The effects of time-restricted eating versus habitual diet on inflammatory cytokines and adipokines in the general adult population: a systematic review with meta-analysis

The influence of time-restricted eating/feeding on Alzheimer's biomarkers and gut microbiota

OBJECTIVES

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting approximately 55 million individuals globally. Diagnosis typically occurs in advanced stages, and there are limited options for reversing symptoms. Preventive strategies are, therefore, crucial. Time Restricted Eating (TRE) or Time Restricted Feeding (TRF) is one such strategy. Here we review recent research on AD and TRE/TRF in addition to AD biomarkers and gut microbiota.

METHODS

A comprehensive review of recent studies was conducted to assess the impact of TRE/TRF on AD-related outcomes. This includes the analysis of how TRE/TRF influences circadian rhythms, beta-amyloid 42 (Aß42), pro-inflammatory cytokines levels, and gut microbiota composition.

RESULTS

TRE/TRF impacts circadian rhythms and can influence cognitive performance as observed in AD. It lowers beta-amyloid 42 deposition in the brain, a key AD biomarker, and reduces pro-ininflammatory cytokines. The gut microbiome has emerged as a modifiable factor in AD treatment. TRE/TRF changes the structure and composition of the gut microbiota, leading to increased diversity and a decrease in harmful bacteria.

DISCUSSION

These findings underscore the potential of TRE/TRF as a preventive strategy for AD. By reducing Aß42 plaques, modulating pro-inflammatory cytokines, and altering gut microbiota composition, TRE/TRF may slow the progression of AD. Further research is needed to confirm these effects and to understand the mechanisms involved. This review highlights TRE/TRF as a promising non-pharmacological intervention in the fight against AD.

The effect of time-restricted eating combined with exercise on body composition and metabolic health: a systematic review and meta-analysis

BACKGROUND

Time-restricted eating (TRE) has been increasingly popular, but its benefits in combination with exercise still need to be determined.

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the efficacy of TRE combined with exercise compared with control diet with exercise in improving the body composition and metabolic health of adults.

METHODS

Five electronic databases were searched for relevant studies. Randomized controlled trials (RCT) examining the effect of TRE combined with exercise on body composition and metabolic health in adults were included. All results in our meta-analysis were described as mean difference (MD) with 95% confidence interval (Cl). Study quality was assessed using the revised Cochrane Risk of Bias Tool and Grading of Recommendations Assessment, Development, and Evaluation assessment.

RESULTS

In total, 19 RCTs comprising 568 participants were included in this systematic review and meta-analysis. TRE combined with exercise likely reduced the participants' body mass (MD = -1.86 kg, 95% CI [-2.75, -0.97]) and fat mass (MD = -1.52 kg, 95% CI [-2.07, -0.97]) when compared to the control diet with exercise. In terms of metabolic health, the TRE combined with the exercise group likely reduced triglycerides (MD = -13.38 mg/dl, 95% CI [-21.22, -5.54]) and may result in a reduction in low-density lipoprotein (MD = -8.52 mg/dl, 95% CI [-11.72, -5.33]) and a large reduction in leptin (MD -0.67 ng/ml; 95%CI [-1.02, -0.33]). However, TRE plus exercise exhibited no additional benefit on the glucose profile, including fasting glucose and insulin, and other lipid profiles, including total cholesterol and high-density lipoprotein levels, compared with the control group.

CONCLUSIONS

Combining TRE with exercise may be more effective in reducing body weight and fat mass and improving lipid profile than control diet with exercise. Implementing this approach may benefit individuals aiming to achieve weight loss and enhance their metabolic well-being. REGISTRY AND REGISTRY NUMBER FOR SYSTEMATIC REVIEWS OR META-ANALYSES: CRD42022353834.

Eating Frequency, Timing, and Duration in Relation to Cognitive Performance and Alzheimer Disease Biomarkers in Adults

BACKGROUND

The potential association between temporal dimensions of eating and cognition/cognitive declines has been poorly investigated so far.

OBJECTIVES

The aim of this study was to examine relationships among eating frequency, timing and time window, and cognitive performance and novel Alzheimer disease (AD) biomarkers in cognitively healthy and mildly cognitively impaired middle-aged and older adults.

METHODS

Cross-sectional data were derived from the Aiginition Longitudinal Biomarker Investigation of Neurodegeneration (ALBION) cohort study, including people aged 40 y or older who have a positive family history of cognitive disorder or cognition-related concerns. Cognitive performance was assessed by a battery of neuropsychological tests. Amyloid β (Αβ42), a biomarker of AD-related pathology, was measured in cerebrospinal fluid. Eating frequency, timing, and the eating time window between the first and the last meal were estimated using time-related information recorded in four 24-h recalls.

RESULTS

Study participants had, on average, 5.3 ± 1.2 eating episodes per day, consumed at 8:20 ± 1.3 and 21:14 ± 1.3 h their first and their last eating episode, respectively, while their eating time window was 12.9 ± 1.6 h. Eating frequency, but not eating time window, was positively associated with global cognition, executive and language performance even after controlling for age, sex, education, BMI, and Mediterranean diet. Increasing eating frequency by 1 eating episode per day was associated with 0.169 higher global z-score. Furthermore, compared with ≤4, having 5-6 or >6 eating episodes per day was associated with better global and memory z-scores. Time of last eating episode was also positively associated with language performance. No associations were detected among eating frequency, timing and window, and AD pathology.

CONCLUSIONS

An eating pattern characterized by less frequent eating and/or by earlier times is present in individuals with worse cognitive performance. Our results shed light on the relevance of temporal eating patterns as potential early markers of behavioral or metabolic changes related to AD pathology.

Intermittent fasting and health outcomes: an umbrella review of systematic reviews and meta-analyses of randomised controlled trials

Background

Benefits of Intermittent fasting (IF) on health-related outcomes have been found in a range of randomised controlled trials (RCTs). Our umbrella review aimed to systematically analyze and synthesize the available causal evidence on IF and its impact on specific health-related outcomes while evaluating its evidence quality.

Methods

We comprehensively searched the PubMed, Embase, Web of Science, and Cochrane databases (from inception up to 8 January 2024) to identify related systematic reviews and meta-analyses of RCTs investigating the association between IF and human health outcomes. We recalculated the effect sizes for each meta-analysis as mean difference (MD) or standardized mean difference (SMD) with corresponding 95% confidence intervals (CIs). Subgroup analyses were performed for populations based on three specific status: diabetes, overweight or obesity, and metabolic syndrome. The quality of systematic reviews was evaluated using A Measurement Tool to Assess Systematic Reviews (AMSTAR), and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. This study is registered with PROSPERO (CRD42023382004).

Findings

A total of 351 associations from 23 meta-analyses with 34 health outcomes were included in the study. A wide range of outcomes were investigated, including anthropometric measures (n = 155), lipid profiles (n = 83), glycemic profiles (n = 57), circulatory system index (n = 41), appetite (n = 9), and others (n = 6). Twenty-one (91%) meta-analyses with 346 associations were rated as high confidence according to the AMSTAR criteria. The summary effects estimates were significant at p < 0.05 in 103 associations, of which 10 (10%) were supported by high certainty of evidence according to GRADE. Specifically, compared with non-intervention diet in adults with overweight or obesity, IF reduced waist circumference (WC) (MD = -1.02 cm; 95% CI: -1.99 to -0.06; p = 0.038), fat mass (MD = -0.72 kg; 95% CI: -1.32 to -0.12; p = 0.019), fasting insulin (SMD = -0.21; 95% CI: -0.40 to -0.02; p = 0.030), low-density lipoprotein cholesterol (LDL-C) (SMD = -0.20; 95% CI: -0.38 to -0.02; p = 0.027), total cholesterol (TC) (SMD = -0.29; 95% CI: -0.48 to -0.10; p = 0.003), and triacylglycerols (TG) (SMD = -0.23; 95% CI: -0.39 to -0.06; p = 0.007), but increased fat free mass (FFM) (MD = 0.98 kg; 95% CI: 0.18-1.78; p = 0.016). Of note, compared with the non-intervention diet, modified alternate-day fasting (MADF) reduced fat mass (MD = -0.70 kg; 95% CI: -1.38 to -0.02; p = 0.044). In people with overweight or obesity, and type 2 diabetes, IF increases high-density lipoprotein cholesterol (HDL-C) levels compared to continuous energy restriction (CER) (MD = 0.03 mmol/L; 95% CI: 0.01-0.05; p = 0.010). However, IF was less effective at reducing systolic blood pressure (SBP) than a CER diet in adults with overweight or obesity (SMD = 0.21; 95% CI: 0.05-0.36; p = 0.008).

