How does soy promote weight loss? Scientist finds another clue

May 1, 2007

Research shows that when soy consumption goes up, weight goes down. A new University of Illinois study may help scientists understand exactly how that weight loss happens.

"We wanted to compare the effects of soy protein hydrolysates and soy peptides with those of leptin because we hypothesized that soy might behave in the body in a similar way. Leptin is a hormone produced in our adipose tissue that interacts with receptors in the brain and signals us that we’re full so we stop eating," said Elvira de Mejia, a U of I assistant professor of food science and human nutrition.

The researchers wanted to see if soy protein hydrolysates could affect these regulatory hormones and their receptors.

"And we found that soy did have an effect on these mechanisms and hormones that are induced in the body to help us degrade lipids and reduce body weight, but it did so by boosting metabolism and not by reducing food intake," she said.

To compare soy peptides with leptin, de Mejia’s graduate student Nerissa Vaughn, with the help of associate professor Lee Beverly, implanted cannulas in the brains of lab rats; they then injected leptin as a positive control. When the scientists could see their model was working, they injected two formulations of hydrolyzed soy protein and soy peptides so the scientists could monitor the effects of each on food intake and weight loss.

Injections were given three times a week for two weeks; during that time, the animals had unlimited access to food and water. Food intake was measured 3, 6, 12, 24, and 48 hours after injection, and the rats were weighed 24 and 48 hours after injection. All rats received the same amount of exercise, and all rats lost weight.

But, after the third injection, de Mejia and Vaughn noticed a significant weight loss in the group of animals that had received one of the soy hydrolysates, even though the animals hadn’t changed their eating habits. In this instance, soy protein appeared to have caused weight loss not by reducing food intake but by altering the rats’ metabolism.

The experiment not only showed that soy peptides could interact with receptors in the brain, it also demonstrated that eating less isn’t always the reason for weight loss, the researcher said.

"Weight loss is a complex physiological event. It’s not always as simple as ‘Eat less or exercise more,’ said de Mejia.

"Losing weight is a cascade of many steps, beginning with the production of certain hormones and continuing with their action in the brain. Some people are resistant to these hormones, just as other people are insulin-resistant. These people never receive the message from the brain that tells them they’re full," she added.

de Mejia plans to continue investigating the effects of soy proteins on weight loss. She believes soy contains anorectic peptides that signal a feeling of satiety as well as peptides that boost the metabolism. Her next step will be to fractionate and purify the soy hydrolysates so that she can identify each peptide and understand its bioactivity.

Source: University of Illinois at Urbana-Champaign

Explore further: Ingesting soy protein may ease severity of inflammatory bowel disease

Related Stories

How do our bones get calcium and why do they need it?

March 30, 2017

Celebrity chef Pete Evans was reported recently as saying "calcium from dairy can remove the calcium from your bones", and can worsen osteoporosis. The Australian Medical Association has expressed concerns that Evans is disseminating ...

Five ingredients that can help with weight management

January 18, 2016

Weight loss is often one of consumers' top resolutions for the New Year. While the basic premise of losing weight is to consume less calories than calories burned, weight management has evolved over the years and includes ...

Recommended for you

Tiny bubbles offer sound solution for drug delivery

June 25, 2017

Your brain is armored. It lives in a box made of bones with a security system of vessels. These vessels protect the brain and central nervous system from harmful chemicals circulating in the blood. Yet this protection system—known ...

Lab grown human colons change study of GI disease

June 22, 2017

Scientists used human pluripotent stem cells to generate human embryonic colons in a laboratory that function much like natural human tissues when transplanted into mice, according to research published June 22 in Cell Stem ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.