Eating all your meals and snacks in an eight- to 10-hour window each day may help you to lose weight and improve your blood sugar control, new research suggests.
The findings, published September 30 in Annals of Internal Medicine, add to a growing school of evidence that intermittent fasting has promising health benefits, particularly for people who want to tackle their metabolic health.
Intermittent fasting is a hugely popular diet, often touted by celebrities, longevity influencers, and C-suite executives. The idea is that it's not just about what you eat, but when. Adherents limit all of their food intake to a specific window of time each day, which varies based on which style of fasting they follow.
In the new study, people who fasted for three months lost more weight than those who didn't, and ate fewer calories without specifically trying to.
Here's more detail:
The study, explained
A research team from the University of California San Diego School of Medicine and The Salk Institute wanted to test whether fasting could help people with metabolic syndrome, a collection of risk factors for chronic illnesses. The condition includes high blood sugar as well as high levels of body fat, and increases the odds that someone will develop heart disease and diabetes.
For three months, the researchers followed 108 adults with metabolic syndrome, in theirs 50s on average.
Half of the participants were randomly assigned to follow their typical eating pattern, with some general nutrition advice about healthy eating, such as seeking inspiration from the Mediterranean diet.
The other half were given the same advice, but were also instructed to limit their eating to eight to 10 hours a day, and tracked their eating on a smartphone app called myCircadianClock.
By the end of the study, both groups lost a small amount of weight. However, participants who did intermittent fasting lost a bit more weight, and had a much bigger drop in their body fat percentage, since more of the weight they lost was fat instead of muscle.
They also had significantly better blood sugar control and HbA1c, a measure of average blood sugar over time that's used to screen for diabetes and prediabetes.
Fasting works by helping you eat less, experts say
The science behind fasting suggests it's effective because it helps you eat less.
The fasting group in the newest study ate 350 fewer calories on average each day, according to the data, although they weren't specifically asked to cut calories. Most of that calorie reduction came from eating fewer carbohydrates and less fat. They ate about the same amount of protein.
Previous evidence suggests that eating enough protein can help maintain muscle during weight loss. That may explain why participants in this study held on to their muscle mass, while other research has found some kinds of fasting may have a risk of muscle loss.
To get the benefits of fasting, stop eating at night
Another potential benefit to fasting is that it helps you tap into your body's natural internal clock, known as circadian rhythm, Satchidananda Panda, a pioneer in fasting research and co-author of the latest study, previously told Business Insider.
Panda and other experts say the easiest way to start reap the benefits of fasting is to stop eating three hours before bed.
This simple 12-hour fast may boost your health and help cut down on potential junk food snacking, too.
