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. 2022;182(9):953-962.
To explore the effect of time-restricted eating in comparison to consuming food over a period of more than 12 hours to determine which is more effective for fat loss, weight reduction, and cardiometabolic health
The dietary intervention of time-restricted eating is more effective for weight reduction, improvement in diastolic blood pressure, and mood than eating during a window of more than 12 hours daily.
A parallel-arm, randomized, controlled trial of 14 weeks' duration
Participants with obesity aged 25 to 75 years (mean age 43) were recruited into a trial for weight-loss treatment at the Weight Loss Medicine Clinic of the University of Alabama at Birmingham Hospital (UAB).
A total of 656 people were screened, and 90 participants were enrolled in the trial; 72 of the participants were female (80%), and 18 were male. Participants’ ethnicities included Hispanic 2%, non-Hispanic 94% (specifically, Asian 2%, Black 33%, and White 62%), and 3% who reported unknown.
Inclusion criteria consisted of participants having a body mass index (BMI) between 30 to 60 with no history of diabetes or other unstable medical conditions or an assessment of cardiometabolic risk factors.
A weight-loss treatment with participants randomized into 2 groups and assigned an eating schedule of a hypocaloric diet for 6 days per week. The groups consisted of: a group with early time-restricted eating plus energy restriction (eTRE+ER; based on an 8-hour eating window from 7:00 a.m. to 3:00 p.m.) and a group with a controlled-eating schedule plus ER (CON+ER) (≥12-hour window).
Study Parameters Assessed
Participants received weight-loss counseling from a dietitian at weeks 0, 2, 6, and 10. A dual x-ray absorptiometry (DEXA) was used to measure body composition every 2 weeks. Fat loss was measured based on the ratio comparing fat loss to weight loss and by fat-mass difference. Standard procedures were used to measure fasting blood pressure, homeostatic model beta-cell function, insulin resistance, plasma lipid levels, and hemoglobin A1c.
Additionally, investigators assessed adherence to eating windows via surveys. They used food records to measure composition of macronutrients and energy intake, followed by a post hoc analysis. The study employed several questionnaires to assess mood, sleep, physical activity, and satisfaction with eating times.
The primary outcomes were fat loss and weight loss. Secondary outcomes were based on cardiometabolic risk factors such as heart rate, blood pressure, glucose levels, hemoglobin A1c, and plasma lipid levels. Additional outcomes measured included satisfaction, adherence, physical activity, sleep, and mood.
The eTRE+ER group adhered to an eating schedule of 6 days per week (0.8), and the CON+ER group to a schedule of 6.3 days per week (0.8) with P=0.03.
Both groups had clinically significant weight loss (for the eTRE+ER group, –6.3 kg [-5.7%; 95% CI, –7.4 to –5.2 kg; P<0.001] and for the CON+ER group, – 4.0 kg [-4.2%; 95% CI, –5.1 to –2.9 kg; P< 0.001).
The eTRE+ER group achieved a higher weight loss total of 2.3 kg (95% CI, –3.7 to –0.9 kg, P=0.002), making it more effective for losing weight.
Neither group showed significant effects on body fat loss (–1.4 kg; 95% CI, –2.9 to 0.2 kg; P=0.09) or the ratio of fat loss to weight loss (n=41; –4.2%; 95% CI, –14.9 to 6.5%; P=0.43).
In a secondary analysis, eTRE+ER was more effective than CON+ER for the primary outcomes of losing weight (–2.3 kg; 95% CI, –3.9 to –0.7 kg, P=0.006), body fat (–1.8 kg; 95% CI, 3.6 to 0.0 kg; P=0.047), and trunk fat (–1.2 kg; 95% CI, –2.2 to –0.1 kg; P=0.03).
The eTRE+ER group had a significant reduction in diastolic blood pressure (–4 mmHg; 95% CI, –8 to 0 mmHg; P=0.04) compared to the CON+ER group. Furthermore, the eTRE+ER group had a significant reduction in caloric intake, with an additional 214 kcal/d cut (95% CI, –416 to –12 kcal/d; P=0.04) relative to CON+ER.
