The country's diet quality was given a rating of 61 on a 100-point scale when assessed using the CSIRO Healthy Diet Score – a scientifically validated survey which assesses people’s diet quality against the Australian Dietary Guidelines.
Discretionary food, or junk food, intake was found to be three-times higher than the recommended daily limit.
Based on the survey results, Australians eat the equivalent of 32kg of chocolate each year.
More than 40,000 people took part in the survey, which evaluated a person’s diet based on variety, frequency and quantity of the essential food groups as well as individual attributes such as age and gender.
According to Professor Manny Noakes, CSIRO Research Director for Nutrition and Health and the co-author of the CSIRO Total Wellbeing Diet, the results were concerning.
"The scores were fairly unflattering across all respondents," Professor Noakes said.
"If we were handing out report cards for diet quality - Australia would only get a C.
"While many people scored highly in categories such as water intake and the variety of foods consumed, there is certainly lots of room for improvement in other areas."
Discretionary or junk foods are foods and drinks that are high in sugar, saturated fats and/or alcohol and low in essential nutrients.
Of the survey responders, the average score received for the discretionary foods category was only 37/100.
"What we’re finding is people are having larger portions of junk food, more often," Professor Noakes said.
"This type of food is no longer just an indulgence, its become mainstream and Australians are eating it each and every day.
"In order to improve your diet quality, people need to cut back on the consumption of junk food, and start to focus on eating smaller portions.
"They also need to be more mindful of every bite they take by eating more slowly and consciously."
How do you measure up? The CSIRO Healthy Diet Score is a free 15-minute online assessment which evaluates diet quality and identifies areas of improvement.
"The online assessment provides Australians with a simple and trusted way of self-assessing the quality of their diet and how they compare to others of the same age, gender, generation, profession as well as people from the same State and across the country," Professor Noakes said.
"We would encourage people to take the test regularly to ensure they are improving their eating behaviour and overall health and wellbeing."
The online assessment can be completed at: CSIRO Healthy Diet Score.
Download a printable infograph of the Healthy Diet Score survey key findings PDF (211 KB).