It seems Australians have a big sweet tooth, with one third of us admitting to eating too much junk food.

One third of Australians eat too much junk food, with a nation-wide survey confirming our eating habits are well below par.

Just one per cent of people are avoiding junk food, according to the 2016 CSIRO Healthy Diet Score report.

"We find that there is often a tendency to under-report on certain types of food, so in all likelihood that figure is even higher," said Professor Manny Noakes.

The CSIRO report showed that construction workers were among those with the poorest diets, while public servants, real estate agents and health industry workers reported some of the healthiest eating patterns.

Women also have better nutritional levels than men.

Researchers at the CSIRO canvassed the dietary habits of more than 86,500 adults across the country over a 12 month period and found four out of five Australians have a below par diet.

Overall the nation was awarded a diet score of 59 out of 100.

The closest we get to meeting Australian Dietary Guidelines is the fruit food group where 49 per cent of respondents meet the recommended intake.

Prof Noakes says Australia has an image of being fit and healthy but this is not so and people need to act now to improve their diets to better fight the battle against obesity and Type 2 diabetes.

"If we can raise our collective score by just over 10 points, we help Australia mitigate against the growing rates of obesity and lifestyle diseases such as heart disease, Type 2 diabetes and a third of all cancers," Professor Noakes said.

"All people need to do is halve the bad and double the good. In other words, halve the amount of discretionary food you eat and double your vegetable intake."