Lastly, eTRE+ER was more effective at decreasing mood disturbance and improving mood in the following subcategories of vigor-activity, fatigue-inertia, and depression-dejection. Both groups had similar food intake, cardiometabolic risk factors, physical activity, and sleep outcomes.
The study was approved by the Institutional Review Board of UAB and supported by grants from the National Center for Advancing Translational Sciences of the National Institutes of Health (NIH), the National Institute of Diabetes and Digestive and Kidney Diseases, Nutrition Obesity Research Center, and the Diabetes Research Center. One of the study's authors, Corby K Martin, invented the technology for the app used to assess food intake in this study, and the center where this study was conducted has interest in the intellectual property.
Practice Implications & Limitations
Cardiovascular disease (CVD) contributes to serious health-related issues worldwide. It is the leading cause of morbidity and mortality, affecting millions of people every year.1 In the United States, 2 in 3 adults are overweight, and 1 in 3 are obese.2 Obesity is associated with excessive body fat, which increases insulin resistance, blood lipids, and systemic inflammation, amplifying the risk of developing CVD, type 2 diabetes, and insulin resistance.3 Diet, as well as other modifiable lifestyle factors, has become an integral factor in reducing the burden of CVD.4 Dietary choices and poor eating habits have been linked to cardiometabolic risk factors for CVD, including high total cholesterol, increased blood pressure, and elevated BMI.3
Time-restricted eating (TRE) has been found to lower CVD and increase weight loss by allowing individuals to eat during a limited time schedule, preventing strain on the circadian system by altered eating patterns.3 TRE has been associated with improved CVD outcomes, including lower systolic and diastolic blood pressure, improved insulin sensitivity, and reduced body fat.3
Although weight loss is a great tool to prevent the development of cardiometabolic disease, adhering to TRE in the long term, to obtain clinically significant results, can be extremely difficult.
Refining eating habits is critical in reducing CVD risk.3 Eating during windows when the body is not equipped for digestion of food, such as at night, impairs metabolism and increases the likelihood of CVD.3 In a recent systematic review consisting of 11 studies, fasting glucose values were significantly lower for participants following a TRE pattern compared to a nonrestrictive-eating pattern.3 People can easily implement TRE as a dietary approach because it does not require changes to the type of food consumed, and a basic level of nutritional understanding is sufficient for using this weight management tool in one’s daily lifestyle.3
When discussing weight management with patients, practitioners need effective tools for evaluating and communicating about standard-of-care approaches that use safe weight-loss interventions. It is crucial to evaluate patients at risk of obesity-related health issues by isolating contributing factors and supportive laboratory findings. Weight reduction of at least 5% to 10% has been associated with improved quality of life, reduction in pain, and lowered CVD risk factors.5 Making necessary dietary changes can have optimal effects on health even without weight loss, resulting in delayed disease progression.6
Weight loss has been found to be 2 times more effective through lifestyle intervention than antidiabetic medication in delaying progression to overt diabetes. Exercise and energy restriction are 2 important factors in improving cardiometabolic health, but the success of other modified lifestyle interventions depends upon individuals and their willingness to comply with dietary changes. Although weight loss is a great tool to prevent the development of cardiometabolic disease, adhering to TRE in the long term to obtain clinically significant results can be extremely difficult.9
TRE may be an effective dietary intervention for weight loss and lowering CVD, but it has several limitations.10 Some individuals may not have access to high-quality food options, the restrictive eating time may not be feasible, and other extenuating circumstances may interfere with compliance. Although there is a need for improved strategies for effective weight management, future studies of TRE should consider other factors that may impact long-term compliance, and longer trial durations are necessary to determine the impact on health over time. However, based on this study, TRE may be considered a beneficial dietary intervention for weight loss and treatment of cardiometabolic disease by improving overall health.