Researchers single out exercise, diet

Research suggests a combination of exercise and changes of diet could dramatically cut many New Zealanders' chances of getting diabetes or heart disease.

Otago University believes the research, claimed as a world first, could help reverse the epidemic of diabetes both in New Zealand and internationally and significantly reduce heart disease.

"The unique aspect of our study is that we targeted otherwise healthy people who do not make insulin properly but have not yet developed diabetes," said research team leader Dr Kirsten McAuley, of the university's human nutrition department.

Lifestyle changes were known to have a beneficial impact on people who already have diabetes.

"Poor insulin sensitivity means the body produces insulin but the insulin is not able to do its job properly," Dr McAuley said.

"The problem could affect up to 25 per cent of the New Zealand population, and is a major risk factor for diabetes and heart disease."

Insulin is a hormone produced by the pancreas in varying amounts, depending on the level of glucose (sugar) in the blood.

The hormone prevents a buildup of blood glucose and ensures that various tissues have enough glucose.

The study of 79 people aged between 35 and 60 suggests a combination of intensive exercise and changes to diet could prevent or dramatically reduce the risk of adult-onset diabetes (known as type 2 diabetes) and heart disease.

Volunteers who followed exercise and diet guidelines increased their insulin sensitivity - the ability of their bodies to use insulin properly - by about 20 per cent.

An additional group of 36 Maori also included in the study showed a similar improvement.

Heart disease is New Zealand's number one killer. But type 2 diabetes has now reached epidemic proportions, affecting up to 20 per cent of Maori and six per cent of the rest of the population.

The Ministry of Health estimates that over the next 20 years, the prevalence of type 2 diabetes will increase by 109 per cent for Pacific Islanders, 90 per cent for Maori and 39 per cent for the remainder of the population, putting a huge strain on the health system.

Over four months, the researchers studied three groups - a control group, a "modest"group who followed common diet and exercise guidelines for general health, and an "intensive" group who were given specific advice on diet and exercise.

The aim of the innovative study - it won Dr McAuley the Young Investigator Award at a recent international nutrition conference in Vienna - was to compare the groups to see if the degree of lifestyle changes made a significant difference to their insulin sensitivity and risk of developing diabetes and heart disease.

"The key finding was that insulin sensitivity didn't improve significantly in the 'modest' group, but in the 'intensive' group there was an improvement of anywhere from 16 to 23 per cent in insulin action," Dr McAuley said.

" It looks as if we need to target dietary change and exercise more specifically to get the real benefit.

"The results suggest that if people follow the guidelines developed for the intensive group, before they develop impaired glucose tolerance [the next stage], then their chances of developing diabetes and heart disease may be reduced significantly.

"Even if the onset of diabetes could only be delayed, rather than prevented, there would be major health benefits.

"Once you've got diabetes and have had it for a few years, you start getting complications such as heart trouble, eye, kidney and foot problems - so the longer you've got it the more likely you are to have problems."

Professor Jim Mann, diabetes expert and head of the human nutrition department, said the findings could be a step forward in the battle against diabetes and heart disease.

"Diabetes is clearly the major epidemic in New Zealand in the 21st century, and this research gives us important clues on how to reverse it."

Dr McAuley says the next stage of the research is to see if the study participants can maintain these changes over a period of up to 18 months.

A human nutrition masters student, Kelly Whiteford, has started the follow-up study.

Another move, which is part of the study, is a community-based programme to prevent or delay the onset of type 2 diabetes in Maori.

Eleanor Murphy, Maori diabetes health worker at Dunedin Hospital, says that while the data has yet to be fully analysed, there appear to be similar benefits to the clinical trial in terms of improved insulin resistance, reduced blood pressure, lower cholesterol levels and, to a lesser extent, weight loss.

* The study is being financed by the Health Research Council of New Zealand, Novo Nordisk, the University of Otago and the Otago Diabetes Research Trust.