Here’s What This Controversial New Time-Restricted Diet Study Really Shows

The results of a new weight loss study were released this week, making headlines proclaiming that intermittent fasting “isn’t some magic diet trick after all.”

The researchers aimed to test whether adding a restriction on the time of day you were allowed to eat (or not) to the usual low-calorie (or kilojoule) diet led to greater weight loss compared to the simple following a low-calorie diet.

They recruited 139 adults whose average weight was 88 kilograms (194 pounds) and aged 32 years.

Participants were randomized to follow either the low-calorie diet that had reduced their usual daily energy intake by 25%, or the same low-calorie diet with the addition of a period of time during which they were allowed to eat within an eight-hour window. hours between 8 a.m. and 4 p.m. daily.

This approach is called “time-restricted eating” or “16-hour intermittent fasting.” Both groups received support from health coaches to follow their diets for 12 months.

The results showed that after one year, people in both groups had lost 7-10% of their initial body weight. While the low-calorie group lost an average of 6.3 kilograms, the low-calorie, time-restricted group lost 8 kilograms.

Although there was a difference of 1.8 kilograms between the groups, it was not a statistically significant difference.

Participants in both groups also had better blood sugar and blood fat levels and better insulin sensitivity, but again there were no significant differences between the groups.

There are four reasons why this weight loss trial is important.

1. He was not based in the United States

Most studies on intermittent fasting have been conducted in the United States. This trial was carried out in China and recruited people in Guangzhou, so it provides important data using culturally sensitive prescribed calorie restriction over 12 months.

2. He showed that small extra time restrictions for eating don’t make much difference

In their normal life, the participants in Guangzhou had a usual daily eating window of around 10.5 hours. Studies in other populations, particularly in the United States, show that approximately 90% of adults have a 12-hour eating window, with only 10% of adults having an overnight fasting period longer than 12 hours.

For more than 50% of people in countries like the United States, overnight fasting lasts less than nine hours, meaning they eat for a 15-hour period each day.

So in the current study, the time restriction on eating was only minor – about two hours less per day than is usual for people in China. It wouldn’t have been too much of a difference from usual.

The researchers also reported that in China, the largest meal is usually eaten in the middle of the day, so this was not influenced by the time restriction. In countries where the evening meal is the heaviest or where people snack all evening, time restriction can still be a beneficial way to reduce intake.

A 2020 review of 19 studies that used time-limited intermittent fasting found it to be an effective treatment for obese adults, leading to greater loss of body weight and body fat, along with lower blood pressure. significantly lower systolic and blood sugar levels.

3. He showed that support is imperative

Both groups in this trial received a lot of support for adhering to the kilojoule-restricted diet. They received one meal replacement shake daily for the first six months, to facilitate compliance with the kilojoule restriction and to help improve adherence to the diet.

They also received dietary advice from qualified health coaches during the 12 months of the trial. They received dietary information booklets with advice on portion sizes and sample menus.

They were encouraged to weigh food to improve their accuracy in reporting intake in kilojoules and were required to keep a daily diary with photographs of the food eaten and the time, using the study app.

They also received follow-up calls or application messages twice a week and met with the health coach individually every two weeks for the first six months.

For the past six months, they continued to complete their dietary records three days a week and received weekly follow-up phone calls and app messages and met with a health coach monthly. They also attended monthly health education sessions.

It was a lot of support and it’s very important. Receiving long-term support for health behavior changes typically results in weight loss of 3-5% of body weight, which significantly reduces the risk of weight-related health problems, including a reduction in 50% risk of type 2 diabetes over eight years.

4. Even with good compliance, individual weight loss varies

Individual weight loss responses were highly variable, although compliance was high in this trial.

About 84% of participants met the prescribed daily calorie goals and time-restricted eating period. Weight loss at 12 months ranged from 7.8 to 4.7 kilograms in the low calorie only group, and from 9.6 to 6.4 kilograms in the low calorie plus restricted diet group in the weather.

As we have seen many times before, this study confirms that there is no best diet for weight loss. It also shows that small decreases in the time window you eat probably won’t make a difference to weight loss.

Clare Collins, Laureate Professor of Nutrition and Dietetics, University of Newcastle.

This article is republished from The Conversation under a Creative Commons license. Read the original article.