Intermittent Fasting Protects Against Obesity in Study on Mice

There may be something to this trendy new diet.


We’ve all got that one friend who won’t shut up about their diet. One day it’ll be Atkins, another day it’s ketogenic. These days, intermittent fasting is all the rage, but there might actually be merit to it. While Atkins and keto diets are associated with health risks over time, a new study on intermittent fasting shows how it might be helpful for at least some subsets of people.

In a paper published Thursday in the journal Cell Metabolism, a team of researchers at The Salk Institute for Biological Studies in California and the University of California, San Diego, demonstrate that time-restricted feeding — a type of intermittent fasting — can help protect against metabolic disease in mice with abnormal circadian rhythms.

The circadian “internal clock” is important in regulating many physiological processes, including eating schedules, and “clock-deficient” mice have long been known to get fatty livers, high cholesterol, and diabetes — not unlike human shift workers, whose less regulated eating habits tend to result in larger waistlines and worse health. The team’s results suggest that intermittent fasting can minimize those negative health effects, at least in mice.

“We found that [time-restricted feeding] for up to 12 weeks is sufficient to sustain metabolic health in relatively young clock-deficient mice, suggesting that imposed feeding-fasting rhythms and associated metabolic oscillations can override otherwise compromised rhythms,” they write.

Mice without circadian clocks often acquire metabolic diseases and become obese. But time-restricted feeding seems to protect against these health issues.

Alexas Fotos, Pixabay

The genetically “clock-deficient” mice had no natural sleep-wake cycles and thus no way to control their feeding schedule. When given open access to food, these mice are well known to become obese and develop several metabolic diseases, including fatty livers, high cholesterol, and diabetes or pre-diabetic symptoms. Wondering whether they could prevent this, the researchers put the mice on a strict feeding schedule that gave them access to food only 10 hours a day, keeping their total caloric intake the same. Under these conditions, the mice didn’t develop those health issues, which suggested that adjusting the feeding schedule of an animal with compromised metabolism could help override its biology.

Though “intermittent fasting” can refer to a broad range of diets, the researchers prefer not to use the term because it implies caloric restriction.

“The IF research evolved from caloric restriction and implies one has to objectively reduce calories,” Satchin Panda, Ph.D. a professor of regulatory biology at the Salk Institute and the corresponding author on the paper, tells Inverse, but in this study, the mice consumed the same amount of calories whether they were on a time-restricted feeding schedule or not. Be that as it may, the terms “intermittent fasting” and “time-restricted eating” are often used interchangeably in public conversation.

The authors acknowledge a similarity between the mice and shift workers, for whom maintaining healthy eating patterns is not easy because of the limitations imposed by their work. Indeed, there’s even a name for the circadian rhythm disruptions experienced by shift workers: shift worker sleep disorder, which is associated with increased risk of depression, accidents, ulcers, and other health and behavioral issues. Additionally, a 2005 study of US workers found that shift workers sleep almost an hour less per night than day workers. And a 1997 study of Japanese workers found that shift workers have worse heart health, higher cholesterol, and bigger waistlines than day workers.

For shift workers, maintaining healthy habits can be nearly impossible.

Unsplash / Fancycrave

So even though the mice in this study were genetically modified to lack circadian rhythms, the health problems scientists observe in them are actually not so different from those that many workers around the world face when their circadian rhythms are disrupted by their work.

It’s not just work that can mess up our biological clock, though. As we get older, our circadian rhythm can start to change, making sleep disorders more likely. That being said, despite the apparent implications of this study for human health, the study’s authors caution against drawing too many conclusions about humans.

“Although it is easy to impose a strict [time-restricted feeding] on animals, it is premature to conclude that humans with circadian rhythm defects who may be predisposed to aberrant eating pattern can voluntarily impose a strict time-restricted eating protocol to prevent or reverse metabolic diseases,” the researchers write. In other words, we’re not lab animals, so it’s a lot harder to implement this kind of restricted feeding plan. But for people who are at risk of those diseases, it’s probably not a bad idea to consider the benefits of a stricter eating schedule.

Editor’s note: As of 2:45 P.M. Eastern, this article has been updated to include comment from Dr. Satchin Panda.

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