Physiology of Food CravingsGoing for the 3 Increases: Increase in Health, Increase in

Happiness & Increase in Energy

Strategies for Success in Weight ManagementBy: James J. Messina, Ph.D.

Key areas in a cross-section of the brain

Amygdala:controls emotion

Parts of the cortex: used for higher-order thinking in humans & send messages to the "central switchboard" that stimulates appetite

Food is far more than fuel to most of us

It’s tied in with our emotions, motivations Maybe even an ancestral impulse to store

energy for leaner times ahead In a study that could lead to more effective

treatments for obesity, researchers have traced brain impulses to show how appetite may be linked to higher-order processes such as emotion and judgment

The Researcher

In the Science March 2001 Issue: Jeffrey Friedman of Howard Hughes Medical Institute at The Rockefeller University and his colleagues describe a novel glow-in-the-dark technique that allowed them to see how cells within a mouse’s brain interact to send the “I’m hungry” signal to the rest of the body.

What we already knew

The body has a sort of fat thermostat, which regulates weight by influencing appetite, metabolism and other functions. Some people may be obese because their “set point” is too high. It’s also possible that obesity is on the rise because the thermostat mechanism evolved in an environment where food wasn’t as readily available as it is today.

What we already knew

A key component of the fat thermostat is the hormone leptin, which is produced mainly by fat cells and triggers neurons in the hypothalamus, the brain’s central switchboard for regulating conditions inside the body.

What we already knew

In general, an increased amount of fat leads to the production of more leptin, and vice versa. A change in leptin levels sparks a set of responses aimed at returning weight to the starting point, such as increasing or decreasing food intake.

What we already knew

When Friedman and other scientists first discovered how leptin regulates weight in mice, their findings raised hopes the hormone might be a long-awaited obesity treatment for humans but initial attempts at using leptin to reduce people’s weight met with limited success, however. One likely explanation is that leptin levels probably aren’t the only factors involved in the decision to start eating

What the new study explored

Friedman’s team wanted to know whether neurons that responded to leptin’s signal might also be in communication with neurons from other parts of the brain seemingly unrelated to feeding. “Feeding is a motivational behavior, not a reflex. We wanted to understand more about how the higher order and more basic neural systems talk to each other,” said Friedman.

What the Study found

Their findings indicate that the brain’s appetite-regulation system responds to additional signals, besides the simple “we need more energy” message that comes from fat cells. “Feeding strategies have developed by evolution. When an animal finds food, it has to decide whether or not to feed…”

What the Study found

“It’s going to take many factors into account, such as its own energy stores, its emotional state, the safety of the environment,”

“Our research suggests that many of the signals are sensed by key neurons in the hypothalamus.”

What their studying next

Friedman’s group now hopes to identify the type of neurotransmitter that’s carrying the additional signals from one neuron to another in the feeding pathway.