Diets high in fat can disrupt blood-sugar levels and trigger diabetes, researchers say in a study released this week.
Their findings help explain the link between obesity and a disease which is often linked to sugar.
Fatty foods can suppress an enzyme crucial to the production of insulin, which regulates sugar in the blood, according to scientists at the University of California at San Diego.
Obesity has long been linked to type-2 diabetes, the most common form of the disease in which the body does not make enough insulin, or cannot properly use it. Experts say obese people are up to 80 times more likely to develop diabetes, and both conditions are on the rise.
The new findings, published in the journal Cell, offer another explanation of exactly how the two are linked.
"We have discovered ... a molecular trigger which begins the chain of events leading from hyperglycaemia to insulin resistance and type-2 diabetes," said Jamey Marth, a professor of cellular and molecular medicine at the university.
"This finding suggests new approaches to the prevention and treatment of diabetes," said Marth, an investigator with the nonprofit medical research organisation Howard Hughes Medical Institute, which helped fund the research.
Marth and his colleagues studied the glycosyltransferase enzyme (GnT-4a), which helps the pancreas sense how much sugar is in the blood and release enough insulin to help process it.
In a study of normal mice that were fed a fatty diet, researchers found that the enzyme was repressed, leaving pancreatic cells unable to sense sugar levels and leading to diabetes.
"Our findings suggest that the current human epidemic in type-2 diabetes may be a result of GnT-4a enzyme deficiency," said Marth, adding that people who inherit a faulty gene that controls the enzyme may also be vulnerable to diabetes.
It may also play a role in the early onset of type-2 diabetes in children and teenagers, according to the study, which was also sponsored by the National Institutes of Health.
The researchers are now looking at ways to boost the enzyme in hopes of staving off diabetes.
Earlier this year, European researchers said they found a gene, called ENPP1, that helps control how cells respond to insulin.
In 11 different variations of the gene, six were linked to severe obesity, they reported.
Researchers at Beth Israel Deaconess Medical Centre in Boston have also discovered a substance called retinol binding protein (RBP4) that is released by fat tissue and can cause insulin resistance.
Their finding was reported in the journal Nature in July.