Hannah, an eight-year-old girl in Los Angeles, has always had a difficult relationship with food.

Her mother Michelle recalls how, even at the age of 1, Hannah struggled transitioning from formula to whole milk, refusing to drink the latter. Solid foods weren't any better. Her daughter sometimes attempted to eat them, but often spit them out or put out her hand in protest.

"I again was like, 'OK, well, not everybody likes milk,' " says Michelle, who withholds her family's last name for her daughter's privacy. "But as she got older, I saw that it was still happening."

It wasn't until much later that Michelle learned Hannah has avoidant restrictive food intake disorder, or ARFID. A relatively new entry in the Diagnostic and Statistical Manual of Mental Disorders, ARFID is classified as an eating disorder; however, unlike other eating disorders, like anorexia or bulimia, ARFID doesn't have to do with one's body image. Rather, it stems from severe anxiety and fear surrounding food.

Many with ARFID get characterized as picky eaters, when, in reality, their food issues go much deeper. In Hannah's case, ARFID almost led her to being put on a feeding tube.

What's turned things around, Michelle says, has been Hannah's Instagram account, managed by her mother, where thousands of commenters cheer Hannah on as she pushes herself to try new foods and educates her 1.5 million followers on the oft misunderstood condition.

"It's been incredible," Michelle says. "She is motivated. She is encouraged. She knows what an impact she's making on so many people, and she knows that she's overcoming her own struggles and her own challenges."

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What is ARFID?

ARFID is an eating disorder that can cause weight loss, stalled growth, significant nutritional deficiencies and interference in relationships, school or work, according to the National Eating Disorders Association, or NEDA.

"Children who don’t outgrow normal picky eating, or in whom picky eating is severe, appear to be more likely to develop ARFID," NEDA's website reads. It adds: "Although many children go through phases of picky or selective eating, a person with ARFID has a diet that is so limited it leads to medical, nutritional, and/or psychosocial problems."

Though research on ARFID is limited, NEDA notes studies have found between 0.5-5% of people have it. Additionally, conditions such as autism, ADHD, anxiety and depression are common among those with ARFID.

According to Cleveland Clinic, the exact cause of ARFID remains unknown, but research suggests it may be genetic or a result of anxiety, fear, environmental influence or trauma.

People with ARFID tend to avoid food for one of three reasons: out of fear something bad will happen, like choking or vomiting; out of aversion to certain sensory aspects of food, such as its texture, flavor, smell or color; or out of lack of interest in eating.

Some with ARFID experience one or two of these reasons. Hannah experiences all three.

The consequences of Hannah's ARFID have been severe. She's struggled with migraines, hours-long cycles of vomiting and frequent constipation, her mother says. Her bone development and height growth also severely slowed, despite having a 5'8" mother and a 6'4" father.

It's also impacted her socially. Like others with ARFID, Hannah's fears surrounding food have kept her from going to restaurants or eating with family. It's also made her want to skip birthdays and other events with kids, out of fear they'll pressure her to eat something she doesn't like or make hurtful comments.

"It got to the point where she wouldn't even want to go to my parents' house, to her grandparents' house, and that was very hard for me, because I'm like, 'I don't understand. What is it? They love you.' " Michelle says. "She eventually opened up to us and basically said, 'Every time you guys talk about food, it makes me really anxious.' And that's when I realized, 'OK, this is way more than just her being a picky eater. There's something going on. There's an underlying thing that we need to figure out.' "

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Thousands cheer on Hannah's ARFID journey

Michelle eventually found an out-of-state therapist specializing in ARFID for Hannah. Getting her daughter to eat remained a challenge, but she found that, if she asked Hannah to try a new food on camera so she could send it to her therapist, her daughter obliged.

Eventually, Michelle started posting the videos on Instagram to educate friends and family about what Hannah was going through. She started posting in late January, and, within a few days, one video hit a million views.

Hannah's account has taken off since and now has 1.5 million followers, many of whom are fascinated with the condition and offer encouragement in the comments. Michelle says the account has also helped others realize they too may have ARFID.

"There's so many people out there who can relate to her, whether it's kids themselves or parents who are having struggles with their own kids or even people who have these issues that never knew that it had a name," Michelle says. "It's been amazing for her because she doesn't feel alone, and she realizes that there's so many other people out there like her."

The positive feedback has been key for Hannah in pushing through her fears, Michelle says. Every day, Hannah films herself trying a new food and shares her thought process before and after. Even if she hates it, Hannah always takes least three bites, so she can be sure of her opinion.

Since sharing her journey on Instagram, Hannah has tried 107 new foods. She's liked 41 of them − meaning she's open to eating them again, though doing so may still give her anxiety − and she's found seven new safe foods, which she can eat with no anxiety.

It's an improvement that seemed out-of-reach not long ago. "The amount of food that she's tried since she started doing this, not even three months ago, is more food than she's eaten in her entire life," Michelle says.

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Michelle hopes to launch a nonprofit dedicated to providing low-income people with access to ARFID therapy. In the meantime, she says, Hannah remains determined to keep trying new foods.

"She is realizing through this that if she's eating more, then her energy is much better − and, if her energy is much better, then she can do things that kids do. She loves to dance," Michelle says. "Before, it was really hard for her to even get off the couch, because she was just so weak and lethargic all the time, whereas now, she's going for the gold. She wants to do things. She wants to go places. She wants to see things. She wants to be around people. Her whole attitude changed, and she's so much happier."