Risky misuse of supplements was linked with low self-esteem, body dissatisfaction and gender role conflict.
The findings of their study were presented at the American Psychological Association's Annual Convention, held this year in Toronto, Canada.
While a significant amount of research has been carried out to assess the use of illicit anabolic steroids, much less attention has been paid to legal appearance- and performance-enhancing drugs such as protein powders and bars that are widely available.
"These products have become an almost ubiquitous fixture in the pantries of young men across the country and can seemingly be purchased anywhere and everywhere - from grocery stores to college bookstores," says study co-author Richard Achiro, of the California School of Professional Psychology at Alliant International University in Los Angeles.
Achiro believes that these products are being advertised in a manner that taps into an increasing objectification of the male body in society.
"The marketing efforts, which are tailored to addressing underlying insecurities associated with masculinity, position these products perfectly as a 'solution' by which to fill a void felt by so many men in our culture," he explains.
In the study, the researchers asked a total of 195 men aged 18-65 who had consumed legal appearance- or performance-enhancing supplements over the past 30 days to complete an online survey about their supplement use and other subjects relating to body image and masculinity.
Each participant also worked out for fitness or appearance-related reasons at least twice a week.
The researchers discovered that for many, the role of enhancement supplements was one that had become more prominent. More than 40% reported their use of supplements had increased over time, and 22% suggested that they had switched some of their regular meals for supplements not intended to be used as meal replacements.
Scale of supplement use a concern for 29% of participants
For some participants, their supplement use was becoming a source of worry. Around 29% admitted concerns with how often they used supplements, and 8% of participants suggested their physicians had recommended they reduced the amount they were using due to the risk of adverse health effects.
Achiro reports that 3% of the study's participants had been hospitalized as a result of supplement use contributing to kidney or liver problems.
The researchers concluded that the risky use of legal supplements correlated significantly with well-established indicators of recognized eating disorders, such as restrictive eating. They hope that their findings will put risky and excessive legal supplement use on the map as an issue that a significant number of men are faced with.
Misuse of the supplements appeared to be driven by multiple factors in the study, such as body dissatisfaction, low self-esteem and the perception that an individual is not meeting the strict expectations of masculinity in modern culture.
Achiro states that psychological factors driving body-conscious men to attain a level of physical or masculine "perfection" through using supplements in a way that has now been demonstrated as a form of eating disorder need to be examined further:
"As legal supplements become increasingly prevalent around the globe, it is all the more important to assess and treat the psychological causes and effects of excessive use of these drugs and supplements."
The US Food and Drug Administration (FDA) do not strictly regulate supplements. As a result, the strength, purity and safety of such products can vary, and health care providers should be consulted prior to beginning using new supplements.
Some studies have questioned the healthfulness of such supplements. Medical News Today reported on one study last year that suggested resveratrol supplements could impair the benefits of exercise, while another study published this year reported a link between muscle-building supplements and testicular cancer.