There’s a lot of enthusiasm for intermittent fasting — a term that can encompass everything from skipping a meal each day to fasting a few days a week.
Or, how about this approach: Simply limit your daily eating window to 10 hours. This means that if you take your first bite of food at 8 a.m., you’d need to consume your last calorie of the day by 6 p.m.
A new study published in Cell Metabolism offers some evidence that the approach can be beneficial.
Researchers tracked a group of overweight participants who followed this approach for about three months. “Typically, people would go for an 8 a.m. to 6 p.m. eating window,” explains Dr. Pam Taub, a cardiologist at the University of California, San Diego’s School of Medicine, and an author of the study.
During the fasting period, participants were encouraged to stay hydrated with water. Each day, they logged the timing of their meals and their sleep in an app.
“We saw a 3% reduction in their weight and a 4% reduction in abdominal visceral fat,” says Taub.
“We didn’t ask them to change what they eat,” she explains, though participants consumed about 8.6% fewer calories — likely as a result of the limited eating window.
In addition to the weight loss, “we saw that cholesterol levels improved and blood pressure [levels] also improved,” Taub explains. There was also some reported improvement in sleep quality, and many of the participants reported more energy.
“We are surprised that this small change in eating time would give them such a huge benefit,” says Satchidananda Panda, a professor at the Salk Institute for Biological Studies and a co-author of the study. Panda and Taub have some theories that may help explain the reduction in belly fat and weight loss.
“When you go into a fasting state, you start to deplete the glucose stores in your body and you start to use fat as your energy source,” Taub explains. “You can enter a low-grade state of ketosis.”
And once stored fat is fueling your body, “that can lead to a good amount of weight loss,” Panda says.
There are still lots of unanswered questions when it comes to fasting, such as: Are shorter windows of fasting effective? “There is recent data to show that time-restricting [eating to] even 12 hours has beneficial effects,” says Dr. Phyllis Zee, the director of the Center for Circadian and Sleep Medicine at Northwestern University’s Feinberg School of Medicine. She was not involved in the new study, but we asked her to take a look at it. “What is interesting is the result on weight loss within 12 weeks,” Zee says.
The study was small, just 19 people. All the participants were overweight and had a cluster of risk factors (elevated blood sugar, elevated cholesterol levels and high blood pressure) that put them at higher risk for Type 2 diabetes and heart disease. A larger study, funded by the National Institutes of Health, is underway to examine daily fasting in people with metabolic syndrome.
For now, the new findings offer some preliminary evidence of the benefits of daily fasting. Taub says you can think of a few extra hours of daily fasting as a way to give your metabolic organs a rest.
“When you’re constantly giving the body calories, you’re constantly making your cells work,” she says. Just as your body and brain feel refreshed after a good night’s sleep, the researchers say fasting can help restore and rejuvenate your organs.
This is not the first research to show that the timing of meals can make a difference to our waistlines. As we’ve reported, a study several years back found that dieters who ate their main meal of the day before 3 p.m. lost about 5 pounds more than people who ate a dinner meal late in the evening.
And as scientists learn more, it’s clear that our bodies are timekeeping machines. Not only do we have a master clock in our brains, but there are also clocks in all the organs of our body — from the pancreas to the stomach and liver.
Daylight is a main cue to reset our master clock each day, but it’s the first bite of food we take in the morning that may be an important cue to reset other clocks in our organs.
“When the timing of meals does not match with the sleep-wake cycle well, there’s a disconnect between the different clocks that we have in basically all the cells of our body,” Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital, told us several years back.
“When the clocks in our body are out of sync,” our bodies don’t work as efficiently, and this may lead us to store more fat, explains Panda. “And over a long period of time, that can lead to Type 2 diabetes, obesity and increased risk for heart diseases,” Panda says.