He's just a month shy of his sixth birthday, but Jack is already insecure about his body. At 40 pounds and 42 inches tall, he wears a size 3 and is the smallest kid in his class. He weighs himself several times a day: with his clothes on and then off, before and after meals, and even after he goes to the bathroom. His mind is consumed with getting bigger.

"At first, I thought it was just because he's a numbers guy," his mother, Heather, told The Huffington Post. "I thought, 'Oh, he's just doing it for the math.' But I started to notice it was more of an obsession with gaining weight."

Heather tried to tell her son that everybody has his own body type, that everybody's weight fluctuates. But each time he weighed himself, if he didn't gain weight or, even worse, if he lost just a quarter-pound, he would become visibly upset.

"Why am I less?" he would ask his mother desperately. "Why am I getting smaller?"

Last month, she finally decided to hide the scale and tell him that it was broken, but he hasn't stopped asking where it is.

Plus, he has started to focus on clothing size as a body metric. He's so self-conscious about the small size he wears that Heather puts labels over the tags on his clothes. She also lets him wear clothes that are too big for him, just to make him feel better.

There doesn't seem to be anything medically wrong with Jack's growth pattern, his mom said -- she's taken him to the doctor to be checked out. They're just small people in her family. And his insecurity doesn't seem to stem from any of the usual suspects, like bullying. Jack has frequent play dates, participates in soccer and baseball on school teams, and does well in class.

"That's the frustrating part. He's not having problems anywhere else. It's all internal," Heather said. "What is going on inside his head that he's so obsessed with his body?"

It was hard to gauge whether this was a problem, she said, until Jack broke down a couple of weeks ago, telling her that if his body is small, then his brain must be small. This, he cried, means he must not be smart.

"It breaks my heart," Heather said. "You can tell that there's something deep inside of him that he's anxious about."

The Problem Is More Common Than You Think

Despite public perception, body image issues and eating disorders are not exclusively female problems. The oft-cited figure is that about 1 in 10 eating disorders occur in males, but according to Raymond Lemberg, an Arizona clinical psychologist and expert in the area, newer research suggests that the real ratio is probably closer to 1 in 4. It wasn't until Harrison Pope, a professor of psychiatry at Harvard Medical School, published his seminal work around muscle dysmorphia, an obsession with bulking up also known as "reverse anorexia," in the late 1990s that researchers in the field began to pay attention to boys.

The biggest roadblock to widespread recognition of boys' body image problems is that the diagnosis guidelines haven't quite caught up, said Aaron J. Blashill, Ph.D., staff psychologist at Massachusetts General Hospital and an instructor at Harvard Medical School. Before the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders came out in 2013, for example, one of the criteria for anorexia nervosa was a loss of menses, something that's physically impossible for males.

"It was just harder in many ways for boys and men to meet those inclusion criteria," Blashill told The Huffington Post.

Eating disorders tend to manifest differently in girls and boys, although both are seeking to fit in with what they see as the societal ideal. Rather than wishing to be thinner, as young females often do, young males obsess over becoming highly muscular.

In the same way that girls are more likely to consider themselves overweight, even when they are underweight, studies have shown that boys are more likely to perceive themselves as underweight, even if they're actually overweight. Just like kids with anorexia, boys suffering from muscle dysmorphia will engage in extreme behaviors to reach their goals.

There are plenty of boys who long to be thin, too. Jennifer Hagman, a child psychologist and medical director of the eating disorders program at Children’s Hospital Colorado, said that 25 percent of her patients are boys, most of whom suffer from an atypical form of anorexia or food avoidance.

More often than not, eating disorders emerge close to puberty, but they can also develop in younger children. The youngest patient that Hagman has seen in her practice was just 5 years old.

"They [the younger children] aren't as likely as the teenagers to have an overt drive for thinness," Hagman told HuffPost. "They don't really know why they're refusing to eat enough to be healthy, but they have difficulty completing meals."

According to the medical experts, many young boys who develop eating disorders are perfectionists, harm-avoidant and intolerant of uncertainty. They may not be bullied about their bodies, but they're fearful of the possibility. Often, they show signs of anxiety, like a choking or vomiting phobia. While they may lack the language skills to talk about their bodies in terms of appearance, they express vague abdominal complaints.

"I think one of the big problems we have is that there's a stereotype of what eating disorders look like," said Alison Field, a professor of pediatrics at Harvard Medical School and a researcher at Boston Children's Hospital.

Body image issues often go unreported or undiagnosed for boys, the experts say, which may explain the varying statistics. Field published a study this year that found that nearly 18 percent of adolescent boys are concerned about their bodies and their weight. Among those boys, half wanted to gain more muscle and a third wanted to gain muscle and get thinner.

