Gym rats may seem to be the picture of good health, but a new study suggests that many men who prioritize their workouts are abusing legal bodybuilding supplements to achieve their lean and muscular look.

More than 40 percent of men surveyed by researchers from the California School of Professional Psychology in Alhambra said they had increased their use of supplements such as protein bars, creatine powder and glutamine capsules over time. The researchers said they were alarmed to discover that 29 percent of the men acknowledged that their use of the supplements might be damaging their health.

The findings, presented Thursday at the American Psychological Association’s annual meeting in Toronto, should put risky supplement use “on the map” as an eating disorder that affects “a significant number of men,” study leader Richard Achiro said in a statement.

The supplements are “widely available in grocery stores, nutritional food outlets and college bookstores,” Achiro and his co-author Peter Theodore wrote in a summary of their research findings. The products “are marketed specifically toward men hoping to achieve an ideal ratio of fat to muscle,” they said.

To see whether they were fueling eating disorders in some men, the pair surveyed 195 men older than 18 who said they worked out at least twice a week and had used some type of legal supplement in the previous 30 days.

The results revealed that 22 percent of the men said they had used the supplements as meal replacements, even though they’re not designed for that. In addition, 8 percent of the men had been told by a doctor that they should cut back on their supplement use or stop taking them altogether, and 3 percent said the supplements had caused kidney or liver damage severe enough to land them in a hospital.

The survey responses also gave some clues about who was most likely to abuse the legal supplements. Men who had body dissatisfaction and low self-esteem were more likely to report using the pills, powders and protein bars, the researchers found. So were men who most internalized the cultural ideal of male bodies as lean and muscular and those who held traditional views about masculinity that were so rigid they caused distress.

“Excessive legal APED (appearance- and performance-enhancing drugs) use may represent a variant of disordered eating that threatens the health of gym-active men,” the researchers concluded in their report.