Intermittent fasting: 8-hour eating window best for weight loss

September 19, 2026 5 min read

There are many diet plans and lifestyle changes people may consider when trying to improve their health. One dietary approach that is becoming more popular is intermittent fasting, which is going without food for a period of time.

One type of fasting is time-restricted eating (TRE). With TRE, people consume their calories during a time window and do not take in any calories outside of that.

Researchers in a new study compared different time-restricted eating window durations and examined their associations with weight loss and markers of cardiometabolic health.

The study is published in the journal Nutrition & Diabetes.

With TRE, the time window people consume food varies by person. Some people use windows of 8, 10, or 12 hours to eat, and then fast for the rest of the day.

TRE typically does not require calorie counting or restricting specific foods, which may make it an easier weight-loss approach for some people. It may not be appropriate for everyone, though, so people should consult with their healthcare providers first.

Prior research shows that TRE can help some people lose weight, but the researchers wanted to determine whether eating-window duration influenced weight loss. They pooled data from five prior TRE studies to take a closer look.

The participants ate over a period of at least 14 hours per day before the trials began.

Of the 124 participants included in the analysis, 95 were assigned to TRE, and 29 served as controls. Eleven participants were assigned to an 8-hour eating window, 59 to a 10-hour window, and 25 to a 12-hour window.

The participants in the control groups either continued their usual eating habits or received brief nutritional counseling and written healthy-eating guidance.

The trials lasted 3 to 6 months, and the participants used a mobile app to track their food and drink intake. They submitted timestamped pictures of their meals and snacks on the app and also added a text description of what they had.

The researchers measured weight, blood pressure, fasting glucose, triglycerides, and HDL cholesterol. They calculated LDL cholesterol in four of the five trials.

Overall, participants in the TRE groups shortened their daily eating windows by about 4 hours and lost an average of 4.8 pounds during the study period.

Participants in the 8-hour group lost approximately 3.7 pounds more on average than those in the 12-hour group. They also lost significantly more weight than participants in the control group.

In the unadjusted analysis, however, researchers did not find a statistically significant difference between the 8- and 10-hour groups. The control group experienced some average weight loss, but the change was not statistically significant.

When the researchers examined the eating windows participants actually achieved, they found that shorter windows were associated with greater weight loss. However, this association weakened after they adjusted for age, sex, and BMI.

When looking at cardiometabolic outcomes, the researchers could not establish a consistent association between eating-window duration and improvements in most measures, including fasting glucose, HDL or LDL cholesterol, and triglycerides.

Participants in the 10-hour group had a greater reduction in systolic blood pressure than those in the 12-hour group, but this was the only significant cardiometabolic difference they found.

The analysis had several limitations, though, including lack of data on participants’ calorie intake, the small number of participants, and the relatively short follow-up period.

Additionally, the five trials the researchers analyzed were not all randomized controlled trials, and participants were not randomized directly into the different eating-window groups.

Cheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center, spoke with Medical News Todayabout the study.

Chen, who was not involved in this research, said that the small sample size, differences among the trials, and short follow-up periods may explain the limited cardiometabolic findings.

“We are still in the early stages of understanding the potential health effects of time-restricted eating,” Chen said.

He added that larger, longer studies are needed to determine who may benefit and whether TRE improves health beyond weight loss.

Chen advised people with type 1 diabetes, hypoglycemia, a history of eating disorders, as well as those who are pregnant or trying to conceive, to consult a healthcare professional before trying TRE.

Mir Ali, MD, a bariatric surgeon, bariatric medicine specialist, and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center, likewise not involved in the study, also shared his thoughts about its findings with MNT.

He noted that the 8-hour group lost more weight than the 12-hour group but said that the modest difference and small sample size mean the results are “not entirely conclusive.”

“Time-restricted eating can be beneficial, but there is considerable individual variability regarding its effectiveness and the optimal fasting duration,” Ali pointed out.

He added that a larger group experiencing more substantial weight loss may be needed to detect consistent cardiometabolic improvements.

Ali warned that conditions such as diabetes may make TRE “less feasible or even contraindicated.” He advised people to discuss their individual health factors with a healthcare professional first.