As rates of obesity steadily rise in Australia, so too do those for non- alcoholic fatty liver disease. And, just like obesity, the disease is becoming more common in younger patients, causing alarm among the medical profession.
In 2011, 12.8 per cent of 17-year-olds in the Raine study - one of the biggest cohort studies in the world following participants from birth into early adulthood - had fatty liver disease: 16.3 per cent of females and 10.1 per cent of males.
Peak prevalence for the disease is usually among people in their 50s. 
The Gastroenterological Society of Australia estimates about 10 per cent of all Australians are affected.
Liver disease specialist Leon Adams, an associate professor from the University of WA school of medicine and pharmacology, said the liver was the prime organ involved in the metabolism of glucose and fats.
"When it is fatty, this metabolism is disturbed and that leads to insulin resistance and a susceptibility to diabetes in the future and also abnormalities in the cholesterol and lipid profile that increase the risk of heart disease and strokes," he said.
A fatty liver is closely associated with obesity, particularly central obesity, where there is a build-up of toxic visceral fat that flows into the liver. 
Patients who have type 2 diabetes or inherited liver disease can also be at risk.
In a small proportion of people it causes the liver to become toxic, causing inflammation and scarring with the potential to progress to cirrhosis and end-stage liver disease.
Professor Adams said the main culprit of fatty liver was diet. Those with the disease had been shown to have higher- calorie diets, where they ate higher amounts of saturated fats and simple sugars and less fibre and antioxidant vitamins.
"There's also good evidence to demonstrate that if in adolescence they have a dietary habit that is poor - full of junk food, processed meats - that increases the risk substantially of developing fatty liver disease as a late adolescent or young adult," Professor Adams said. 
"This demonstrates that bad dietary habits in our children are setting them on a life course trajectory of ill health."
Professor Adams said the build-up of fat in the liver could occur quickly, within weeks in extreme cases, but more usually across months and years in parallel with weight gain. 
The good news was that, unless it had already progressed to cirrhosis, fatty liver could also be cured in the majority of cases by lifestyle changes. 
Losing 10 per cent of your body weight by modifying diet and increasing exercise would reverse the condition for 90 per cent of people. 
But Professor Adams warned that was often easier said than done. 
"The actual process of getting people to lose 10 per cent of their body weight is more sophisticated than what you think."
Weight loss was unlikely to have an impact for those who had progressed to cirrhosis of the liver and a liver transplant might be the only option.
Amanda Lee, chairwoman of the Australian Dietary Guidelines Committee, said 
diet was now the number one contributor to the burden of disease in Australia and junk food was the biggest villain.
"It contributes to diabetes, cardiovascular disease, some forms of cancer - all of which are increasing in importance and having a huge drain already on our health resources, but that will increase into the future," she said.
Professor Lee, who was in Perth recently to support the launch of a new LiveLighter campaign to urge West Australians to reduce their junk-food consumption, said the average Australian spent more than half their food dollars on junk food.
For adults, over 35 per cent 
of energy intake was now coming from junk foods while for children it was over 41 per cent. 
"Those junk foods have a negative impact on our health but they also displace the healthier foods we are not eating enough of, so we need a radical diet change," she said.
Associate professor Leon Adams and professor Amanda Lee address the scourge of junk food and its impact on obesity and disease.