Geri Halliwell was on top of the world in the 1990s as Ginger Spice, the most visible member of the Spice Girls. But Halliwell recently revealed that the pressures of stardom had a negative effect on her body image and mental health and that she suffered from bulimia, a disorder that went unnoticed because she didn't experience a noticeable weight change.

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Halliwell engaged in "comfort eating," binging, and purging, all of which are signs of bulimia, she revealed in a new episode of OWN's "Where Are They Now?" "I started being bulimic, and no one would notice it, because your body weight stays pretty much the same," she said, according to Shape. "It's bloody dangerous. I was worried I'd get fat. I would binge and then felt fatter and would make myself sick. It was awful."

Halliwell's revelation highlighted a little-known fact about eating disorders: A person's physical appearance is not always an indicator that he or she has an eating disorder.

People with eating disorders don't necessarily have physical characteristics that signal the disorder, Claire Mysko, chief executive of the National Eating Disorders Association, told ATTN:

"I would say that it is very common for people who struggle with eating disorders to not be visibly underweight or overweight. ... Someone could be at a weight where you wouldn't necessarily notice on the surface that something is wrong, but they could be really, really struggling with very severe eating disorder symptoms.

"Weight loss is not necessarily associated with eating disorders. Certainly, with some — and with anorexia — that is a sign. [But for] most people who struggle with eating disorders, you wouldn't necessarily know it from looking at them.

"Anorexia is associated with restriction of food; as a result, the weight loss is associated with it. Bulimia is characterized by binging and purging, so compensatory behavior like vomiting or taking laxatives or, sometimes, extreme exercise can be a form of purging for those who struggle. The process is different in the body, and I'm not a medical doctor, but certainly it's not the same as what you would see with anorexia.

"With binge-eating disorder, that's associated with eating a large quantity of food in one sitting. It's accompanied with feelings of a lot of shame and guilt, but you don't have the purging behaviors."

Stereotypes about what a person with an eating disorder is supposed to look like don't "match up with the reality," which is that "eating disorders affect people of all ages, [ethnic backgrounds], socioeconomic statuses, and all sizes," Mysko said.

"We also hear from people all the time who say, 'I don't know if I have an eating disorder, because I don't look that sick,' or, 'I'm not that bad,' when in fact they're really, really struggling, and their behaviors are completing disrupting their lives and making it difficult for them to feel good about themselves, engage in relationships, and their health is compromised," Mysko added.

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Overweight and obese youths who experience rapid weight loss are particularly vulnerable to developing eating disorders, a 2013 paper in the journal Pediatrics found.

But medical officials are less likely to recognize and treat their symptoms.

"These case studies really represent a phenomenon we’re seeing in our clinic more and more," Leslie Sim, an author of the study and eating disorders expert for the Mayo Clinic Children’s Center, told The Huffington Post at the time. "Thirty-five percent of kids who are coming in with anorexia nervosa — with restricted eating and significant weight loss — started out in the 'obese' or 'overweight' weight range. And it takes them about a year longer to be identified."

Writer Amy McCarthy suffered from an eating disorder when she was overweight, but when she began losing weight rapidly, nobody seemed to wonder what she was doing to slim down, she wrote in Bustle.

"I learned quickly that doctors didn't give a shit how I was losing weight, so long as I was," McCarthy wrote. "When I visited the campus health clinic for flu shots or birth control, the doctor always gushed about my weight loss. She never asked me how I was losing weight, if I was exercising, or getting enough vitamins. She never asked if I was taking pills that basically amounted to legal speed."

Getting help for eating disorders.

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Early intervention is important for treating eating disorders, Mysko told ATTN:. NEDA has many helpful resources for this.

"If you or someone you care about is struggling with an eating disorder, or you're concerned, don't hesitate to reach out," Mysko said. "Early intervention is really, really critical with eating disorders. We hear from a lot of people who are in recovery who say, 'I really wish I had taken this stress or anxiety about food more seriously at an earlier point.' Because as the behavior and the thoughts progress and become more and more entrenched, it just becomes harder and harder to treat. If you're starting to feel your behaviors around food and weight are becoming a problem, that's enough of a sign to reach out for help."

If you are suffering from an eating disorder, you can call the NEDA confidential helpline at (800) 931-2237.