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Jamshed H, Steger FL, Bryan DR, et al. Effectiveness of early, time-restricted nutrition for weight loss, fat loss, and cardiometabolic health in adults with obesity: a randomized clinical trial.JAMA Intern Med. 2022;182(9):953-962.
Study objective
To examine the effects of time-restricted eating versus consuming food for periods longer than 12 hours to determine which is more effective for fat loss, weight loss, and cardiometabolic health
Key to take away
Dietary intervention with time-restricted eating is more effective for weight loss, improving diastolic blood pressure and mood than eating during a window of more than 12 hours daily.
design
A parallel-arm, randomized, controlled trial lasting 14 weeks
Participant
Obese participants aged 25 to 75 years (mean age 43) were recruited for a weight loss treatment trial at the University of Alabama at Birmingham Hospital (UAB) Weight Loss Medicine Clinic.
A total of 656 people were examined and 90 participants were included in the study; 72 of the participants were female (80%) and 18 were male. Participant ethnicities included 2% Hispanic, 94% non-Hispanic (specifically, Asian 2%, Black 33%, and White 62%), and 3% who reported unknown.
The inclusion criteria were that participants had a body mass index (BMI) between 30 and 60, without a history of diabetes or other unstable diseases or cardiometabolic risk factors assessed.
Interventions
A weight loss treatment in which participants were randomly divided into two groups and assigned to a nutritional plan with a hypocaloric diet for 6 days per week. The groups consisted of: an early time-restricted eating plus energy restriction group (eTRE+ER; based on an 8-hour eating window from 7:00 a.m. to 3:00 p.m.) and a controlled eating schedule plus ER (CON+ER) group (≥12-hour window).
Evaluated study parameters
Participants received weight loss counseling from a nutritionist at weeks 0, 2, 6, and 10. Dual X-ray absorptiometry (DEXA) was used to measure body composition every two weeks. Fat loss was measured by the ratio of fat loss to weight loss and the difference in fat mass. Standard procedures were used to measure fasting blood pressure, homeostatic model beta cell function, insulin resistance, plasma lipid levels, and hemoglobin A1c.
Additionally, researchers assessed adherence to eating windows through surveys. They used food records to measure macronutrient composition and energy intake, followed by post hoc analysis. The study used multiple questionnaires to assess mood, sleep, physical activity and satisfaction with meal times.
Primary results
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 and hemoglobin A1cand plasma lipid levels. Other outcomes measured included satisfaction, adherence, physical activity, sleep and mood.
Key findings
The eTRE+ER group adhered to an eating schedule of 6 days per week (0.8) and the CON+ER group adhered to a schedule of 6.3 days per week (0.8).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 total weight loss 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 on the primary endpoints of weight loss (−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. Additionally, the eTRE+ER group experienced a significant reduction in caloric intake with an additional reduction of 214 kcal/day (95% CI, −416 to −12 kcal/day;P=0.04) relative to CON+ER.
Finally, eTRE+ER was more effective in reducing mood disorders and improving mood in the following subcategories: vigor-activity, fatigue-sluggishness, and depression-dejection. Both groups had similar dietary intake, cardiometabolic risk factors, physical activity, and sleep outcomes.
transparency
The study was approved by the UAB Institutional Review Board 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, the Nutrition Obesity Research Center, and the Diabetes Research Center. One of the study authors, Corby K. Martin, invented the technology for the app used in this study to assess dietary intake, and the center where this study was conducted has an interest in the intellectual property.
Implications and limitations for practice
Cardiovascular disease (CVD) contributes to serious health problems worldwide. It is the leading cause of morbidity and mortality, affecting millions of people each year.1 In the United States, two out of three adults are overweight and one out of three are obese.2 Obesity is associated with excessive body fat, which increases insulin resistance, blood lipids, and systemic inflammation, increasing the risk of developing cardiovascular disease, type 2 diabetes, and insulin resistance.3Diet and other modifiable lifestyle factors have become an important factor in reducing the burden of cardiovascular disease.4Dietary habits and poor eating habits are associated with cardiometabolic risk factors for cardiovascular disease, including high total cholesterol, elevated blood pressure, and elevated BMI.3
Time-restricted eating (TRE) has been found to reduce cardiovascular disease and increase weight loss by allowing people to eat during a restricted schedule, thereby preventing stress on the circadian system from changing eating habits.3TRE 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 an excellent tool for preventing the development of cardiometabolic diseases, it can be extremely difficult to adhere to TRE long-term and achieve clinically significant results.
Improving eating habits is crucial to reducing the risk of cardiovascular disease.3Eating during windows of time when the body is not equipped to digest food, such as at night, impairs metabolism and increases the likelihood of cardiovascular disease.3In a recent systematic review that included 11 studies, fasting glucose levels were significantly lower in participants who followed a TRE pattern compared to participants who followed a non-restrictive diet.3People can easily implement TRE as a nutritional approach because it does not require any changes to the type of food consumed and a basic level of nutritional understanding is enough to use this weight management tool in daily lifestyle.3
When physicians discuss weight management with patients, they need effective tools to assess and communicate about standard treatment approaches that utilize safe weight loss interventions. It is critical to evaluate patients at risk of obesity-related health problems by isolating contributing factors and supporting laboratory findings. Weight loss of at least 5 to 10% has been associated with improved quality of life, reduced pain, and reduced risk factors for cardiovascular disease.5A necessary change in diet can have optimal effects on health even without weight loss and lead to a delayed progression of the disease.6
Weight loss through lifestyle interventions has been found to be twice as effective as through antidiabetic medications in delaying progression to overt diabetes. Exercise and energy restriction are two important factors in improving cardiometabolic health, but the success of other lifestyle change interventions depends on the individual and their willingness to adhere to dietary changes. Although weight loss is an excellent tool for preventing the development of cardiometabolic diseases, long-term adherence to TRE can be extremely difficult to achieve clinically significant results.9
TRE may be an effective dietary intervention for weight loss and cardiovascular disease reduction, but it has several limitations.10Some individuals may not have access to quality food, restricted meal times may not be feasible, and other extenuating circumstances may affect 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 study durations are needed to determine health effects over time. However, based on this study, TRE can be considered a beneficial dietary intervention for weight loss and treatment of cardiovascular disease by improving overall health.