The war against the obesity epidemic is on, with more than two in three adults in the U.S. being considered overweight or obese. In the latest scientific battle, researchers had six men gorge themselves for a week in the hopes of finding how, why and when chronic overeating leads to metabolic problems and to Type 2 diabetes.

All the investigators needed to spot what they were looking for, and it’s likely cause, though, took effect in less than three days.

By the second and third day of the study and participants’ consumption of 6,000 calories — more than double their usual caloric intake — researchers could detect the onset of insulin resistance.

The indisputable cause of their insulin resistance was the sudden onset of their gluttonous diets. More specifically, researchers found that their bodies’ efforts to manage the sudden caloric assault forced the mitochondria in their cells to unleash a flood of oxygen byproducts that are toxic to nearby cells.

“Mitochondria are energy engines and when they’re flooded with calories they become leaky and release [chemicals] and cause oxidative stress,” Dr. Kevin Niswender, associate professor of medicine at Vanderbilt University Medical School in Nashville, Tennessee, explained to ABC News.

Oxidative stress could lead to inflammation and other problems down the line. It could also affect certain proteins that can lead to insulin resistance, a condition in which cells fail to respond to insulin, causing the pancreas to produce more insulin to keep with the difference.

Insulin resistance can lead to two things: high concentrations of glucose remaining in the blood — which damages nerves and blood vessels — and an overworked pancreas.

The study, which was published in the journal of Science Translational Medicine, suggests antioxidant therapies, such as Vitamin C and E supplements, coenzyme Q10 or selenium, could help patients who overeat from developing metabolic problems in order to target the cells that have become insulin resistant.