- Recent research in the journal Cell Metabolism sought to find out whether or not an intermittent fasting window of four or six hours was better for weight loss.
- There was no noticeable difference between the four-hour and the six-hour windows—if you want to give intermittent fasting a try, choose a timeframe that works best for you.
Over the past few years, intermittent fasting—sometimes called time-restricted eating—has gained attention thanks to studies like this one that suggest it may be helpful for benefits like lowering inflammation and improving insulin resistance (a disruption in how your body processes glucose for energy that can set back your performance and eventually lead to diabetes).
Part of those advantages likely come from potential weight loss, some researchers have noted. This type of fasting limits eating to a certain timeframe, such as a six-hour, or even four-hour window every day. How much of a difference do those two hours make if you’re using the strategy for weight loss?
None at all, a recent study in the journal Cell Metabolism finds. Even though you would be able to eat more within a longer timeframe, it doesn’t automatically mean you would. In fact, you’re actually less likely to overeat overall.
Researchers recruited 58 participants and split them into three groups. One was asked to eat only between 1 p.m. and 5 p.m., while the other could eat from 1 p.m. to 7 p.m. During the “fasted hours,” they were directed to only drink water or calorie-free beverages. The third group acted as a control and made no changes to their diet or eating timeframes.
Apart from asking those in the time-restricted groups to refrain from eating during fasting time blocks, the participants weren’t given any limits or rules on what or how much they could eat.
Participants followed the schedule for 10 weeks and had health markers tracked, including weight, insulin resistance, oxidative stress (a harmful chemical process in your body if there’s too much), blood pressure, LDL (“bad”) and HDL (“good”) cholesterol, triglycerides (a type of fat found in your blood), and inflammatory markers.
There was no change in the control group, but both fasting groups showed reduced calorie intake and averaged a body fat loss of 3 percent.
“The fact that there was no noticeable difference between the four-hour and the six-hour groups is very helpful, because it allows us to recommend that if you’re trying to choose a time window for eating, you should pick one that works best for you,” lead researcher Krista Varady, Ph.D., professor of nutrition at the University of Illinois at Chicago, told Bicycling.
According to Varady, there’s a general belief that if you restrict your eating time, you’ll end up eating more, but she and her colleagues didn’t find that to be true.
“We didn’t ask people to keep calories in mind—they just gravitated toward naturally reducing their intake by about 25 percent. That was surprising,” she said.
Another interesting tidbit from previous research she and her colleagues have done is that alternate-day fasting tends to have a high dropout rate of about 30 percent. But with this study, there were almost no dropouts.
“That tells me this is more sustainable for the average person,” she said. “The takeaway here is that if you want to try this to lose weight, feel free to play around with the timeframe a little, because it will have the same benefits either way.”
