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MOST Australian adults would need to change their diets drastically, eating much less potato and fatty foods and dispensing with junk food altogether to meet proposed Australian dietary guidelines.

The average Australian can match a lower intake of those foods with a big increase in greens, carrots, beans, nuts, fruit and fish to prevent the diseases of affluence, diabetes, cancer and heart disease, the National Health and Medical Research Council report states.

Consumption of potatoes by adults should drop by about 40 per cent of the current estimated average intake and high-fat dairy foods by 54 per cent, while consumption of legumes and low-fat dairy foods should rise by more than four times, the council says.

Amanda Lee, who chaired the expert group that produced the draft guidelines, says junk food, such as hamburgers, chips, pies, confectionery, soft drink and alcohol, now accounts for 35 per cent of adults' diets in Australia.

Yet one of the most important elements of the latest dietary analysis showed that most people who did not exercise vigorously, should not eat junk food at all if they were to meet the guidelines for a wholesome diet, Dr Lee said.

This was a change from the current guidelines developed in 2003 that allowed discretionary consumption of junk food.

Dr Lee said food choices were becoming increasingly significant to good health as evidence rose that consumption patterns were linked more directly with increasing or reducing the risk of cardiovascular disease, type 2 diabetes and several cancers.

A limited intake of foods high in saturated fat, sugar and salt, maintaining a healthy body weight, eating a wide variety of nutritious foods and choosing water as a drink ''will substantially reduce the risk of diet-related chronic disease and promote health and wellbeing in Australia'', the report says.

The proposed dietary guidelines, based on an analysis of the latest evidence on diet and health, show Australians should also be eating less white bread and low-fibre cereals and drinking fewer sugary drinks and alcohol, but more tap water.

Dr Lee said men should reduce their red meat on average by 20 per cent and give it to their daughters who should eat more red meat as a source rich in iron and zinc important to young women.

While latest research had shown a strengthening link between sweetened drinks and increased risk of excessive weight gain in children and adults, evidence has firmed that consumption of milk decreased risk of heart disease and some cancers.

Other beneficial foods included fruit linked to lower risk of heart disease, non-starchy vegetables to decreased risk of some cancers and wholegrain cereals to decreased risk of heart disease and excessive weight gain.

Dr Lee said this was the first report of its type internationally to review the evidence for food, dietary patterns and health in a holistic sense rather than focusing on particular nutrients.

''If we want to provide practical and realistic advice, we have to think about foods and dietary patterns, not nutrients,'' Dr Lee said.