This compares with 68per cent of men and 55per cent of women overweight or obese in 2007-08.

The biggest health impact of increasing girth comes in soaring rates of type 2 diabetes. But being overweight also increases your risk of heart disease, high blood pressure, some cancers, respiratory conditions, gall bladder disease, incontinence, fatty liver disease and more, according to the guidelines, released on February 18 by the National Health and Medical Research Council.

If you are obese with a BMI of 30-35 (which means weighing 77kg or more if you are 160cm; and 97kg or more if you are 180cm), your life expectancy is reduced by two to four years. For a BMI over 40, take eight to 10 years off your life.

In 1995, adults were eating 350 kilojoules a day more than a decade earlier. The change was even more dramatic for children aged 10 to 15, with girls eating 900 kilojoules a day more than girls a decade before and boys eating an extra 1400 kilojoules a day.

The increase is driven largely by sugary drinks and sweets, and the likes of biscuits, pies, pizza and desserts.

It’s a state of affairs that nutritionist and member of the panel that reviewed the guidelines Dr Rosemary Stanton blames on the food industry for skewing messages on food, and governments for not taking action. “It’s up to the health ministers, and frankly they’re not prepared to stand up to the huge forces working in the other direction,” she says. “People really make a fuss if you suggest that people should have less of any of their products.”

Stanton, who herself confronts pressure from sectors of the food industry to boost consumption recommendations for their products, urges health ministers to “get a bit of courage”, starting with a ban on junk-food advertising to children.

“Thirty-six per cent of kilojoule intake is coming from junk food; 41per cent for children. So are we really surprised that people are getting fatter?” she says. “They’re cutting back on vegetables, wholegrains are coming down in consumption, and kids are drinking soft drinks instead of milk.”

Despite the alarming figures on weight and the clear advice to eat less and exercise more, the guidelines are not as strong as you might expect on links between specific foods and specific diseases. But the council says the evidence has strengthened for:

■ fruit lowering your risk of heart disease

■  vegetables lowering your risk of some cancers

■ wholegrain cereals lowering risk of heart disease and weight gain

■ milk lowering risk of heart disease and some cancers

■  sugary drinks causing weight gain.

The guidelines rank evidence according to whether it shows a “convincing association” between a food and a disease, or a probable or a suggestive association. Most links are suggestive only, except in the case of heart disease and stroke where links are firmer. Stanton says to get the highest evidence rating you need a double-blind randomised control study, which you can’t do in the case of food. When it comes to cancer, the complexity of the disease makes it more difficult still to get conclusive evidence. “What we did was look at 55,000 pieces of evidence, and unless we could find five good quality studies [for a particular claim] we didn’t consider it evidence.”

The council found vegetables and fruit probably reduce your risk of heart disease and stroke.  Wholegrains  also probably reduce your risk of heart disease and type 2 diabetes.

Fruit and vegetables have a suggestive link with fewer mouth and throat cancers (although preserved vegetables increase the risk).

The evidence suggests tomatoes reduce your risk of prostate cancer, cruciferous (the cabbage-type) vegetables reduce your risk of lung cancer, and spinach reduces the risk of colorectal cancer (although it’s very specific; the evidence suggests no protection from this cancer from cruciferous vegetables, carrots, potatoes, beans and lentils).

Red meat, though, probably increases your risk of colorectal cancer if you eat more than 100grams to 120 grams a day, and has a suggestive link also to renal cancer.

Fish, though, is suggested to lower risk of heart disease and stroke, and probably reduces your risk of dementia.

And fat is making something of a comeback. Rather than banning fat from your diet, you are urged to replace saturated fat (in biscuits, pies, pastries and the like, as well as butter, cream, coconut and palm oil) with polyunsaturated and monounsaturated fats such as oils, avocado and nut butters.

The advice to switch  to unsaturated fats is not without its critics, notably Queensland writer David Gillespie, who today releases a book called Toxic Oil, in which he blames polyunsaturated fats (in much processed food and in most vegetable and seed oils) for a host of diseases.

But Stanton rejects Gillespie's view as extreme, and says his linking of seed oils with disease is wrong. She says the simple message on fat is to limit your intake if you're trying to control your weight because it is high in kilojoules.

"We're just trying to correct the really strange message that people picked up. The fat message was so distorted by the food industry. The fat message was cut the fat off your meat, skim some of the cream off your milk, and don't have lots of fried stuff. But the message people got, and I think this was engendered by the food processing industry, was that you can eat anything as long as it was low fat. And what we got was literally thousands of low-fat products where the fat was replaced by sugar or refined starches … and people started not eating nuts and thinking avocado was a bad food."

While the guidelines don't encourage you to eat butter, the message is clear on the benefits of milk, yoghurt and cheese (especially milk), which probably lower your risk of heart disease, stroke, high blood pressure and colorectal cancer, and are suggested to decrease your risk of type 2 diabetes. While dairy has been claimed to cause breast cancer, the council says evidence suggests that consuming one serve a day of dairy food does not increase breast cancer risk. Nor does dairy food such as milk increase your risk of weight gain.

Stanton says butter is usually studied with other saturated fats (the panel prefers to talk about foods than ingredients, since fat is included in a wide variety of good and bad foods), and is linked to blood cholesterol, which in turn is linked with heart disease. She says when people claim the health benefits of saturated fats, they're using studies that compare eating a diet high in saturated fat with eating a diet high in sugar and starches - and there is no benefit at all in making the switch to a that kind of diet.

As for alcohol, it probably protects against heart disease (at a rate of one drink a day for women and up to two for men), but probably also increases your risk of breast cancer (even at 10 grams a day, which is about 100 millilitres of wine; a restaurant pour is about 150 millilitres, or 1 ½⁄ drinks), as well as cancer of the esophagus and mouth, and is suggested to increase risk of colon cancer and liver cancer, even at very low levels.

The guidelines play down the recent focus on glycemic index, saying while lower GI diets might help manage diabetes, they're not going to help you lose weight.

The new guidelines say 30 minutes a day of exercise is not enough, as previously thought. You need to do 45 to 60 minutes a day of moderate-intensity exercise to avoid gaining weight (and if you have been obese, at least 60 to 90 minutes). Moderate is exercise that increases your breathing and heart rate slightly, such as brisk walking (at a speed where you can talk but not sing), medium-paced swimming or cycling.

What you should eat

■ Double intake of diary - but eat less full-fat dairy and more low-fat varieties. Adults should have 2½⁄ serves a day (a serve equal to a cup of milk, three-quarters of a cup of yoghurt, or 40 grams of cheese).

■ Eat two serves of fat a day, if you're female, and four serves if you're male. Swap saturated fats for unsaturated spreads and oils. A serve equals just seven grams of oil (about a teaspoon).

■ Boost your consumption of vegetables by 30 per cent, to five serves a day for women and six for men; a serve of vegetables is 75 grams (half cup cooked vegies, one cup raw); a serve of fruit is 150 grams (one piece, or two for small fruits such as plums).

■ Eat more wholegrain and high-fibre cereals (160 per cent more) and less refined cereals (30 per cent less). Adults should eat six serves a day (a serve is a slice of bread or half a flatbread, half a cup of cooked rice, barley etc).

■ Eat 40 per cent more fish, poultry, eggs, nuts, seeds, legumes and beans. Men should eat 20 per cent less red meat. Women should eat 2½⁄ serves of these foods, including meat, a day; and men should eat three serves (a serve is 90 to 100 grams of raw meat, half a cup of mince, 100 grams of chicken, 115 grams of fish, two eggs, and a cup of cooked beans).

The guidelines are at nhmrc.gov.au.