Johns Hopkins Study Examines Time-Restricted Eating’s Impact on Weight Loss in Adults with Obesity and Prediabetes

A recent study from Johns Hopkins Medicine indicates that time-restricted eating (TRE) can lead to modest weight loss among adults with obesity and prediabetes, without necessitating caloric restrictions.

A study conducted by researchers at Johns Hopkins Medicine has revealed that time-restricted eating (TRE)—a dietary approach that limits food intake to an 8- to 10-hour window each day—can provide modest weight loss benefits for adults suffering from obesity and prediabetes, as well as those with diet-controlled type 2 diabetes. Published on July 27 in the journal Obesity, the research has garnered support from the National Institutes of Health and the American Heart Association.

Understanding Time-Restricted Eating

The study, led by Dr. Daisy Duan, an assistant professor of medicine at Johns Hopkins, seeks to expand the understanding of time-restricted eating beyond the conventional focus on caloric restriction. Previous research primarily examined the impacts of TRE in conjunction with calorie reduction. In contrast, Duan’s study aimed to evaluate whether merely restricting the timing of meals, while maintaining a consistent caloric intake, could induce health benefits related to obesity, such as changes in eating behavior, inflammation levels, and hormone regulation.

The Obesity and Prediabetes Crisis

In the United States, over 100 million adults are classified as obese, while approximately 115 million adults have prediabetes, placing them at heightened risk for cardiometabolic disorders, including hypertension, heart attacks, and strokes. These figures are projected to escalate, underscoring the urgency of effective dietary interventions. Intermittent fasting, a broader term encompassing various fasting and eating patterns, has been linked to weight loss and potential health benefits for individuals facing these conditions.

Study Design and Methodology

In a 12-week randomized controlled trial, the research involved a predominantly female cohort (92%) and Black participants (92%) aged between 18 and 69 years, all of whom had obesity and either prediabetes or diet-controlled type 2 diabetes. Participants were assigned to either a 10-hour TRE schedule or a 16-hour usual eating pattern (UEP) schedule. The TRE group consisted of 19 adults, while the UEP group comprised 20 adults.

All participants adhered to a modified version of the Dietary Approaches to Stop Hypertension (DASH) diet, which emphasizes the reduction of red meat, high-fat foods, sugar, and salt. Each participant’s caloric intake was personalized to maintain their initial weight throughout the study. Meals were prepared and provided by the Johns Hopkins ProHealth Clinical Research Unit in Baltimore, Maryland, under the supervision of trained research dieticians.

Results and Findings

At the conclusion of the study, both TRE and UEP participants exhibited similar modest weight loss, with the TRE group showing a median weight reduction of 2.7% and the UEP group recording a median loss of 2.5%. Moreover, both groups reported improvements in their eating behaviors, including heightened restraint around food consumption, a decreased tendency to eat in response to stress, and a lower overall susceptibility to hunger.

Despite these behavioral changes, the study found no significant differences in appetite hormones—specifically ghrelin and leptin—or inflammation markers, including C-reactive protein, cortisol, and sRAGE, between the two groups. Dr. Duan stated, “We saw that people who followed a 10-hour time-restricted eating schedule lost weight and positively changed their eating habits without calorie restriction. But we did not identify any unique, body-wide health benefits linked to the dietary strategy beyond that.”

Future Research Directions

The research team plans to further investigate how time-restricted eating may assist in weight loss maintenance for individuals who have previously lost weight through other interventions, such as GLP-1 receptor agonists, which are medications used to manage type 2 diabetes.

Conflicts of Interest

The study was authored by researchers including Dr. Daisy Duan, Susan Carnell, Scott J. Pilla, Stephanie T. Chung, Jeanne M. Clark, and Nisa M. Maruthur. Disclosures regarding potential conflicts of interest include Dr. Duan’s consultancy for Rhythm Pharmaceuticals and honoraria from the American Diabetes Association. Dr. Carnell has received grant funding from Eli Lilly and Company, while Dr. Clark serves on a Data Safety Monitoring Board for the same company and holds an advisory role at Novo Nordisk. Dr. Maruthur has received royalties from UpToDate. The remaining authors reported no conflicts of interest.

The study received funding from multiple grants from the National Institutes of Health (R03DK144349, R01DK126825, R01DK139324, K23DK133690) and the American Heart Association (17SFRN33590069).

Broader Implications of the Study

The findings of this study contribute to a growing body of literature suggesting that dietary patterns, particularly those involving time restrictions, may play a critical role in managing obesity and related conditions. While the results indicate that TRE can lead to modest weight loss without calorie restriction, the lack of significant differences in biological markers suggests that further research is essential to understand the underlying mechanisms at play.

Moreover, the study highlights an important trend in dietary research that focuses on the timing of food intake rather than solely on caloric reduction. This approach may provide new avenues for addressing obesity and metabolic diseases that have proven difficult to manage through traditional dietary interventions.

As obesity rates continue to rise, understanding the efficacy and mechanisms of dietary strategies like TRE will be vital for developing comprehensive public health strategies aimed at mitigating the obesity epidemic.