United States medical researcher Neal Barnard says he makes no apologies for promoting a vegan-style diet in New Zealand whose farmers rely on the world eating meat and dairy foods for their livelihood.
Dr Barnard, in Wellington to address Victoria University students, told NZPA that obesity and "terrible" eating habits increasingly meant that people in affluent countries were facing a rising tide of adult-onset diabetes and premature deaths.
People with type-2 diabetes - a result of a combination of genetics and poor eating and exercise habits - ran a high risk of heart disease, stroke, kidney failure, blindness and limb loss.
He said meat-based diets were a problem in the US, where individual meat consumption had gone up from an average 68kg a year to 93kg, and cheese consumption has risen from 2kg to 15kg a head.
He compared unhealthy foods with modern attitudes to cigarettes, suggesting that junk food should carry warning labels about diabetes.
Dr Barnard said that fat build-up inside muscle cells interfered with signalling by insulin inside the cells and their ability to "burn" fat.
His research showed that type-2 diabetics could "repair" their insulin function by cutting meat and dairy from their diet, and slashing their intake of food oils.
"The low-fat vegan diet is more effective at treating diabetes than the typical diet or oral medications," he said. "I want people to stop focusing on how much pasta, how much glucose, and how much rice they eat. Instead, I want to take the grease out of the diet. This approach could put a huge dent in the diabetes epidemic."
Over 175,500 New Zealanders have congenital diabetes (type-1) or the adult-onset form (type-2). Dr Barnard described the illness as "the disease of our time".
"In the US, one third of all children born since 2000 will develop diabetes," he said.
People who ate a low-fat vegan diet - cutting out all meat and dairy products and slashing their intake of vegetarian oils - could lower their blood sugar levels more and lose more weight than people on a standard American Diabetes Association diet, said Dr Barnard. Though he is promoting his book the Reverse Diabetes Diet, Dr Barnard said he was not promising everyone following the diet could be cured, but that blood sugar levels could be reduced, and insulin resistance turned around.
Vegan dieters could lower their cholesterol more and end up with better kidney function, and the vegan diet was easier to follow because it did not involve counting calories or portion control.
"What really happens is a change in energy density: you get foods low in fat - fat has nine calories per gram while carbohydrate has only four grams - and all the fibre fills you up."