Dr. Shahar Madjar

I have written before about intermittent fasting. I have concluded that intermittent fasting works, but not necessarily better than calorie-restricting diets. Two things have happened since I have last addressed the subject.

First, I have witnessed a dramatic weight-loss in several people who chose intermittent fasting as their weight-loss program (these people include a family doctor I know that has shed more than 30 pounds, and a car-dealer who looks like a much younger and thinner version of his prior self after dieting).

Second, a new study was recently published in the New England Journal of Medicine that shed additional light on intermittent fasting. I decided to revisit the subject and to inform you as to my findings.

The idea behind intermittent fasting is simple: shorten the period of time for eating within each 24-hour period. Typically the types and amounts of food on intermittent fasting aren’t restricted.

Scientists aren’t sure how intermittent fasting works. Some believe that intermittent fasting leads to adaptive physiological responses, improved regulation of glucose and insulin levels, decreased levels of inflammation, and enhanced resistance to stress. Others hold the opinion that the effect is merely one of decreased caloric intake: a shorter time-window for eating, could result in lower calorie consumption.

The new study is a collaboration between scientists in Guangzhou, China; and in Tulane University, New Orleans. The findings were published in April 2022.

The researchers randomized a group of 139 patients with obesity into two groups. Both groups were instructed to restrict their caloric intake (to 1,500-1,800 calories a day in men and 1,200-1,500 calories a day in women). In addition, participants in one of the two groups were instructed to limit their eating to an 8 hour period between 8 a.m. and 4 p.m. In other words, one group was asked to follow a caloric restriction program while the other was advised to adhere to both caloric and time restrictions.

Of the 139 participants, 118 (84.9%) completed a full year of follow-up. At 12 months, both groups had similar results: both groups lost significant amount of weight. The time and caloric restriction group lost 8 kg while the caloric-restriction group lost 6.3 kg. These differences between the groups weren’t statistically different. The two groups had similar results also when other factors were examined (such as waist circumference, BMI, body fat, and body lean mass). There was a decrease in both systolic and diastolic blood pressure in both groups. There were also no differences between the groups in their glucose (sugar) levels, insulin levels, or lipid levels.

In reading the results of any new study, I try to define what questions the study is trying to address and what questions remains unanswered. This study was conducted in China. It compared caloric-restriction with calorie and time- restriction. Participants in the time-restriction group were asked to eat only between 8 a.m. and 4 p.m. because in China (as in many other countries around the globe), as opposed to the USA, the main meal of the day is consumed at lunch time.

So in reading this study, I consider the questions it doesn’t answer. For example, the study compares calorie-restriction with a caloric- and time-restriction, but it doesn’t directly compare caloric-restriction with time-restriction. Also, are the results applicable to different populations (people who live in the USA, for example, or patients with specific medical problems such as diabetes)? Would the results be the same if the fasting period would be 8PM to noon time the following day?

With this limitations in mind, this is a well-conducted study that aims to answer an important question: Does adding time-restriction to a calorie-restriction diet result in a more significant weight loss, or in any other additional health benefit? The answer, at least in the specific population that was studied, appears to be a resounding No!

What does this study mean for you, or for me? Simply put, if you chose a calorie-restricting diet, adding intermittent fasting to the regimen is unlikely to lead to additional health benefits. You should chose a diet you feel comfortable with, and, most importantly, one that you can stick with for a long period of time.

Dr. Shahar Madjar is a member of Aspirus Medical Group based out of Laurium. He specializes in urology.