WA eating disorder experts are seeing more children and teenagers with one of two extremes - either starving themselves or becoming obese by binge-eating.
Associate Professor Sue Byrne, from the University of WA's department of psychology, said the number of adolescents with eating disorders had increased significantly and the age at which they were presenting was getting younger.
Professor Byrne, a speaker at an Australian Psychological Society conference in Sydney tomorrow, said there was growing evidence that parents dealing with the most dangerous eating disorder, anorexia nervosa, were better off using "tough love" or a zero tolerance to self-starvation.
She called for wider use of family-based therapy, which was often more effective than hospital-based treatment.
"We are seeing a 50-60 per cent rate of recovery in adolescents treated with family-based therapy and the relapse rates after one year and five years are much lower than with therapy that focuses on the individual only," she said.
Professor Byrne said family members were trained to deal with the child's disorder and take over responsibility for their eating and weight gain. In the past, many parents had taken a softer approach, not wanting to force the issue.
"If a child has anorexia nervosa, because of the illness he or she is unable to make good decisions about what they need to eat, so the parents have to take responsibility for making sure their child has enough to eat," she said.
"It's not the child's fault, because they have a serious illness, but it means meal times might take hours and be distressing.
"It's a bit like your child having leukaemia and needing chemotherapy, which can be a horrible treatment that makes them feel sick and their hair fall out, but you would make them do it if you knew they needed it to recover."
But Professor Byrne said binge eating in overweight people was now the fastest growing eating disorder and far more common than widely thought.
The University of WA is taking part in an Australian trial of three anorexia nervosa treatments in men and women aged 18 and over, who can have up to 40 free individual outpatient sessions with a psychologist. Phone 6488 7428.