Time-restricted eating has become a popular way to approach weight loss without focusing on calorie counting. The idea is simple: eat during a set number of hours each day, then fast the rest of the time.
But a new study published in Obesity suggests the shorter eating window itself may not provide extra benefits when people are eating similar foods and similar amounts.
In the 12-week randomized controlled feeding study, adults with obesity and prediabetes or diet-controlled type 2 diabetes were assigned to eat within either a 10-hour window or a 16-hour window. Both groups lost a modest amount of weight, but the difference between them was minimal. The groups also showed similar changes in hunger, eating behavior and several measures tied to appetite and inflammation.
That makes the study a useful reality check on a common assumption about intermittent fasting: that simply eating within a shorter window may have special effects beyond the food itself.
Researchers analyzed 39 adults who completed the study. Their average age was about 60, and most participants were women and Black. Everyone had obesity along with prediabetes or type 2 diabetes managed without medication.
The researchers also controlled what participants ate. Both groups received the same study-prepared diet, with similar amounts of protein, carbohydrates and fat. The main difference was timing.
People in the time-restricted group ate during a 10-hour window that ran from morning into early evening. Those in the comparison group could eat across a 16-hour window that extended later into the day.
By the end of the study, the 10-hour group had lost about 2.7% of their body weight. The 16-hour group lost about 2.5%. Statistically, those results were essentially the same.
That means the study does not show that the shorter eating window led to greater weight loss.
Both groups also reported some changes in how they approached food. Participants generally showed more control around eating and less tendency to eat in response to hunger or other cues. But again, the 10-hour eating window did not stand out from the longer one.
The researchers noted that simply being part of a highly structured feeding study may have helped. Everyone received planned meals, followed a set schedule and may have been eating more deliberately than they did before the study began.
The team also looked for signs that time-restricted eating changed the body’s response to hunger or inflammation. They did not find meaningful differences between the two groups.
“We saw that people who followed a 10-hour time-restricted eating schedule lost weight and positively changed their eating habits without calorie restriction,” study author Daisy Duan of Johns Hopkins University School of Medicine said in the university release. “But we did not identify any unique, body-wide health benefits linked to the dietary strategy beyond that.”
That does not mean time-restricted eating is useless. A shorter eating window may still be a practical structure for people who find it easier to follow than other approaches.
What this study suggests is that the timing alone may not be doing as much as people sometimes assume, at least under these conditions.
There are important limits to the findings. The study was small, with only 39 participants, so it may not have been able to pick up more subtle differences. The researchers also cautioned that finding no significant difference does not prove the two eating patterns are identical.
The study population was also fairly specific, with most participants being older Black women, so the results may not apply the same way to younger adults, men or other groups. This analysis was also conducted after the original trial, rather than being designed from the start specifically around hunger and inflammation.
The research was supported by the National Institutes of Health and the American Heart Association. Several authors reported financial relationships with pharmaceutical companies, including Eli Lilly, Novo Nordisk and Rhythm Pharmaceuticals.