Feeding on stress

Several weeks into a diet experiment, things took a turn.

Researcher David Diamond wanted to see how much weight rats would gain on a typical American high-fat, high-sugar diet compared with rats on a low-carb, Atkins-type diet.

But Diamond, a psychology professor at the University of South Florida, found more than he bargained for: The rats that ate a lot of fat and sugar gained weight , but they also grew anxious.

His fat, stressed-out rats were turning the idea of comfort food on its head.

"Nothing tastes better than a big cheeseburger and fries and an ice cream when you're stressed," Diamond said.

But it might not bring you tranquillity.

Diamond, also an associate professor of molecular pharmacology and physiology, presented his findings this month at the annual Society for Neuroscience conference in Chicago.

It's a continuation of his work for the U.S. Department of Veterans Affairs that has shown stress and a high-fat diet can damage brain cells.

His latest research indicates, however, that the culprit is not fat but the combination of fat and sugar.

Working with graduate student Shyam Seetharaman, Diamond fed one group of rats what he considered a typical American diet: 40 percent fat, 40 percent carbohydrates and 20 percent protein.

They fed another group an Atkins-type diet of 70 percent fat, 20 percent protein and 10 percent complex carbohydrates. Atkins, on its Web site, acknowledges its high-protein "bacon, egg and cheese" reputation but rejects it, saying instead that it is "rooted in eating fewer refined carbohydrates and refined sugars," or bad carbs.

The USF team also used a control group of rats on rat chow, which is low in fat and protein and high in complex carbohydrates, which have a lot of fiber and don't turn directly into sugar in the body as simple carbohydrates do.

About two weeks into the diet, the researchers began to expose the rats to stress. One by one, the rats were put into a box and given a mild electric shock.

A few weeks later the researchers returned the rats to the same box. The high-fat-and-sugar eaters froze in panic. The ones on chow or the low-carbohydrate diet showed no fear.

"They were very curious. They were hyper-curious," Diamond said. "They were looking all over the place. They had much less fear than the other groups."

Diamond doesn't have a firm explanation for why the different diets cause different responses to stress. That's a topic for later research, he said.

But he sees implications for people trying to lose weight. Just as the high-carb-eating rat feels safe in the enclosed space, people feel safe at home on their couches, he said.

"But when they're challenged, that's when there's anxiety," which may cause them to retreat to their couches.

The problem is not the fat they eat, he said. It's the fat mixed with the sugary simple carbohydrates. Cutting way down on the carbohydrates might make it easier for them to get off the couch and face the world.

"The key is the very low carbs," he said. "It's neuroprotective."