A potato (couch or not) in the diet adverse for diabetics.

Potatoes have a high glycemic index (GI) - meaning they cause a rapid, strong rise in blood sugar. Over time, these surges may damage the pancreatic cells that produce the hormone insulin, which is needed to metabolise blood sugar.

Overweight or sedentary adults may be particularly vulnerable to the effects of high-GI foods because they often have underlying insulin resistance - a precursor to diabetes in which body cells lose their sensitivity to insulin.

Thomas L Halton, the lead author of the new study found women with the highest potato intake were 14% more likely than those with the lowest intake to develop diabetes over 20 years.

Whole grains - as well as many high-fiber vegetables, fruits and legumes - have a lower GI than potatoes and white-flour products. Therefore the diet should have more of these than potatoes.