Time Restricting Eating Boosts Weight Loss when added to diet and exercise: JAMA

Birmingham: Researchers at University of Alabama at Birmingham have found in a a randomized trial that in addition to diet and exercise, time restricted eating within an 8-hour window helped people with obesity lose weight.

Further for obese individuals, practice of time-restricted eating by having food early in the day is more effective for losing weight and improving diastolic blood pressure and mood than eating after 12 or more hours of fasting.

The findings of a 14-week randomized clinical weight-loss trial have been published in the JAMA Internal Medicine.

Intermittent fasting (IF) is the practice of switching between fasting and eating on a regular schedule. Recently, IF has been promoted for losing weight and body fat. One form of intermittent fasting that is particularly promising is time-restricted eating (TRE), which is eating within a consistent window of 10 hours or less and fasting for the rest of the day. Studies have shown that adults who adhere to TRE, typically lose 1% to 4% of their body weight within several weeks. Further, TRE increases fat oxidation and can improve cardiometabolic end points, such as insulin sensitivity and blood pressure, even when calorie intake is matched to the control group. It is unclear how effective intermittent fasting is for losing weight and body fat, and the effects may depend on the timing of the eating window.

Jamshed H, the University of Alabama at Birmingham and his team initiated a study to determine whether practising TRE by eating early in the day (eTRE) is more effective for weight loss, fat loss, and cardiometabolic health than eating over 12 or more hours. The study was a 14-week, parallel-arm, randomized clinical trial conducted between August 2018 and April 2020.

Researchers included 90 adults aged 25 to 75 years with obesity who received weight-loss treatment for the study. All participants were randomized to eTRE plus ER (8-hour eating window from 7:00 to 15:00) or control eating (CON) plus ER (≥12-hour window). The eTRE+ER group adhered 6.0 (0.8) days per week. The co-primary outcomes were weight loss and fat loss. Secondary outcomes included blood pressure, heart rate, glucose levels, insulin levels, and plasma lipid levels.

Key findings of the study,

• The eTRE+ER intervention was more effective for losing weight (−2.3 kg; P = .002) but did not affect body fat (−1.4 kg; P = .09) or the ratio of fat loss to weight loss (−4.2%; P = .43).

• The effects of eTRE+ER were equivalent to reducing calorie intake by an additional 214 kcal/d.

• The eTRE+ER intervention also improved diastolic blood pressure (−4 mm Hg; P = .04) and mood disturbances, including fatigue-inertia, vigour-activity, and depression-dejection.

• All other cardiometabolic risk factors, food intake, physical activity, and sleep outcomes were similar between groups.

• In a secondary analysis of 59 completers, eTRE+ER was also more effective for losing body fat and trunk fat than CON+ER.

The authors conclude that eTRE is more effective for losing weight and lowering diastolic blood pressure than eating over 12 or more hours and eTRE intervention may be an effective treatment for both obesity and hypertension. eTRE also improves mood by decreasing fatigue and feelings of depression-dejection and increasing vigour. However, eTRE did not affect most fasting cardiometabolic risk factors in the main intention-to-treat analysis.

Jamshed H, Steger FL, Bryan DR, 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. Published online August 08, 2022. doi:10.1001/jamainternmed.2022.3050