Flying into obesity: Could jet lag be making you fat?

SCIENTISTS from Israel claim rhythms in our gut become disrupted when we change time zones.

Bad news for regular flyers as scientists link jet lag with weight gain.

IF you put on weight on business trips, don’t blame the hotel meals or the late-night drinking.

Blame, instead, your jet lagged gut bacteria.

Scientists from Israel have discovered a strong circadian rhythm among the organisms that live in our gut, which seems to become disrupted when we change time zones. The research, the result of a study of mice and humans, is doubly interesting: first because it could explain longstanding results that show shift workers are more prone to obesity, and second — arguably more fundamental — because the sun rarely shines into one’s bowels.

“We were very surprised to see that gut microbes have this diurnal variation, both in composition and function,” Eran Elinav, from the Weizmann Institute of Science in Rehovot, said.

“The point here is our gut microbes live completely in the dark, yet feature this very striking circadian behaviour. How do they feel something they are not exposed to?”

Having measured the composition of the microbes in mice and humans who were put into different time zones, the scientists believe that the microbes tell the time by responding to our eating patterns, adjusting their cycle to match meal times.

The results of the research are published in the journal Cell.

Humans contain a whole host of fauna, known as the microbiome, the function of which is only partly understood. It is believed that one role of this ecosystem is in digestion.

When this was artificially disrupted by moving mice in the study to a different time zone, they fed more erratically, put on weight and developed metabolic problems associated with diabetes.

Dr Elinav said that he began the project to see if there were other explanations for so-called modern diseases such as obesity, which have arrived since the Industrial Revolution and the ability to have cheap lighting at night.

“Obesity, glucose intolerance and other metabolic syndromes have reached epidemic proportions in the western world,” he said. “This tremendous rise is associated with a new tendency to disrupt sleep patterns.”

He does not believe that this is the only explanation, but rather could be one of a number of factors that have come together to produce a profound shift in human metabolism.

While the study represents terrible news for airline workers, not least the staff at an Indian airline that sacked stewardesses for being fat, Dr Elinav said that it also offered hope.

“We and others are developing new methods to target the microbiome,” he said. He believes that one day there could be a treatment to counteract the effect. “Our discovery could enable probiotic or antimicrobial interventions in people who have lifestyles they can’t change, to compensate for the time shifts,” Dr Elinav said.

THE TIMES