Does time-restricted eating work?

Is intermittent fasting no better for weight loss than simply reducing calories?  A new study in the prestigious New England Journal of Medicine concludes there’s no significant difference between regular meal times and a more condensed eating window if the number of calories consumed across the day is kept the same.

However, there’s more to intermittent fasting than simply comparing calories, says Diet Doctor Medical Director Dr. Bret Scher. Diet quality, the amount of carbs you eat, whether you are fat adapted, and other factors come into play, such as how easy you find either to do. 

As Dr. Scher notes in this DDNewsvideo, the NEJM study should not be used to dismiss intermittent fasting as useless. Rather, it should help inform individuals to find the approach that works best for them.

 In short, both intermittent fasting and traditional calorie restriction can lead to weight loss, so choose the one that is easiest for you to stick with.

“This is where personalization comes into play,” said Dr. Scher. “Because for some people, it’s really hard to sustainably reduce your calories all day because of hunger. Consolidating it into a smaller eating window is more beneficial and easier for them to do.”

However, Dr. Scher cautioned, if you are the sort of person who tends to overeat after fasting, then restricting calories across the day may work better for you.

“I have found, in my practice, and other clinicians report the same, that some people, when they condense their eating into a smaller window, feel like they have to make up for it. They get the urge to eat more. So maybe time-restricted eating is not right for you.”

The NEJM study took place in Israel and randomly assigned 139 patients with obesity to one of two year-long weight loss programs with the same amount of calories consumed each day. In one arm, the subjects ate their reduce calorie meals during an 8-hour, time-restricted window (between 8 am and 4 pm). In the other arm, the subjects ate the same number of calories without time restriction The women in both groups of the study ate 1200 to 1500 calories a day and the men 1500 to 1800 calories. 

After a year, the mean weight loss in the time-restricted eating group was 8.0 kilos. In the calorie restriction without time restriction group it was 6.3 kilos (which was statistically insignificant.)

 New England Journal of Medicine: Calorie restriction with or without time-restricted eating in weight loss

But Dr. Scher notes the trend lines in the time-restricted groups were slightly better for all markers such as weight loss, BMI, body fat percentage, and waist size.

As well, the study did not compare other components of the diet like food quality or variations in macronutrient percentages, but just considered the number of calories consumed. Both diets were 50% carbohydrate and less than 20% fat.

“It is not just about calories. It matters what you eat,” said Dr. Scher. “So I would love to see a study that looks at time-restricted eating in the context of the quality of the diet. In the context, for example, of a high protein, high fiber, lower carb diet. One that makes you feel more full and satisfied so it is easier to naturally lower your calories and eat less across a day.”

Each week, Dr. Scher creates two or three videos that review relevant or interesting scientific studies in the fields of nutrition, exercise, health, or disease and carefully analyses the researchers’ methods and findings. In doing so, he helps you better understand how to judge the quality of various research papers and make informed decisions about your own health and wellness. 

You can find more of Dr. Scher’s news videos on the Diet Doctor Youtube Channel. Subscribe to the feed so that you don’t miss any of his videos.

Or you can get more information about how to do a low carbohydrate high protein diet, and add in intermittent fasting to see if it is right for you.

Or you can find out more about how to get started on a keto diet here


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