Scientists look at how fiber makes us feel full

Fiber — that might be roughage to your grandmother — has long been considered healthy, and even a factor in weight control, but scientists haven’t figured out how. A study of mice might help shed some light on the mechanism.

The scientists noted that during the Paleolithic period and in some tribes of hunter-gatherers, a person generally ate more than 100 grams of fiber a day; today that figure is 10 to 20 grams in Western diets, they wrote this week in the journal Nature Communications.

The researchers looked at one of the substances produced when fiber is fermented in the gut — acetate, a short-chain fatty acid — and found that when it was consumed, calorie consumption decreased for two hours in the mice.

Epidemiological studies have linked fiber from plant foods to weight, the researchers said. But few people are consuming fermentable carbohydrates at amounts eaten in previous ages, the researchers said, because of unwanted gastrointestinal side effects or unpalatability of the foods.

The scientists, working in Great Britain and Spain, found that the acetate may directly affect the hypothalamus, and that part of the brain in turn is involved in regulating appetite.

William Colmers, an electrophysiologist who studies the effect of neurotransmitters in the hypothalamus at the University of Alberta in Edmonton, Canada, told the journal Nature that the results of the experiment may have been overinterpreted.

“Much of it is extremely speculative,” he told the journal. He said that at the level of fiber used, “the room would be full of mouse farts,” and the animals may have eaten less because they were uncomfortable.