How does soy promote weight loss? Scientist finds another clue

May 01, 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: Stem cells faulty in Duchenne muscular dystrophy

add to favorites email to friend print save as pdf

Related Stories

Fingers pointed as climate talks deadlock

8 hours ago

Accusations flew at deadlocked UN climate talks in Lima on Saturday, as the United States warned that failure to compromise could doom the 22-year-old global forum.

Fun cryptography app pleases students and teachers

18 hours ago

Up on Google Play this week is Cryptoy...something that you might want to check out if you or someone you know wishes entry into the world of cryptography via an educational and fun app. You learn more about ciphers and keys; you ...

Recommended for you

Stem cells faulty in Duchenne muscular dystrophy

14 hours ago

Like human patients, mice with a form of Duchenne muscular dystrophy undergo progressive muscle degeneration and accumulate connective tissue as they age. Now, researchers at the Stanford University School of Medicine have ...

Here's how the prion protein protects us

18 hours ago

The cellular prion protein (PrPC) has the ability to protect the brain's neurons. Although scientists have known about this protective physiological function for some time, they were lacking detailed knowledge ...

Regulation of maternal miRNAs in early embryos revealed

19 hours ago

The Center for RNA Research at the Institute for Basic Science (IBS) has succeeded in revealing, for the first time, the mechanism of how miRNAs, which control gene expression, are regulated in the early embryonic stage.

User comments : 0

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.