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Here’s a reason to eat more whole grains: They may help you lose weight
A new study found that people who eat whole grains instead of white bread and white rice absorbed fewer calories from their food — almost the equivalent of a cookie a day.
It wasn’t much of a change — just swapping out 100 percent whole wheat bread for white bread, brown rice for white rice and whole grain cereal for the more processed stuff.
Just those tweaks added up, however, the team at Tufts University on Boston found. Over six weeks, men and women who ate whole grains took in 92 fewer calories a day than people who ate the precisely same diet with American-style processed grains.
Related: Whole grains help you live longer
That could add up to 5 pounds a year, although the team stresses they did not measure weight loss in the group they studied.
“People who were eating whole grains compared to people who were eating refined grains had a larger excretion of energy in the stools, so they were not absorbing as many of the calories that they were eating,” Phil Karl of Tufts, who did much of the work on the study, told NBC News.
“They were going more, pooping more frequently and in larger volumes,” he added. “Potentially, they were not digesting as much energy from the diet.”
The fiber in the whole grains is not digested, and it can pull out some of the other undigested food with it, Karl said.
For the study, the team recruited 81 men and women aged 40 to 65.
They all got carefully controlled diets. Half got nothing but refined grains, while the other half got nothing but whole grains.
“We provided them all of their food during the eight-week study,” Karl said.
“They came to the lab about three times a week to pick up their food.”
The Tufts staff also tested their blood to make sure the people who were supposed to eat whole grains didn’t cheat, and to make sure those who were not supposed to eat whole grains didn’t sneak in a bowl of oatmeal or some bran flakes.
So, for instance, one group got white bread while the other got whole wheat; one got white rice and the other brown rice and one got regular pasta while the other was fed whole-grain pasta.
Nothing else was different, and the team used commercially available foods. So the rest of the diet was fairly typical, with all of the sugar and fat that Americans usually eat.
After six weeks, the differences were measurable, the team reported in the American Journal of Clinical Nutrition.
“It amounted to about 100 calories per day difference in energy deficit in the whole grain group,” Karl said.
Also, there seemed to be a slight difference in resting metabolism – how many calories a person burns while sitting still, he said. The whole-grain eaters had a slightly faster metabolism.
So would that add up to weight loss? Karl isn’t sure. Human weight loss and weight gain is not an exact science.
But in other studies, eating as little as 100 calories a day more or less adds up to about five pounds a year, he said.
If nothing else, eating whole grains might help people slow the steady weight gain that bedevils most people as they get older, he said.
“We are looking at why whole grains might cause weight loss or prevent weight gain,” Karl said.
“Once you gain weight, it’s very hard to lose.”
How did the team know people were pooping out more calories if they ate whole grains? They checked.
“That was all me,” Karl said. The volunteers collected their bowel movements, which Karl analyzed.
“I was a graduate student at the time,” Karl said. “We get the dirty jobs.”
The study team also checked for gut bacteria – the bacteria that help digest food and that are associated with disease and with obesity. They found the people who ate whole grains had small changes – gaining “good” bacteria called Lachnospira and producing fewer Enterobacteriaceae, which are linked with unhealthy inflammation.