Time-restricted eating may be similar in effectiveness to calorie counting, according to a small study on adults with obesity.
The study looked at 77 adults, primarily Black and Hispanic, and found that the two methods produced statistically similar weight loss over 12 months.
Still, some dietitians say that the consequences of fasting on the body’s hunger cues outweigh the benefits.
A new study on dieting found that time-restricted eating diets without calorie counting are comparable to calorie restriction diets when it comes to losing weight. The results suggest that time-restricted eating may be a useful tactic for people looking to lose weight who cannot financially afford specialized diet plans or who struggle with calorie counting. However, other studies say that time-restricted eating is not linked to weight loss.
Time-restricted eating involves limiting meals and eating periods to a certain window of time each day, usually within several hours, and focusing on sticking to this timeframe rather than maintaining a certain number of calories. Time-restricted eating is considered a type of Intermittent fasting (IF), which also involves restricting the window during which a person eats. Some forms of IF also require calorie restriction or fasting for days instead of hours.
The non-blind clinical trial was published in Annals of Internal Medicine this July, and followed 90 adult participants with obesity for 12 months (from January 2021 to September 2022). The average age of participants was 40; about one-third were Black and 46% were Hispanic.
Researchers separated participants into three groups. The time-restricted eating group followed an intermittent fasting diet, in which participants were confined to eating periods between noon and 8 p.m. but did not count calories. The calorie restriction group followed a diet with a 25% calorie reduction, under which they did count calories. The control group could eat over a period of 10 or more hours per day without the restriction.
The results showed that members of the time-restricted eating group and the calorie restriction group lost more weight than the control group but that one diet was not superior to the other. Members of the dieting groups both lost about 5% of their starting weight over the study period.
Based on these results, the researchers called time-restricted eating an “undoubtedly…attractive approach to weight loss in that it does not require the purchase of expensive food products, allows persons to continue consuming familiar foods, and omits complicated calorie tracking.”
However, some dietitians oppose IF and time-restricted eating as weight loss tactics, saying that the methods discourage people from following natural hunger cues.
In particular, IF can promote cycles of binge eating, starvation, and/or obsessive thoughts, making it a “catalyst for eating disorders,” says Alissa Rumsey, MS, RD, a New York City–based dietitian and author of Unapologetic Eating.
“When you are only allowing yourself to eat during a certain window of time, you end up having to disregard your internal hunger cues,” says Rumsey. “Disregarding hunger cues not only disconnects you from your body signals but also once you are ‘allowed’ to eat, it often ends up that you are starving and it can be hard to stop eating.”
She adds that this can lead to “chaotic and dysregulated eating” or unhealthy food fixations. Multiple studies have linked fasting diets to increased risks for binge eating disorder, bulimia nervosa, and other eating disorders.
“Our body has a strong survival instinct, and when you restrict what or when you're eating, biological mechanisms kick in to make you eat more,” Rumsey says of the mechanisms behind the fasting and eating disorder connection. “Cravings increase, hunger increases, and it becomes really hard to stop eating once you start.”
People with a history of or who are at risk of developing an eating disorder should not attempt an intermittent fasting diet, according to the Center for Discovery, an eating disorder treatment organization that specializes in treating teens and adolescents. People who are not underweight and do not deem themselves at risk of developing an eating disorder can still be vulnerable to “unwanted side effects” from fasting, according to the Center for Discovery. Furthermore, while dieting can promote weight loss, this can include both fat and muscle loss, which can be dangerous.
What this means for you
Time-restricted eating may be similarly effective to calorie counting, according to a small study on adults with obesity. Still, some dietitians say that the consequences of fasting on the body’s hunger cues outweigh the benefits.