It's not 'amount' but 'type' of fat that makes a difference to the scales

The findings by PhD student Barbara Brayner from Deakin University's Institute for Physical Activity and Nutrition (IPAN) are further evidence of the benefits of a diet high in unsaturated fats, such as those from nuts, seeds and avocados.

Ms Brayner said the research establishes a compelling case that eating certain types of 'unhealthy' fats increases people’s risk of developing obesity in later life.

For her research, Ms Brayner used data from the UK Biobank, a large cohort of people aged from 40 to 69 years living in the United Kingdom.

Ms Brayner followed more than 16,000 adults for an average of six years to understand if different fats led to different weight outcomes.

"We found adults who ate a diet higher in saturated fats, or 'unhealthy fats', from foods such as butter, high-fat cheese, red and processed meat and deep-fried foods were 24 per cent more likely to develop obesity," Ms Brayner said.

"Whereas people eating a diet higher in unsaturated fats or 'healthy fats', from foods such as avocado, nuts and seeds and olive oil were less likely to put on weight as they aged, even though they had similar kilojoule intake."

Ms Brayner said the Mediterranean-style diet was a good example of a dietary pattern that includes plenty of healthy fats, such as nuts and fish, and less red and processed meat.

"Snacking on a handful of nuts or seeds during the day, instead of a pastry or cake, is a great way to incorporate these healthy fats into your diet," Ms Brayner said. "Smashed avocado on toast instead of butter is also a great option."

In Australia, two out of three adults or 12.5 million people are overweight or obese.

Dr Katherine Livingstone from IPAN said the study was the first large scale look at the impact of fat type on developing obesity within the context of an overall diet.

"Most research to date has focused on single foods and nutrients. But diets are complex, and we don't eat foods and nutrients in isolation," Dr Livingstone said.

"We know that eating a diet high in kilojoules can lead to weight gain. However, not all fats have the same effect on our health.

"Our research helps address this confusion by considering the role of fat type and different foods, within the context of an overall dietary pattern," Dr Livingstone said.

The research published in The Journal of Nutrition was conducted using the UK Biobank Resource under Application 34894. Dr Livingstone is supported by a National Health and Medical Research Council Emerging Leadership Fellowship (APP1173803).