Most eating disorders begin during adolescence, with average onset ages falling between 12 and 19 depending on the type. Anorexia nervosa tends to appear earliest, around age 18 to 19 on average, while binge eating disorder can develop much later, often not surfacing until the mid-20s. But these averages mask a wide range: some children show signs before age 10, and others develop eating disorders well into adulthood.
Onset Ages by Type of Eating Disorder
Each eating disorder follows a somewhat different timeline. Anorexia nervosa has the earliest average onset at about 18.9 years, with most cases developing between ages 16 and 22. Bulimia nervosa follows closely with an average onset of 19.7 years, though its range is actually broader on the younger end, stretching from 14 to 22 for the middle 50% of cases. Binge eating disorder starts considerably later, with an average onset of 25.4 years and a wide spread from 17 to 32.
ARFID (avoidant/restrictive food intake disorder) breaks this pattern entirely. It typically starts earlier in life than any other eating disorder, often in childhood, and people with ARFID tend to go longer before receiving treatment compared to those with anorexia. Unlike other eating disorders, ARFID affects boys and men at roughly the same rate as girls and women.
How Young Can Eating Disorders Start?
While the teenage years represent the highest-risk window, eating disorders can appear in children as young as 7 or 8. A large nationally representative U.S. study found that the median onset age for anorexia, bulimia, and binge eating disorder in adolescents ranged from 12.3 to 12.6 years, earlier than what retrospective adult surveys tend to capture. This gap likely reflects the fact that adults looking back on their experiences may not pinpoint when symptoms truly began.
A meta-analysis covering more than 63,000 young people aged 7 to 18 found that about 22% showed signs of disordered eating. That rate climbed with age, meaning older adolescents were more affected than younger children. Still, even among the few studies that focused on children ages 7 to 10, disordered eating was present. In children this young, the signs often look different from what people expect. Rather than expressing fear of gaining weight in adult terms, younger children may skip meals, eat unusually small portions, refuse foods with sugar or fat, make frequent comments about their appearance, or exercise compulsively.
Why Adolescence Is the Highest-Risk Period
Recent data makes the concentration of risk in adolescence especially clear. Among females ages 13 to 18, diagnosed eating disorder rates jumped from 120 per 100,000 in 2017 to 916 per 100,000 in 2022. That’s nearly an eightfold increase in five years. By comparison, rates in the 19 to 26 age group stayed relatively flat at around 328 per 100,000, and rates among children ages 5 to 12, while rising, reached 139 per 100,000 in 2022.
Puberty plays a direct biological role. Rising levels of estrogen and testosterone don’t just change the body’s shape; they act on the developing brain in ways that influence eating behavior and anxiety. Estrogen, for example, directly affects appetite regulation and correlates with levels of disordered eating in women. Because the adolescent brain is still maturing, hormonal exposure during this window can have lasting organizational effects on mood and behavior that persist into adulthood. Research in both humans and animals suggests that the earlier puberty begins relative to brain development, the greater the potential for these permanent changes.
This means early puberty carries particular risk. A young person whose body matures ahead of their peers may face both the biological vulnerability of early hormone exposure and the social stress of looking different from classmates.
Psychological and Social Triggers
Biology sets the stage, but the environment often pulls the trigger. Four factors consistently predict the shift from no symptoms to disordered eating during adolescence: low self-esteem, depressive symptoms, substance use, and the quality of family communication.
Family dynamics matter in specific ways. Adolescents who reported higher levels of family communication and caring had 34% lower odds of moving from no symptoms into disordered eating. On the other hand, being teased about weight by family members was associated with 38% higher odds of developing disordered eating. Peer weight teasing, interestingly, was not a significant predictor in the same analysis, suggesting that what happens at home carries more weight than what happens at school during this critical period.
The combination appears to be especially potent: adolescents who were teased about their weight by family and also experienced depressive symptoms were at particular risk for developing disordered eating as they entered early adulthood.
Differences Between Boys and Girls
The evidence on whether boys develop eating disorders at a different age than girls is genuinely mixed. Some population-level data shows no sex differences in age of presentation, including for early-onset cases under age 14. Other research suggests that boys and men tend to develop eating disorders somewhat later, particularly anorexia.
What does seem clear is that boys’ symptoms intensify over adolescence. Loss-of-control eating may be nearly twice as common in older boys compared to younger boys, and concerns about weight and body shape increase substantially from early to late adolescence. For muscle dysmorphia, a condition where someone becomes preoccupied with not being muscular enough, the average onset falls in later adolescence. A preference for a more muscular build can start much younger, but it typically doesn’t cross into disordered territory until the late teen years.
Eating disorders in boys and men remain underdiagnosed, partly because screening tools were designed around symptoms more common in girls and partly because the cultural assumption that eating disorders are a “female problem” leads families and clinicians to miss the signs.
Late-Onset Eating Disorders
Eating disorders are not exclusively a young person’s problem. Binge eating disorder, with its wide onset range of 17 to 32 for the middle half of cases, regularly appears for the first time in adults who had no symptoms as teenagers. Life transitions that involve stress, loss of identity, or changes in routine, such as divorce, career loss, or menopause, can trigger eating disorders in people with no prior history.
Late-onset cases are often overlooked because neither the person experiencing them nor their doctors are watching for it. An adult who begins restricting food or bingeing in their 30s or 40s may attribute it to stress or “getting healthier” rather than recognizing it as a disorder.
Warning Signs at Any Age
Physical and behavioral red flags overlap across age groups but can be easy to rationalize. