Abstract

Background: The potential positive interaction between intermittent fasting (IF) and brain-derived neurotrophic factor (BDNF) on cognitive function has been widely discussed. This systematic review tried to assess the efficacy of interventions with different IF regimens on BDNF levels and their association with cognitive functions in humans. Interventions with different forms of IF such as caloric restriction (CR), alternate-day fasting (ADF), time-restricted eating (TRE), and the Ramadan model of intermittent fasting (RIF) were targeted. Methods: A systematic review was conducted for experimental and observational studies on healthy people and patients with diseases published in EMBASE, Scopus, PubMed, and Google Scholar databases from January 2000 to December 2023. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statements (PRISMA) for writing this review. Results: Sixteen research works conducted on healthy people and patients with metabolic disorders met the inclusion criteria for this systematic review. Five studies showed a significant increase in BDNF after the intervention, while five studies reported a significant decrease in BDNF levels, and the other six studies showed no significant changes in BDNF levels due to IF regimens. Moreover, five studies examined the RIF protocol, of which, three studies showed a significant reduction, while two showed a significant increase in BDNF levels, along with an improvement in cognitive function after RIF. Conclusions: The current findings suggest that IF has varying effects on BDNF levels and cognitive functions in healthy, overweight/obese individuals and patients with metabolic conditions. However, few human studies have shown that IF increases BDNF levels, with controversial results. In humans, IF has yet to be fully investigated in terms of its long-term effect on BDNF and cognitive functions. Large-scale, well-controlled studies with high-quality data are warranted to elucidate the impact of the IF regimens on BDNF levels and cognitive functions.

Abstract

AIMS: To evaluate the effect of an intensive lifestyle intervention (ILI) on the structural and functional cardiac substrate of atrial fibrillation (AF) in overweight or obese people with metabolic syndrome (Mets). METHODS AND RESULTS Participants of the PREvención con DIeta MEDiterranea-Plus trial (n = 6874) were randomized 1:1 to an ILI programme based on an energy-reduced Mediterranean diet, increased physical activity, and cognitive-behavioural weight management or to a control intervention of low-intensity dietary advice. A core echocardiography lab evaluated left atrial (LA) strain, function, and volumes in 534 participants at baseline, 3-year, and 5-year follow-ups. Mixed models were used to evaluate the effect of the ILI on LA structure and function. In the subsample, the baseline mean age was 65 years [standard deviation (SD) 5 years], and 40% of the participants were women. The mean weight change after 5 years was -3.9 kg (SD 5.3 kg) in the ILI group and -0.3 kg (SD 5.1 kg) in the control group. Over the 5-year period, both groups experienced a worsening of LA structure and function, with increases in LA volumes and stiffness index and decreases in LA longitudinal strain, LA function index, and LA emptying fraction over time. Changes in the ILI and control groups were not significantly different for any of the primary outcomes {LA emptying fraction: -0.95% [95% confidence interval (CI) -0.93, -0.98] in the control group, -0.97% [95% CI -0.94, -1.00] in the ILI group, Pbetween groups = 0.80; LA longitudinal strain: 0.82% [95% CI 0.79, 0.85] in the control group, 0.85% [95% CI 0.82, 0.89] in the ILI group, Pbetween groups = 0.24} or any of the secondary outcomes. CONCLUSION In overweight or obese people with Mets, an ILI had no impact on the underlying structural and functional LA substrate measurements associated with AF risk. This study evaluated whether an intervention-modifying lifestyle had an effect on the parts of the heart involved in the development of atrial fibrillation (AF), a common problem of the heart rhythm. This intervention was implemented in people who had excessive body weight and the metabolic syndrome (Mets), which is a combination of several cardiovascular risk factors. The lifestyle intervention included promoting a Mediterranean diet low in calories and increasing exercise to facilitate weight loss, and this intervention was compared with a control intervention to follow a healthy diet. We performed repeated studies of the heart structure and function with imaging over a period of 5 years. During the 5 years of the study, both study groups (intervention and control) showed changes in their heart consistent with ageing. However, these changes were not different in those who were receiving the lifestyle intervention. Also, participants who lost more weight, adhered better to the study diet, or did more physical activity, overall did not show any differences in their heart compared with those who did not achieve their lifestyle goals.In conclusion, a lifestyle intervention focusing on weight loss, better diet, and more exercise was not effective in improving parts of the heart potentially involved with the risk of AF.In people with metabolic syndrome, a weight control lifestyle intervention, based on an energy-reduced Mediterranean diet and physical activity, had no effect on the structural and functional cardiac substrate of atrial fibrillation.

Abstract

OBJECTIVE As the number of adults aged over 40 with obesity increases dramatically, intermittent fasting interventions (IF) may help them to lose fat and weight. This systematic review investigated the most recent research on the effects of intermittent fasting and a regular diet on body composition and lipids in adults aged over 40 with obesity without the metabolic disease. DATA SOURCES Randomized controlled trials (RCTs) on IF on adults aged over 40 with obesity were retrieved from PubMed, Web of Science, EBSCO, China Knowledge Network (CNKI), VIP database, Wanfang database with the experimental group using IF and the control group using a regular diet. Revman was used for meta-analysis. Effect sizes are expressed as weighted mean differences (WMD) and 95% confidence intervals (CI). STUDY SELECTION A total of 9 articles of randomised controlled trials that met the requirements were screened for inclusion. Studies typically lasted 2-6 weeks. The experimental population was aged 42-66 years, with a BMI range of 25.7-35 kg/m2. SYNTHESIS A total of 9 RCTs were included. meta-analysis showed that body weight (MD: -2.05 kg; 95% CI (-3.84, -0.27); p = 0.02), BMI (MD: -0.73 kg/m2; 95% CI (-1.05, -0.41); p < 0.001), fat mass (MD: -2.14 kg; 95% CI (-3.81, 0.47); p = 0.01), and TG (MD = -0.32 mmol/L, 95% CI (-0.50, -0.15, p < 0.001) were significantly lower in the experimental group than in the control group. No significant reduction in lean body mass (MD: -0.31 kg; 95% CI (-0.96, 0.34); p = 0.35). CONCLUSION IF had a reduction in body weight, BMI, fat mass, and TG in adults aged over 40 with obesity without metabolic disease compared to RD, and IF did not cause a significant decrease in lean body mass, which suggests healthy and effective fat loss. However, more long-term and high-quality trials are needed to reach definitive conclusions.