The “obesity epidemic” is old news by now: 13 percent of the world’s adults are obese—defined as a body mass index of 30 or higher— including 36 percent of Americans, according to Harvard University. Among people in the U.S. under age 20, more than 19 percent are affected and the proportion is growing.

People forked out almost $225 billion in 2021 for help in dropping pounds, because losing weight is hard and the pounds that disappear have a way of returning.

Now researchers at Yale and Amsterdam universities think they know why.

It has to do with dopamine, the brain’s feel-good chemical.

In studying volunteers, the scientists found that the brains of obese people release less dopamine into the brain area controlling appetite after eating, compared to a control group of people of normal weight.

When your stomach takes in food, it sends a signal to the brain to release dopamine into that brain area to tell it that you’ve eaten enough and you don’t need to keep looking for more.

The stomachs of obese people seem to have trouble sensing the presence of nutrients, the study found. As a result, the stomach doesn’t send the “enough” signal to the brain so people no longer feel hungry.

When obese people in the study followed a 12-week eating plan and lost an average of 10 percent of their body weight, the lost weight returned in most participants when the plan ended. 

The returning pounds indicated that the belly-brain link had not been restored.

TRENDPOST: The study didn’t answer the question of whether the weak or absent gut-brain communication was a genetic trait. That would indicate that obesity might be an inherited tendency.

Scientists have just announced the discovery of a new genetic mutation that leads to insatiable hunger.

One issue not in doubt is the contribution to obesity by the Standard American Diet of burgers and fries, pizza, Cocoa Puffs, white flour, white sugar, Pepsi-Cola, feedlot-raised meats, and factory-made fats.

Sweets and simple carbohydrates give a quick sugar high, which sets up a positive feedback loop that keeps us reaching for a Snickers or bottle of Mountain Dew. That can turn a slender person into a supersize regardless of genetics.