I wonder if eating a lowcarb, high fat diet disrupts the stress response and enables us to lose weight without becoming more hungry. One of the most amazing things to me about low carbing is that I no longer over-eat in response to stress.


washingtonpost.com
Grasping Why We Reach for a Taste of Calm


By Rob Stein
Washington Post Staff Writer
Monday, September 29, 2003; Page A16


When the going gets tough, the tough (and not-so-tough) often get hungry. Why that happens has been a mystery.

Although researchers have had clues that there might be some scientific basis for the notion of "comfort food," the precise link between stress and eating has been fuzzy.

Now, scientists have developed a model for a biological link between stress and the drive to eat: Food with lots of sugar, fat and calories appears literally to calm down the body's response to chronic stress.

In addition, research indicates that stress hormones encourage formation of fat cells, particularly the kind that are the most dangerous to health. That may be at least one reason why obesity rates are skyrocketing in the United States and many other modern societies.

"In highly industrialized countries, people do apparently seem to feel more stressed -- more under the gun," said Mary F. Dallman, a professor of physiology at the University of California at San Francisco, who outlined her theory in a paper to be published in an upcoming issue of the Proceedings of the National Academy of Sciences. "And they certainly are eating a lot more."

The new theory has been drawing praise from other scientists since it was posted on the Internet earlier this month.

"It's an important new model," said Alan G. Watts, a professor of neuroscience at the University of Southern California. "She's brought together under one roof two parallel processes. This is the first time anybody's been able to put together a united theory on stress and energy metabolism. It presents a new way of thinking about this."

While the relationship between stress and eating is driven by a complex mixture of emotional, psychological, social and physiological factors, the new research does appear to explain puzzles that have long baffled researchers, said Elissa S. Epel, an expert on stress, eating and fat at the University of California at San Francisco.

"There's a multitude of behavioral, attitudinal and psychosocial factors that determine whether humans engage in comfort eating. So it would be a real distortion to say it's all driven by the stress response," Epel said. "But this explains mysteries that stress researchers have been unable to resolve for a long time."

Scientists have long known that during times of stress, parts of the brain emit a chemical signal called corticotropin-releasing factor (CRF), which in turn causes the adrenal gland to pump out large amounts of hormones known as adrenal corticosteroids, including cortisol. These "stress hormones" flood the body, producing a wide array of effects designed to get ready to flee or fight: The immune system gets damped down. Alertness increases. Heart rate quickens. Activity jumps.

During acute stress -- a car accident, an argument -- a feedback system kicks in and shuts down this response fairly quickly. But during chronic stress, the system keeps going, caught in a vicious cycle.

To examine the relationship between chronic stress and food, Dallman and her colleagues conducted a series of experiments with rats, which are considered good models for how the same systems work in people. The researchers studied levels of stress hormones, brain activity and chemical signals, as well as fat distribution in the rats' bodies, comparing animals experiencing acute and chronic stress induced by exposure to cold or being restrained. The researchers also manipulated some animals' stress hormone levels by removing their adrenal glands, administering stress hormones or injecting them with the chemical signals that produce stress hormones.

When the rats were under chronic stress and had high levels of stress hormones coursing through their bodies, they became very active. They ingested large amounts of high-calorie lard, eschewing their normal feed, and drank prodigious amounts of sugar water. They ignored water containing saccharin, even though it tasted equally sweet. This, in turn, tended to make the rats develop deposits of fat cells in their abdominal areas. In humans, fat that gathers around the waist tends to increase the risks for various health problems.

"When you've got animals in the wild, or people in underdeveloped countries facing, say, a drought, they will turn on their adrenal corticosteroid system. That will make them run to get food and then they get food and eat and create stores of fat, which they need to do," Dallman said.

"It works beautifully when there isn't plenty of food around," she said. "But when there is plenty of food around, like in our society, where there's a McDonald's on every corner, it gets us into deep doo-doo, because this is the kind of fat that if it stays on is very bad for you. It's associated with diabetes and heart disease and stroke."

The fat cells, in turn, appear to send signals back to the brain, shutting down the production of stress hormones, which makes animals -- and people -- feel better and relax until they burn off those fat deposits. After ingesting high-sugar, high-fat diets, and developing fat deposits, the levels of CRF in the laboratory rats dropped.

But losing weight apparently reactivates the stress response system, starting the whole process again, said Norman Pecoraro, who works with Dallman.

"You're losing that metabolic signal to the brain that's calming things down. So you're removing that yourself by dieting. So one thing that's going to happen is that you'll feel more anxious and won't feel as good and you'll mount this compulsion system to go get the goodies," Pecoraro said.

Other researchers said that the work needs to be followed up with additional studies in animals and people.

"I think it's a fascinating new insight into this thing we refer to as comfort foods," said Bruce S. McEwen, a professor of neuroendocrinology at the Rockefeller University in New York. "Often what we call old wives' tales turn out to have a scientific basis, and this seems to be the beginning of understanding this old wives' tale."