On Thanksgiving, many of us will eat a lot more than normal and then waddle away satisfied, with a turkey and sweet potato buzz.

Having a belly stuffed with cheering food can feel like a warm hug as of the inside.

Evolution has given us the instinct to eat a lot every time we can, preparing for hard times. It's the drive to survive, like puffy-cheeked squirrels storing up for the winter. It's as well fuelled by competition: beating the others to the food.

Our brains recompense us for it, by releasing pleasure chemicals -- in the same way as drugs and alcohol, experts say.

Scientists studying to facilitate that good feeling after eating call it intake analgesia, literally pain relief as of eating.

"There are reward circuits to make you enjoy eating," said Roger Cone, professor and chairman of molecular physiology and biophysics at Vanderbilt University. "If we didn't eat, we wouldn't survive."

The rewarding feeling ensured survival of the species.

"For most natural world and most of human olden times, we have not had excess of calories," Cone said. "Animals and humans had to work harder to survive. But now, with limitless calories everywhere for most people plus a great reduction in the amount of bodily activity, we've become obese."

In spite of the modern environment bombarded by appetizing ads and fast food, the wiring in the human brain hasn't altered. The reward circuits in the brain let loose chemicals that comfort and please.

Having such easy access to fat, salt as well as sugar is a recent development in the human being timeline, said Gary Wenk, writer of "Your Brain on Food." "Our bodies reward us big time for ingesting these kinds of things. When we find them, we eat them as much as possible because we believe we don't know when we'll see it once more. Cognitively, we know it's not true."

The body rewards fatty, salty, sweet foods by releasing endogenous opioids, which help control pain. A study available in Nature Neuroscience this year suggested that when rats consume these foods in great sufficient quantities, it leads to obsessive eating habits that resemble medicine addiction, the study found.

Even though eating as much as possible helped mankind survive in lean times, it is not so advantageous now.

Being full feels satisfying compared with the gnawing, rumbling hunger pains. Food replaces that emptiness with a sleepy, relaxing ease, which some of us know as food unconsciousness. It settles over the body as hormones are released and blood is unfocused to digestion, said Barbara Rolls, author of the "Volumetric Eating Plan," a diet plan based on feeling full, recognized scientifically as satiety.

"We start off feeling not good and irritable, then you eat and feel good," she said.

The body has natural cues to tell us to discontinue eating; it's a matter of whether we listen.

When food travels all the way through the stomach, it has to be digested to move into the upper little intestine. Once it gets to this division, the intestines release a hormone to tell the brain to stop eating at the moment, said Wenk, professor of psychology and neuroscience at Ohio State University.

Because food intake increases, the abdomen becomes full, the blood glucose levels change, and the hormone ghrelin, which stimulates appetite, calms down. That emotion of satiety should end the meal.

In spite of these cues, diners often pay no attention to them.

"Even when you're completely overfilled and you can't consume another bite, when something is delicious, you continue eating," Wenk supposed.

Rolls, a professor of nationwide science at Pennsylvania State University, has this advice: "I encourage people need to not eat as their meal is the last one."

Here are some instructions:

• Eat when you feel a slight hungry, but don't wait until you sense ravenous, because you'll probably overdo.

• Stop eating when you're enjoyably full.

• Try this exercise: Measure on a scale between one and 10 how you hungry you feel (with one as very famished and 10 as extremely full). Throughout the meal, periodically pause on the way to figure out where you are lying on this scale, and stop if you're at five.