A recent randomized crossover trial presented at the Annual Meeting of The European Association for the Study of Diabetes (EASD) in Madrid has revealed that limiting eating to an eight-hour window significantly improves blood glucose control in prediabetic adults. The study, conducted by Dr. Kelly Bowden Davies and her team from Manchester Metropolitan University, indicates that this improvement occurs regardless of whether the eight-hour window is set earlier or later in the day.
Dr. Bowden Davies noted, “Our study demonstrates that an eight-hour eating window markedly enhances the time spent within the normal blood glucose range and minimizes blood glucose fluctuations. Notably, shifting the timing of this eight-hour period does not offer additional benefits.” The research underscores that the improvements are attributable to the 16-hour fasting period rather than the timing of eating or changes in energy intake. Importantly, the benefits of time-restricted eating (TRE) can be observed within just three days.
The trial builds on previous research suggesting that TRE—restricting the timing of food intake rather than the type or amount of food—can improve insulin sensitivity and glycated hemoglobin (HbA1c) levels in individuals at risk of type 2 diabetes. However, previous studies had not clearly established the effect of TRE on glycemic variability (fluctuations in blood glucose levels) or whether reduced energy intake was the primary factor behind observed improvements.
To address these gaps, the researchers conducted their study with participants in a state of energy balance, ensuring that energy intake matched energy expenditure. They compared the effects of an early time-restricted eating (ETRE) window (8:00 AM to 4:00 PM) and a late time-restricted eating (LTRE) window (12:00 PM to 8:00 PM) against a habitual eating pattern extending over more than 14 hours per day. The study involved 15 sedentary individuals with an average age of 52 years and a BMI of 28 kg/m².
During the TRE periods, participants followed a eucaloric standardized diet (50% carbohydrates, 30% fat, and 20% protein), while during habitual eating conditions, they followed their usual diet. Continuous glucose monitoring assessed the daily time spent in euglycemia (normal blood glucose levels) and various markers of glycemic variability, including mean absolute glucose (MAG), coefficient of variation (CV), and mean amplitude of glucose excursions (MAGE).
The results revealed that TRE significantly increased the time spent within the normal blood glucose range by an average of 3.3% compared to habitual eating. Additionally, TRE reduced glycemic variability, with reductions in MAG by 0.6 mmol/l, CV by 2.6%, and MAGE by 0.4 mmol/l. Importantly, no significant differences in glycemic control were observed between the ETRE and LTRE regimens.
Dr. Bowden Davies concluded, “Our findings suggest that focusing on the timing of food intake rather than calorie counting could offer a practical approach to improving blood sugar control in prediabetic individuals. This method shows promise and warrants further investigation in larger, long-term studies.”
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