Eating disorders among men remain highly underreported, even as experts warn that pressure to achieve a perfect physique is driving dangerous behavior. Brian Pollack, a licensed clinical social worker and certified eating disorders specialist, treats male patients at Hilltop Behavioral Health in Summit, New Jersey.

The warning follows Sylvester Stallone’s disclosure that he developed bulimia while preparing for his role in the 1982 movie “Rambo.” The actor, 80, told The New York Times that his eating habits became an “obsession” as he tried to look more “animalistic.”

Stallone said he drew inspiration from jaguars and cats while reshaping his appearance for the movie. “It became an obsession. Really bad. It got to the point where I became bulimic,” he said during the interview.

Bulimia nervosa involves episodes of binge eating, in which someone consumes a large amount of food while feeling a loss of control. According to the National Institute of Mental Health, those episodes are followed by purging behaviors that may include vomiting, fasting, excessive exercise or excessive use of laxatives or diuretics.

About 30 million Americans experience an eating disorder during their lifetime, according to the National Association of Anorexia Nervosa and Associated Disorders. Roughly one third of them are male, yet Pollack said eating disorders in men can look different and remain difficult to recognize.

Some men relentlessly pursue greater muscularity because they fear appearing weak, Pollack told Fox News Digital. Others seek an extremely lean, thin appearance and may severely restrict food or stop eating.

Pollack, who has not treated Stallone, compared current body image pressures affecting men and boys with beauty ideals imposed on girls and women during earlier decades. He said adolescent boys are consuming extensive information about society’s ideal version of masculinity.

“We’re seeing this extreme need for perfection and musculature — and that is leading to bulimia right now,” Pollack said. “It’s particularly in our adolescent boys, who are consuming a lot of information about the ideal of masculinity in the eyes of society at large.”

Expectations surrounding masculinity may also make it harder for men to identify or express vulnerability and distress, according to Pollack. He described bulimia as being closely connected to control, with purging used as a response to the loss of control experienced during a binge.

Celebrity appearances may further intensify the pressure. Pollack pointed to a trend called looksmaxxing, in which boys pursue an idealized appearance and may undergo cosmetic procedures intended to alter their jawlines.

“There’s a big trend right now called ‘looksmaxxing,' where boys are harming themselves in pursuit of an ideal appearance, including undergoing cosmetic procedures to alter their jawlines,” Pollack said. “It’s getting very scary out there, actually.”

Bingeing and purging usually happen in secret, making the disorder difficult for loved ones to spot. Pollack said some men hide the behaviors because they feel ashamed, while warning signs may appear through increasingly rigid exercise, eating and supplement routines.

A person may begin buying growing quantities of supplements such as creatine or performance enhancing substances such as human growth hormone. Other warning signs include exercising for multiple hours every day and carefully calculating nearly every part of a diet.

Some men become consumed by restrictive eating plans, including strict ketogenic diets, excessive protein consumption or diets limited to foods they consider clean. Those foods may include organic products, whole foods and non-GMO items, while foods prepared elsewhere may be avoided entirely.

Severe restriction may also contribute to binge episodes. Pollack said some people use cheat days to visit fast food restaurants and consume as much as possible, then hide in a bathroom within 45 minutes after eating.

Escalating laxative or diuretic use is another possible warning sign. Some people take increasingly large amounts when smaller doses no longer create the desired sensation of feeling emptied or in control.

Pollack stressed that bulimia and other eating disorders affect males across age groups, from middle school and high school through college and adulthood. “This is real, and men are afraid to talk about it,” he said. “There's a real issue.”

The consequences can be life threatening. Pollack said purging can cause electrolyte imbalances as well as kidney and liver damage, while prolonged malnutrition and repeated purging have caused severe heart damage and cardiac arrest in people he has seen.

Bulimia can also lead to severe erosion of tooth enamel and expensive dental treatment, Pollack said. Purging may contribute to esophageal problems, including acid reflux and GERD, while longer term complications can range from heartburn requiring over the counter medication to life threatening medical conditions.