Intermittent fasting vs. calorie counting for weight loss: many of the benefits are similar

“There were no long-term studies that looked at the way people usually do time-restricted eating with an eight-hour window [of restricted eating],” says Krista A. Varady, Ph.D., study author and professor of nutrition at the University of Illinois Chicago. “We wanted to see if weight loss would be better with time-restricted eating versus traditional calorie counting, and it wasn’t.”

The study, which included 90 racially diverse adults with obesity from the Greater Chicago area, randomly assigned participants into one of three groups: 

1. Eight-hour time-restricted eating, wherein participants could eat only between noon to 8 p.m., without calorie counting
2. Calorie restriction, wherein participants reduced 25% of their calories daily
3. No change in their calorie consumption, with meals taking place across 10 hours or more throughout the day. 

Participants in the time-restricted eating and calorie-restriction groups met regularly with a dietitian. Researchers from the University of Illinois Chicago found that participants in the time-restricted eating group ate 425 fewer calories than the control group and lost roughly 10 more pounds than the control group after one year. 

However, participants in the calorie-restricted group ate 405 fewer calories per day and lost about 12 more pounds after one year. Participants in both groups demonstrated strong adherence to their respective interventions.

Researchers believe that access to dietitians likely helped participants in the restricted eating group make healthier food choices and that the study results can help guide clinical decision-making by taking into consideration an individual’s preferences rather than simply choosing a diet that may be deemed more effective. However, further research is needed to determine who would most benefit from each of these interventions.

What is intermittent fasting?

Also called intermittent energy restriction, intermittent fasting is an umbrella term used to describe dietary regimens that involve energy restriction for specific periods of time.

Mark Mattson, Ph.D., author of The Intermittent Fasting Revolution and a professor of neuroscience at Johns Hopkins University School of Medicine, defines it as “eating patterns in which individuals go for extended time periods with little or no energy intake, with intervening periods of normal food intake, on a recurring basis.”

The simplicity of intermittent fasting can appeal to those who find traditional calorie counting to be tedious and time-consuming.

“People can count time instead of counting calories,” says Varady. “The diet is free as well and you don’t have to buy expensive food products, which makes it accessible. For people who got burned out doing calorie restriction, this is a viable option.”

Other health benefits of intermittent fasting

Additional research suggests that intermittent fasting has other health benefits, such as warding off diabetes, heart disease, cancer, and dementia. Intermittent fasting also supports improved insulin sensitivity and reduced inflammation, which can contribute to the aforementioned benefits. Limiting your calorie intake during the first six to eight hours a day can also help stabilize blood glucose levels.

How does intermittent fasting work?

There are multiple methods of intermittent fasting. Time-restricted eating is among the most popular for weight loss and involves consistent fasting and eating periods within a 24-hour cycle in which food intake is restricted to a time window of eight to 10 hours or less per day.

Other options include fasting for an entire 24-hour cycle one to three days per week or drastically reducing your calorie intake on two or more days a week. But intermittent fasting isn’t for everyone.

“If you are pregnant, breastfeeding, on insulin for diabetes, or have a history of eating disorders, we don’t want to go down this road,” Caroline Susie, registered dietitian nutritionist and a spokesperson for the Academy of Nutrition and Dietetics, previously told Fortune.

Additionally, time-restricted eating is not advised for people with a body mass index under 18.5, the elderly, and people with eating disorders. Varady also noted intermittent fasting is not likely to increase the propensity of developing an eating disorder in people without a history of one.

If you’re curious about intermittent fasting but aren’t sure if it’s safe for you, consult with your doctor first.