University of Colorado researchers believe that fructose, a common sweetener found in table sugar and high fructose corn syrup, and used in a variety of prepared products, may be a major player in why Americans are packing on the pounds.

Fructose is a natural, simple sugar commonly found in fruits and honey. Table sugar and high fructose corn syrup are found in ketchup, molasses, baked goods, candies, soft drinks, and juices.  The scientists from the University of Colorado Anschutz Medical Campus theorize that fructose lowers and blocks the production of the body’s supply of adenosine triphosphate or ATP, a compound that naturally supplies energy to our cells. This results in a decrease in metabolism, so fewer calories from food are burned as energy.

Special: Doctor Discovers Sugar Control Method, Naturally

According to the New York Post, this shift can cause weight gain. The study, published in the journal Obesity, noted that fructose resets ATP to a lower level in the cells and suppresses mitochondria, which generate energy to power cells.

“Fructose is what triggers our metabolism to go into low power mode,” explained Dr. Richard Johnson, a leading expert in obesity and diabetes at the University of Colorado Anschutz Medical Campus and the lead author of the study, in a news release. Johnson says that his research clarifies the link between two hypotheses of obesity. One is that too much food, and primarily fat, drives obesity. The second is the carbohydrates-insulin model, which puts carbohydrates in the forefront of weight gain.

“Essentially, these theories, which put a litany of metabolic and dietary drivers as the center of the obesity epidemic, are all pieces of a puzzle unified by one last piece: fructose,” he said. While fructose slows metabolism and leads to loss of control of appetite, fatty foods become the major source of calories that drive weight gain.

Johnson likens the process to a bear preparing for hibernation. Bears eat fruit to prepare for the long winter ahead so that they can store fat. The fructose in fruit, a carbohydrate, keeps their energy levels low so they can store extra calories.

“This theory views obesity as a low-energy state,” he says. “Identifying fructose as the conduit that redirects active energy replacement to fat storage shows that fructose is what drives energy imbalance, which unites theories.”

Johnson says that his research offers a “full argument for how a particular carbohydrate, fructose, might have a central role in driving obesity and diabetes.

“We can trace it back to our ancestors, as well as learn from hibernating animals, exactly how fructose causes this ‘switch’ within us,” says the Post.