Nutritionists are lamenting the decrease in Australians' consumption of beneficial whole grains as a result of new dieting trends.

Australians are increasingly giving up whole grains as part of new dieting fads, despite their health and weight benefits.

Consumers last year ate 29 per cent fewer core grain foods than in 2011, while six per cent did not eat any at all.

The results of the 2014 Australian Grains and Legumes Consumption Study, which canvassed the habits of more than 3000 people aged between two and 70 years, were presented at a Sydney symposium.

Trends such as the low-carb high-fat diet, the Paleo diet and a mainstream shift to gluten-free diets had led to the decline, said dietitian Michelle Broom, general manager of the Grains & Legumes Nutrition Council.

"Fad diet trends have resulted in widespread confusion about the benefits of eating core grain foods and legumes," she said.

"We need to educate people about the health consequences of cutting these nutritious foods out of their diets."

Nutritionist Dr Rosemary Stanton told AAP the results supported other evidence that people were eating less whole grains.

"It's a bad thing because a lot of long-term, good studies show that consumption of whole grains is associated with a low incidence of heart disease, type 2 diabetes and weight gain," she said.

Ms Broom said Australians were buying into the idea of a quick fix to losing weight by radically changing their diet.

"While this may seem to be a more appealing preposition than the age-old messages of balance and moderation, these people are missing out on the health benefits of grains," she said.