A Johns Hopkins Medicine study reports evidence that time-restricted eating (TRE) — a form of intermittent fasting that involves only eating during a consistent, daily 8- to 10-hour window — can cause modest weight loss in adults with both obesity and prediabetes or those with diet-controlled type 2 diabetes.
The National Institutes of Health and American Heart Association-supported study, described July 27 in the journal Obesity , represents the latest findings from ongoing research led by Daisy Duan, M.D. , an assistant professor of medicine and the study's primary author, on how time-restricted eating without caloric restriction may change the body's weight and other functions.
Other studies on time-restricted eating, Duan says, examined it with respect to either intentional or unintentional calorie restriction. The new study, she said, focused on whether restricted meal timing while ensuring consistent calorie intake would change other obesity-related factors, such as eating behavior, inflammation, and appetite hormones.
More than 100 million adults with obesity and 115 million adults with prediabetes in the United States are at an increased risk of cardiometabolic complications, such as high blood pressure, heart attack and stroke, and these numbers are expected to rise. Intermittent fasting — an umbrella term for structured patterns of fasting and eating that focus on changing when a person eats instead of reducing calories or avoiding certain foods — has broadly been linked to weight loss and may benefit individuals with either or both conditions.
Broadening clinical understanding of time-based dietary interventions, Duan's team investigated whether health benefits linked to intermittent fasting and other time-based dietary plans are caused by weight loss alone or if other biological mechanisms are also involved.
In the 12-week study, a predominantly female (92%) and Black (92%) cohort of adults (ages 18–69 years) with obesity and prediabetes or diet-controlled type 2 diabetes were randomly assigned to a 10-hour time-restricted eating (TRE) schedule (19 adults) or a 16-hour usual eating pattern (UEP) schedule (20 adults).
All study participants received the same adapted Dietary Approaches to Stop Hypertension (DASH) diet — a heart-healthy diet that emphasizes limiting red meats, high-fat foods, sugar and salt intake — and the caloric intake of each person was personalized to maintain their starting weights.
All meals were prepared and provided by the Johns Hopkins ProHealth Clinical Research Unit in Baltimore, Maryland, under the supervision of research dieticians.
Before and after the study, participants provided fasting blood samples that were used to measure inflammation markers and appetite hormone levels and completed a Three-Factor Eating Questionnaire — a tool that captures how a person interacts with and thinks about food. The researchers used both to track and compare physical and psychological changes over time.
Notably, at the study's conclusion, the researchers observed similar and modest weight loss in both the group that followed the time-restricted eating (median 2.7%) and the usual eating pattern (median 2.5%) meal schedules.
At the end of the study, participants from both groups reported greater restraint around food, a reduced tendency to eat when stressed, and a lower susceptibility to hunger overall after the study's conclusion. However, the appetite hormones (ghrelin and leptin) and the inflammation markers (C reactive protein, cortisol and sRAGE) were comparable between TRE and UEP participants.
"We saw that people who followed a 10-hour time-restricted eating schedule lost weight and positively changed their eating habits without calorie restriction," says Duan. "But we did not identify any unique, body-wide health benefits linked to the dietary strategy beyond that."
Future directions for the research include exploring how time-restricted eating shapes weight loss maintenance in people who have successfully lost weight through other interventions, such as via GLP-1 receptor agonists.
In addition to Daisy Duan, researchers who authored the study are Susan Carnell, Scott J. Pilla, Stephanie T. Chung, Jeanne M. Clark and Nisa M. Maruthur.
The study authors have the following conflict-of-interest disclosures to share: Duan serves as a consultant for Rhythm Pharmaceuticals and receives honoraria from the American Diabetes Association. Carnell receives grant funding from Eli Lilly and Company. Clark participates on a Data Safety Monitoring Board for Eli Lilly and Company and serves on the advisory board of Novo Nordisk. Maruthur receives royalties from UpToDate. The other authors declare no conflicts of interest.
The study was supported by the National Institutes of Health (R03DK144349, R01DK126825, R01DK139324 and K23DK133690) and the American Heart Association (17SFRN33590069).
DOI: 10.1002/oby.70270
