They might make you fat, but at least potato chips, sweets, packaged biscuits, sugary breakfast cereals – not to mention those hamburger parties and pizzas in the freezer! – are happy foods, right?

Maybe not.

A somewhat alarming study from Deakin University has found that the risk of depression significantly increases among Australians consuming more 30 per cent of their daily diet as ultra-processed foods.

The findings are supported by previous research that found links between ultra-processed foods and mental health more broadly.

How many people are affected?

According to a previous Deakin study, ultra-processed foods represent 38.9 per cent of total energy intake in the average Australian diet. That’s a lot of chips and crackers.

That study focused on the link between the uptake of processed foods and the prevalence of obesity in Australia, which has risen dramatically over the past 20 years – from 19 per cent in 1995 to 31 per cent in 2018.

Australia has the fifth-highest rate of obesity among the Organisation for Economic Co-operation and Development countries.

The new study

Corresponding author Dr Melissa Lane, from Deakin’s Food and Mood Centre, said the results “provide further evidence of the wide-ranging harms of diets loaded with cheap, well-marketed but often nutrient poor convenience foods”.

Ultra-processed foods (UPFs) are not limited to typical junk and fast foods.

They also include mass-produced and highly refined products that might be considered relatively ‘neutral’ or even ‘healthy’ – like diet soft drink, some fruit juices and flavoured yoghurts, margarine, packet preparations of foods like scrambled egg and mashed potato and many ready-to-heat and-eat pasta dishes.

Dr Lane and colleagues examined the associations between ultra-processed food consumption and depression in more than 23,000 Australians from the Melbourne Collaborative Cohort Study.

“Australians who ate the most ultra-processed food had about a 23 per cent higher risk of depression compared to those who ate the least amount,” Dr Lane said.

Progress followed for 15 years

The study participants – who initially weren’t taking any medication for depression and anxiety – had their intake of UPFs measured at baseline.

As they were followed over 15 years, their psychological distress was measured and taken as an indicator of depression.

“Even after accounting for factors like smoking and lower education, income and physical activity, which are linked to poor health outcomes, the findings show greater consumption of ultra-processed food is associated with a higher risk of depression,” Dr Lane said.

Being an observational study, it didn’t confirm ultra-processed food as a causal factor for depression. But it underscores an association with a higher risk.

 Inflames the brain, evidence of memory loss

Randomised clinical studies are needed to confirm these links. Some hard evidence of the impact these foods have on the brain is emerging.

One study, as we reported in 2021, found that it takes just four weeks for a diet of highly processed food to inflame the brain and elicit behavioural signs of memory loss.

This was a study done with older rats, with a focus on how a poor diet impacts ageing brain tissue and functioning. Research has shown that rat and human brains are remarkably similar in structure and function.

The study diet mimicked ready-to-eat human foods that are often packaged for long shelf lives, such as potato chips and other snacks, frozen entrees like pasta dishes and pizzas, and deli meats containing preservatives.

Maybe that’s why they call it fast food

“The fact we’re seeing these effects so quickly is a little bit alarming,” said senior study author Dr Ruth Barrientos, a behavioural neuroscientist researching the role of inflammation on cognitive impairments at Ohio State University Institute.

“These findings indicate that consumption of a processed diet can produce significant and abrupt memory deficits.”

A moving problem for children

Last year, we reported on research that found children aged three to five who eat more highly processed foods – such as chicken nuggets, frozen pizzas and sugary breakfast cereals – have poorer locomotor skills than children who eat less of these poor-quality foods.

Chicken nuggets are among the foods that hinder movement skills of little kids. Photo: Getty

Locomotor skills include walking, running, jumping, hopping, crawling, marching, climbing, galloping, sliding, leaping, hopping and skipping.

These skills enable children to move through different environments and, while some of them of these skills might need to be taught, they serve as developmental markers.

The implication here is that kids with poorer motor skills are likely to end up fat and unhealthy.

Indeed, the study, from Sacred Heart University in Connecticut and the American Society for Nutrition, found “lower cardiovascular fitness in 12- to 15-year-olds who consumed more ultra-processed foods”.

Heart attack central

In 2021, we reported on a devastating study that found if you’ve already suffered a heart attack, and continue eating too many ultra-processed foods, you’re at 66 per cent greater risk of having a second heart attack or stroke.

And this one will likely kill you.

But you’re eating all that salmon, right? Too bad.

The study found that “even in people generally following the Mediterranean diet, but consuming too many ultra-processed foods, health risks are higher”.