A recent study published in JAMA Network Open has highlighted the potential of time-restricted eating (TRE) and calorie timing as effective strategies for weight management and improved metabolic health. This systematic review and meta-analysis of randomized clinical trials (RCTs) examined the impact of meal timing on body weight and metabolic outcomes.
The prevalence of obesity and overweight continues to rise globally, driven in part by unhealthy dietary habits and physical inactivity. These factors are linked to an increased risk of diabetes, cardiovascular disease, cancer, and premature mortality. Current estimates suggest that many individuals consume food for over 14 hours a day, often snacking late into the night, which exacerbates the risk of type 2 diabetes and negatively affects glycemic control. In contrast, intermittent fasting, which restricts eating to a six- to ten-hour window during the day, has gained popularity as a weight loss method.
Dietary modifications, particularly calorie restriction, are widely recognized as primary strategies for weight management. However, meal timing approaches—such as TRE, meal frequency reduction, and calorie distribution changes—are emerging as viable alternatives for those who struggle with traditional calorie monitoring.
The current study systematically reviewed published RCTs to assess the long-term effects of meal timing strategies on weight and metabolic outcomes in adults, regardless of their metabolic health status. Researchers conducted a comprehensive search of electronic databases for studies that examined within-day meal timing patterns over a minimum of 12 weeks and reported relevant anthropometric outcomes, such as body weight and body mass index (BMI).
The analysis ultimately included 29 RCTs with a total of 2,485 participants. However, the quality of the data was variable, with approximately 76% of the trials showing a high risk of bias.
The meta-analysis revealed that TRE significantly reduced body weight and BMI. Notably, participants with higher baseline BMI experienced greater weight loss compared to those with lower BMI. The most substantial weight reductions were observed in individuals consuming food within an eight-hour window or less each day. TRE was also linked to improvements in metabolic markers, including reductions in fasting blood glucose, glycated hemoglobin (HbA1c), and low-density lipoprotein (LDL) levels.
While lower meal frequency was associated with modest reductions in body weight and BMI, it did not significantly affect lean body mass or waist circumference. Additionally, meal frequency showed no clear impact on metabolic outcomes. Conversely, consuming a larger proportion of daily calories earlier in the day correlated with greater weight loss and lower BMI, but no significant associations were found for metabolic parameters.
Despite the encouraging findings, the study has several limitations. The subgroup analysis indicated that the weight-reducing effects of meal timing strategies were consistent, independent of the clinicians’ training levels. However, the generalizability of the results is limited, as most trials included participants from clinical settings with nutrition-trained clinicians. Furthermore, all studies on calorie distribution involved only female participants.
The overall quality of evidence was also a concern, given the risk of bias and inconsistencies across studies. The authors call for additional clinical trials with larger sample sizes, standardized intervention designs, and longer follow-up periods to clarify the health benefits of time-restricted eating.
Conclusion
The study concludes that meal timing strategies, particularly time-restricted eating, can lead to moderate reductions in body weight, BMI, and waist circumference when implemented for over 12 weeks. Additionally, TRE may help lower HbA1c and fasting glucose levels, suggesting its potential utility in diabetes management.
The rigid nature of traditional calorie counting is often cited as a barrier to adherence in weight loss programs. In contrast, time-restricted eating presents a more flexible and sustainable approach, offering healthcare providers an effective tool to support behavioral changes in overweight and obese adults.
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