An article from Norwegian SciTech News at NTNU

Fasting 15 hours a day has a major impact on preventing obesity, according to a study done on rats. Clinical studies on adolescents who struggle with obesity are needed to see whether this finding also applies to human beings. (Illustration photo: Colourbox)

Eating only during active hours reduces risk of obesity

A new study of rats suggests that it’s not just what you eat, but when you eat it that affects weight loss or gain.

Gemini, NTNU Trondheim - Norwegian University of Science and Technology

NTNU is the second largest of the eight universities in Norway, and has the main national responsibility for higher education in engineering and technology.

Researchers at NTNU recently published an article about obesity and eating patterns, based on experiments done on rats.

Fifty rats were part of the study and were divided into two groups. One group had access to a high-fat diet throughout the day, while the second group only had access to the same high-fat diet nine hours a day, for five days a week. On the other two days of the week, the restricted group could also eat as much as and whenever they wanted.

For people, this regimen “would mean eating breakfast, lunch and an early dinner, but nothing in the evening,” says PhD candidate Magnus Kringstad Olsen. “Or skip breakfast, and eat lunch, dinner and some evening fare. On weekends you could eat whenever and whatever you want,” he adds.

Eat during active hours

Olsen has been part of a research group for experimental surgery in NTNU’s Department of Cancer Research and Molecular Medicine, under the leadership of Professor Duan Chen.

This time restriction allows you to eat during the hours when your body is active and not at night, when most of us are passive. According to Olsen, what time of day we eat makes a big difference.

“We have an internal clock that is set differently for daytime and nighttime. The body handles food better during the day than at night. Many people who are overweight eat at night,” he says.

Slowed down development of obesity

The results from their study show that fasting for about 15 hours a day has a major influence on preventing obesity.

“We found that rats, particularly young rats that have had high-fat diet but were on the fasting regimen gained weight and developed obesity much more slowly than the rats that ate a high-fat diet whenever they wanted to all week long. The rats that were allowed to eat whenever they wanted gained a lot of weight. People who don’t eat a diet that is as rich in fat as the high-fat diet that the rats ate will probably see an even greater effect,” says Olsen.

The study is in line with a previous experiment in the United States, where researchers looked at the effect of fasting on adult mice that were already overweight.

Tackling overweight among children

In this latest study, NTNU researchers wanted to investigate how a time restriction like this might prevent obesity, especially among children and adolescents.

According to a report from the World Health Organization, 13 per cent of the world’s population are overweight, and that number is on track to double over the next 35 years.

Many people who suffer from obesity are children. The EU Action Plan on Childhood Obesity 2014-2020 outlines measures to prevent overweight among children and adolescents. This has led researchers to seek new dietary guidelines that can prevent obesity without causing malnutrition. Children depend on adequate nourishment to develop normally.

Diet to be tested on youth

The total caloric intake was not reduced in the time-restricted feeding study on rats, which means the diet may be appropriate for young people.

“We’re limited in what we can do for children and adolescents when it comes to obesity. Individuals have to be 18 years old to have an operation, and restricting calories isn’t good for growing children,” says Olsen.

The next step will be to test whether the fasting diet works in practice.

“We would like to start a clinical study on teens under 18 who are already struggling with obesity,” he says.

Whether this kind of diet is effective for weight loss, Olsen can’t yet say. “That remains to be seen,” he says.

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