Adolescents who see themselves as puny and who exercise to gain weight may be at risk of so-called muscularity-oriented disordered eating behaviors, say researchers led by UCSF Benioff Children's Hospitals.

The researchers found that 22 percent of males and 5 percent of females ages 18-to-24 exhibit these disordered eating behaviors, which are defined as including at least one of the following: eating more or differently to gain weight or bulk up, and use of dietary supplements or anabolic steroids to achieve the same goal.

Left unchecked, these behaviors may escalate to muscle dysmorphia, characterized by rigid diet, obsessive over-exercising and extreme preoccupation with physique, say the researchers in their study publishing in the International Journal of Eating Disorders on June 20, 2019.

"Some eating disorders can be challenging to diagnose," said first author Jason Nagata, MD, of the UCSF Division of Adolescent and Young Adult Medicine. "Unlike anorexia nervosa, which may be easily identified by parents or pediatricians, disordered eating to increase bulk may masquerade as healthy habits and because of this, it tends to go unnoticed."

Heart Failure, Depression, Social Isolation in Worst Cases

At its most extreme, it can lead to heart failure due to insufficient calories and overexertion, as well as muscle dysmorphia, which is associated with social withdrawal and depression, Nagata said.

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The 14,891 young adults in the study, who came from throughout the United States, had been followed for seven years. The researchers wanted to see if the early data, when the participants' average age was 15, revealed something about their perceptions and habits that may serve as warning signs.

They found that boys who exercised specifically to gain weight had 142 percent higher odds of this type of disordered eating; among girls, the odds were increased by 248 percent. Boys who perceived themselves as being underweight had 56 percent higher odds; in girls the odds were 271 percent higher. Smoking and alcohol use in boys, and smoking in girls, increased odds moderately.

Additionally, being of black race bolstered odds by 66 percent in boys and 181 percent in girls.

Non-heterosexual identity, which the participants had been asked about when they reached adulthood, was not found to be a risk factor, the researchers said.

In young adulthood, 6.9 percent of males reported supplement use to gain weight or build muscle and 2.8 percent said they used anabolic steroids. Use by young women was significantly lower at 0.7 percent and 0.4 percent respectively.

"Supplements are a black box, since they are not regulated," noted Nagata. "In extreme cases, supplements can cause liver and kidney damage. Anabolic steroids can cause both long-term and short-term health issues, including shrunken testicles, stunted growth and heart disease."

Nagata said that clues that indicate behaviors may approach muscle dysmorphia include a highly restrictive diet that omits fats and carbohydrates, compulsive weighing and checking of appearance, and extensive time dedicated to exercise that may cut into social activities.

Co-authors: Senior author is Scott Griffiths, PhD, of Melbourne School of Physiological Sciences, University of Melbourne, in Australia. Co-authors are Stuart B. Murray, PhD, Kristen Bibbins-Domingo, PhD, MD, MAS, and Andrea Garber, PhD, RD, of UCSF; and Deborah Mitchison, PhD, of Macquarie University and Western Sydney University, in Australia.

Funding: Nagata is a participant in the Pediatric Scientist Development Program funded by the American Academy of Pediatrics and the American Pediatric Society; Murray was supported by the National Institutes of Mental Health; Garber was supported by the National Institutes of Health; and Griffiths is supported by a National Health and Medical Research Council Early Career Fellowship and a University of Melbourne Early Career Grant.