The results of that study, which looked at a series of questionnaires that teenage boys had filled out from 1999 through 2010, went beyond harmless vanity: The study found that the desire to bulk up was linked to future abuse of drugs, alcohol and muscle-enhancing supplements. Those seeking to be thinner were also more likely to develop depression.

While we may not hear about body image issues for boys as often as we do for girls, it seems that the ramifications are just as great. But knowing the statistics doesn't help parents understand why some boys are so worried about their physiques at such a young age.

Pop Culture Sends A Message To Boys

Just as girls do, boys are internalizing misguided messages about their bodies every day from seemingly harmless sources.

The desire that boys have to put on weight and muscle can be traced back to the 1964 debut of G.I. Joe, a toy that Lemberg told the The Atlantic was the male equivalent of the Barbie doll. All of those bulked-up action heroes, along with the brawny characters in many video games, present an anatomically impossible ideal for boys, much as Barbie promotes proportions that are physically impossible for girls.

Then there are the "real" bodies of models and celebrities that can also present an unattainably strapping paradigm.

"When you look at covers of 'health' magazines, like Men's Health, those guys are getting airbrushed and digitally enhanced," Blashill said. "They're selecting the 0.1 percent most attractive, most ripped guys for the covers and then enhancing them. Boys look up to these men."

According to the American Academy of Pediatrics, children consume about seven hours of media a day. Studies have shown that many boys are taking in those media messages and applying them to their own appearances.

At the click of a mouse or the tap of a screen, any child may stumble upon body-shaming content in mainstream media, from celebrity gossip to television shows. If Page Six can call Leonardo DiCaprio "The Great Fatsby," imagine how kids might use that as fodder for bullying on the playground.

"For boys, it's very difficult, because they can be teased for being small -- the social norms in society say that if you have bigger muscles, that shows that you're strong and very masculine -- and they can also be teased if they're overweight," Field said. "It's really either end of the spectrum."

From a very young age, boys are socialized to consider imperfect bodies "bad," according to Hagman, through such external influences as advertising and schools' misdirected attempts to counteract the obesity epidemic. The most common desire among the older boys she sees is to develop six-pack abs, something they hold up as the gold standard of masculinity.

In a 2002 focus group study, boys and men linked being fat with "weakness of will and lack of control" and blamed those who were overweight. Being lean and muscular, on the other hand, was associated with "feelings of confidence and power in social situations."

Hagman said that the social bias against body imperfection can be almost unavoidable for kids.

"We're all soaking in it, but when you're younger, you're much more vulnerable to those cultural pressures," she said. "You're trying to figure out who you are and what you should look like and what you should wear. You turn to the culture around you and what your culture tells you. In our culture, it’s 'Drive for a certain body type.'"

You Need To Look For The Problem

Blashill, Field and Hagman all agree there seems to be a perfect storm working against boys with body image issues: Stereotypes about what eating disorders look like, coupled with the difficulty many boys have in voicing their insecurities, lead doctors and parents to overlook the possibility of body dysmorphia or an eating disorder.

"I think there’s stigma in general for boys and men to talk about any psychological issues. And that's particularly a problem when it comes to what can be viewed as vanity or a feminine issue," Blashill said. "There can also be a high level of delusionality in that these boys don't think that it's a psychological issue. They think, 'I just need to be more muscular. The problem is with my body, not my mind.'"

Blashill advises looking at boys' behavior, rather than waiting for them to ask for help. Notice if your child gains or loses a significant amount of weight or if he changes his eating habits. Cutting out things like carbs or desserts could be a sign that your son is overly concerned about his size. If you pick up on any unusual behavior, don't be afraid to broach the topic.

"Try to understand why he wants those changes and help him understand all of the wonderful things about him that are not weight- and shape-related," Field said. "If there's a really valid reason that he wants to become bigger or stronger, help him come up with a healthy plan for doing that."

If you notice a problem, consult a pediatrician and be specific about your concerns, said Hagman. Many times, doctors don't have their eating disorder radars turned on with male patients, especially young ones. If there truly is a problem, family-centered intervention, rather than individual therapy, is the approach that Hagman and many of her colleagues favor. Parents and siblings will need to take an active part.

The good news is that it's usually much easier to treat body image issues and eating disorders if you catch them young, said Hagman, since little children generally still listen to their parents and will more easily take to behavioral programs.

This should be comforting to Heather, who has scheduled a checkup with Jack's pediatrician for next month. She plans to raise the issue then. For now, she's encouraging her son to focus on what he loves, like playing sports with his friends.

"Because he's small, he's not the fastest or biggest or strongest," she said. "But he's very passionate and he enjoys playing his little heart out."