep quality and quantity through movement assessment; it reflects sleep quality and duration from algorithms applied to raw motor activity data. It has been used to study nocturnal sleep and circadian rest/activity rhythm in different situations.⁴² A study comparing 3 different sleep assessment methods in patients with insomnia and fibromyalgia showed that actigraphy had more concordant values with polysomnography than the sleep diary, which is a subjective assessment method.⁴³

In addition, there was a greater focus only on the sleep duration variable in some studies. Other than sleep duration, improvements in sleep perception, such as the feeling of restorative sleep and sleep latency (the time spend between time lying down and sleep), were not explored in some studies. McStay et al,⁴⁴ for example, showed that sleep duration remained unchanged, but effects of intermittent fasting on sleep latency and efficiency were observed. This lack of standard of sleep variables between studies contributes to the different results found in the analyzed literature.

In studies where baseline data were provided, the duration of sleep in the samples was typically within the recommended range (ie, ∼7 hours). It is argued that there may be little utility in detecting improvements in sleep parameters among individuals who already have good sleep quality, especially when assessing the same variable, such as sleep duration. In addition, sleep was not the main outcome in the studies.

Absence of Data

The absence of baseline and postintervention data makes the analysis of the effects of the TRE intervention difficult. Two studies did not present baseline data, such as sleep duration; they only presented the difference between studied groups.

Risk of Bias

The risk of bias was assessed by the adequate Cochrane instruments according to the study design, that is, RoB2 was used to assess the 5 randomized controlled trials^{18,19,21,24,25} and we used the Robins I tool, specifically developed for nonrandomized trials, to assess risk of bias of the remaining studies. Three nonrandomized studies were considered high risk^19,24,25 and 2 of moderate risk^18,21; of the randomized control trials, 2 were considered at serious risk of bias^26,29 and 4 were considered of moderate risk.^22,27,28,30 The main justification for reaching the high-risk classification stems from the difficulty in blinding participants and researchers, which is a common issue in dietary intervention studies. In the study by Steger et al,²⁹ the lack of data in the results on the intervention group and the true value of the outcome was a significant risk of bias. Crossover trials in which only data from the first period are available should be considered at risk of bias, especially when investigators explicitly used a 2-phase strategy.

Intermittent Fasting vs TRE

Overall, intermittent fasting is a more intense approach than a TRE strategy. Intermittent fasting strategies most commonly include alternate-day fasting, which involves fasting for 24 hours every other day, and the 5:2 method, with 24-hour fasting twice a week and a very low-calorie diet consumed on 2 other days of the week.⁴⁵

Otherwise, TRE implies fasting only during the day, moving the last meal away from bedtime, when glucose metabolism is impaired.^46–48 Typically TRE interventions are designed to reduce the eating window to 8 hours per day or less. The literature shows evidence regarding the adverse effects on sleep of eating late and larger amounts of food.^49,50 Lopes et al⁵¹ showed that individuals diagnosed with obstructive sleep apnea who ate late had longer sleep latency, a higher Apnea Hypopnea Index, and a higher risk of poor sleep quality compared with early eaters. In a clinical trial, healthy individuals experienced a deterioration in sleep parameters on the night they consumed a high-fat, slow-digesting meal compared with an easier-to-digest meal.⁵² In this sense, the alignment of meals to the biological clock in association with a limited eating window should contribute to weight maintenance and might be a complementary strategy for long-term weight loss, taking turns with moderate energy-restricted diets.

CONCLUSION

Besides the theoretical implication of TRE effects on sleep quality, the lack of objective measures of sleep in response to a TRE intervention limits the results regarding this outcome. The findings from this systematic literature review suggest that TRE produces weight loss and changes in body composition, but its effects on sleep remain unclear, independent of body composition changes. Regardless of body composition changes, studies usually did not show changes in sleep measured by actigraphy; the perception of sleep, however, might change after the intervention.

It is difficult to establish solid conclusions from participants with a healthy sleep duration and with sleep assessment focused only on duration, without analyses of other sleep-quality parameters. However, these findings can provide valuable data for designing and formulating new well-founded studies. Clinical trials with sleep assessment using objective methods and including different sleep parameters are needed to elucidate the effect of TRE on sleep.

Acknowledgments

 

Author Contributions

B.A.S., C.M.M., A.C.Q.S., J.P.L.O. and M.L.A.F. collaborated on the design, writing, and final content of the manuscript, and all read and approved the manuscript.

Funding

This work was supported by the research support Foundation of Minas Gerais–Brazil (FAPEMIG; grant APQ 1748–21). B.A.S. received financial support from FAPEMIG and J.P.L.O. received financial support provided by Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes - process no 88887.966974/2024–00).

Conflicts of Interest

None declared.

References