Interpretation

Our findings suggest that IF may have beneficial effects on a range of health outcomes for adults with overweight or obesity, compared to CER or non-intervention diet. Specifically, IF may decreased WC, fat mass, LDL-C, TG, TC, fasting insulin, and SBP, while increasing HDL-C and FFM. Notably, it is worth noting that the SBP lowering effect of IF appears to be weaker than that of CER.

Funding

This work was supported by the National Key Research and Development Program of China (Q-JW), the Natural Science Foundation of China (Q-JW and T-TG), Outstanding Scientific Fund of Shengjing Hospital of China Medical University (Q-JW), and 345 Talent Project of Shengjing Hospital of China Medical University (T-TG).

Time-Restricted Eating and Bone Health: A Systematic Review with Meta-Analysis

Time-restricted eating (TRE) has emerged as a dietary strategy that restricts food consumption to a specific time window and is commonly applied to facilitate weight loss. The benefits of TRE on adipose tissue have been evidenced in human trials and animal models; however, its impact on bone tissue remains unclear. To systematically synthesize and examine the evidence on the impact of TRE on bone health (bone mineral content (BMC), bone mineral density (BMD), and bone turnover factors), PubMed, Scopus, Cochrane CENTRAL, and Web of Science databases were systematically explored from inception to 1 October 2023 searching for randomized controlled trials (RCTs) aimed at determining the effects of TRE on bone health in adults (≥18 years). The Cochrane Handbook and the PRISMA recommendations were followed. A total of seven RCTs involving 313 participants (19 to 68 years) were included, with an average length of 10.5 weeks (range: 4 to 24 weeks). Despite the significant weight loss reported in five out of seven studies when compared to the control, our meta-analysis showed no significant difference in BMD (g/cm2) between groups (MD = -0.009, 95% CI: -0.026 to 0.009, p = 0.328; I2 = 0%). BMC and bone turnover markers between TRE interventions and control conditions were not meta-analyzed because of scarcity of studies (less than five). Despite its short-term benefits on cardiometabolic health, TRE did not show detrimental effects on bone health outcomes compared to those in the control group. Nevertheless, caution should be taken when interpreting our results due to the scarcity of RCTs adequately powered to assess changes in bone outcomes.

Effectiveness of Time-Restricted Eating with Caloric Restriction vs. Caloric Restriction for Weight Loss and Health: Meta-Analysis

Time-restricted eating (TRE) is an increasingly popular dietary strategy for weight loss. Recent studies suggest that combining TRE with caloric restriction (CR) may have more favorable effects on both physical and biochemical aspects when compared with CR alone. Therefore, we performed a meta-analysis to compare the effects of TRE with CR vs. CR alone on anthropometric and biochemical measures in overweight or obese adults. We reviewed articles from PubMed, Web of science, EMBASE, and the Cochrane Library published before 25 May 2023. The meta-analysis incorporated data from seven randomized controlled trials of nine interventions, with a total of 231 participants in the TRE with CR group and 227 participants in the CR-only group. Data were analyzed using RewMan version 5.4.1. All results in our meta-analysis were described as mean difference (MD) with 95% confidence interval (Cl). Results showed that TRE with CR compared to CR alone resulted in significantly greater reductions in body weight (MD: -2.11 kg, 95% CI: -2.68 kg to -1.54 kg, p = < 0.00001, I2 = 42%), body fat mass (MD: -0.75 kg, 95% CI: -1.35 kg to -0.16 kg, p = 0.01; I2 = 0%), and waist circumference (MD: -1.27 cm, 95% CI: -2.36 cm to -0.19 cm, p = 0.02, I2 = 0%), while no additional impact of TRE in combination with CR in comparison to CR on serum biochemical parameters were found. Our results suggest that the improvement in biochemical parameters are mainly caused by CR, while improvements in anthropometric parameters are further enhanced by TRE.