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11th August 2022
Early time-restricted eating (eTRE) in combination with a reduction of energy intake is more effective for weight loss in comparison to a similar reduced intake of energy but where feeding occurs over a period of 12 hours or more according to the findings of a randomised trial by US researchers.
Caloric restriction whilst maintaining adequate nutritional intake, can extend both lifespan and delay the onset of age-related disorders in monkeys, indicating that this approach would be of value to human health. Moreover, in a randomised trial in humans, a 6-month period of calorie restriction (roughly 12% over 2 years) concluded that 2 biomarkers of longevity (fasting insulin level and body temperature) are decreased by prolonged calorie restriction in humans. An alternative strategy to calorie restriction is intermittent fasting (IF) and has become popular in recent years as a means of weight loss although the benefits of IF compared to calorie restriction are still uncertain. Evidence from a 50-week randomised trial, suggested that there was no appreciable difference in outcomes between IF and continuous calorie restriction. But what if individuals practiced a form of IF and simultaneously reduced their calorie intake? Might this approach be easier to implement and increase weight loss among obese individuals? This was the objective of the current study in which researchers examined the value of ‘early time-restricted eating’ (between 7 am and 3 pm) in combination with a reduced energy diet. This approach was compared to one in which there was a similar reduced energy intake but where food intake was spread over a 12-hour or longer period. Participants were equally randomised to either eTRE or the control group and which the researchers said was designed to mimic typical US median meal timing habits. In both groups, participants reduced their energy intake by 500 kcal/day below their measured resting energy expenditure, measured by indirect calorimetry. In addition, all participants received counselling from a registered dietitian and were asked to exercise for 75 to 150 minutes per week.
The co-primary outcomes were weight and fat loss, whereas secondary outcomes were fasting cardiometabolic risk factors e.g., blood pressure, fasting glucose, insulin levels.
Early time-restricted eating and weight loss
A total of 90 participants with a mean age of 43 years (80% female) and mean body mass index (BMI) or 39.6, were recruited and equally randomised to eTRE or control arms.
The eTRE group lost a mean of 6.3 kg compared to a mean of 4 kg for the control group and this mean difference of 2.3 kg was statistically significant (p = 0.002). In contrast, there was no significant difference in fat loss (mean difference = -1.4, p = 0.09). Furthermore, there were no differences in trunk or visceral fat or waist circumferences. While eTRE did not significantly reduce systolic blood pressure, the difference in mean diastolic pressure was significant (mean difference = – 4 mmHg, p = 0.04).
The authors concluded that eTRE was more effective as a weight loss strategy in conjunction with energy restriction compared to eating over a 12-hour window.
Jamshed H et al. Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial JAMA Intern Med 2022