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Effect of Calorie Restriction and Intermittent Fasting Regimens on Brain-Derived Neurotrophic Factor Levels and Cognitive Function in Humans: A Systematic Review.
Alkurd, R, Mahrous, L, Zeb, F, Khan, MA, Alhaj, H, Khraiwesh, HM, Faris, ME
Medicina (Kaunas, Lithuania). 2024;60(1)
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Brain-derived neurotrophic factor (BDNF) is a protein that plays a crucial role in brain development, cognition and metabolism. Intermittent fasting (IF) is a promising therapeutic strategy for managing metabolic disorders and improving cognitive function. Therefore, this systematic review of sixteen experimental and observational studies investigated the effect of IF on BDNF production and improvements in cognition through the BDNF pathway in healthy adults and people with metabolic disorders. Included studies focused on different IF regimens such as calorie restriction (CR), alternate-day fasting (ADF), time-restricted eating (TRE) and Ramadan model of intermittent fasting (RIF) Future, well-controlled, long-term, robust studies are required to assess the effect of different IF regimens on the production of BDNF and cognitive function in people with metabolic disorders, as the current research is inconclusive. However, healthcare professionals can use the review to understand the potential beneficial effects of IF on cognition and metabolic health in humans.
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.
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Effectiveness of an intermittent fasting diet versus regular diet on fat loss in overweight and obese middle-aged and elderly people without metabolic disease: a systematic review and meta-analysis of randomized controlled trials.
Yao, K, Su, H, Cui, K, Gao, Y, Xu, D, Wang, Q, Ha, Z, Zhang, T, Chen, S, Liu, T
The journal of nutrition, health & aging. 2024;28(3):100165
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People with obesity and overweight are at increased risk of developing metabolic diseases. Intermittent fasting is considered an effective non-pharmaceutical management strategy for reducing weight and body fat. This systematic review and meta-analysis included nine randomised controlled trials to evaluate the effectiveness of intermittent fasting on lipids, body composition, and body morphology in middle-aged and elderly people without metabolic diseases. Included studies used different intermittent fasting strategies such as alternate-day fasting (ADF), 5:2 fasting (2DW), time-restricted eating (TRF), and Ramadan fasting (FCR). The duration of intervention in the included studies ranged from six weeks to twelve weeks. This systematic review and meta-analysis found that intermittent fasting improved body weight, body mass index, fat mass, and triglycerides in adults over forty without metabolic diseases compared to a regular diet. Healthcare professionals can use the results of this study to understand that intermittent fasting could be an effective strategy for reducing fat mass and weight in middle-aged and elderly people without metabolic diseases. Further robust studies are needed to confirm the benefits of intermittent fasting due to the high variability between included studies.
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.
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Effect of Ramadan Fasting on Weight and Body Composition in Healthy Non-Athlete Adults: A Systematic Review and Meta-Analysis.
Fernando, HA, Zibellini, J, Harris, RA, Seimon, RV, Sainsbury, A
Nutrients. 2019;11(2)
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Ramadan is the Islamic tradition of fasting for one month from sunrise to sunset. Generally, Ramadan is known to impact weight. This systematic review and meta-analysis specifically evaluated the effects of Ramadan on both weight and body mass (fat mass and fat-free mass), pre and post fasting, and in the context of there being no attempt to influence physical activity or diet. The meta-analysis was conducted on 70 publications, 90 comparison groups and 2947 participants. Data was also extracted for diverse sub-groups such as overweight/obese, gender and geographical location. The results showed that Ramadan promoted a significant reduction in weight pre and post fasting across all participants, and that the greater the BMI prior to Ramadan fasting, the greater the weight loss. No significant differences were noted between genders. Weight loss was significant in the Middle East + North Africa, South Asia and South East Asia, but not in Westernized countries. Ramadan fasting promoted a transient reduction in fat mass as a percentage of weight, and absolute fat mass, but quickly returned to pre-fasting levels at follow-up 2-5 weeks later. A significant reduction in fat-free mass was also noted but 30% less than total fat mass. There was insufficient data to analysis the possible impact of physical activity. The authors conclude that Ramadan represents an opportunity for promoting weight and fat loss for people with overweight or obesity but requires strategies for long-term maintenance
Abstract
BACKGROUND Ramadan involves one month of fasting from sunrise to sunset. In this meta-analysis, we aimed to determine the effect of Ramadan fasting on weight and body composition. METHODS In May 2018, we searched six databases for publications that measured weight and body composition before and after Ramadan, and that did not attempt to influence physical activity or diet. RESULTS Data were collected from 70 publications (90 comparison groups, 2947 participants). There was a significant positive correlation between starting body mass index and weight lost during the fasting period. Consistently, there was a significant reduction in fat percentage between pre-Ramadan and post-Ramadan in people with overweight or obesity (-1.46 (95% confidence interval: -2.57 to -0.35) %, p = 0.010), but not in those of normal weight (-0.41 (-1.45 to 0.63) %, p = 0.436). Loss of fat-free mass was also significant between pre-Ramadan and post-Ramadan, but was about 30% less than loss of absolute fat mass. At 2⁻5 weeks after the end of Ramadan, there was a return towards, or to, pre-Ramadan measurements in weight and body composition. CONCLUSIONS Even with no advice on lifestyle changes, there are consistent-albeit transient-reductions in weight and fat mass with the Ramadan fast, especially in people with overweight or obesity.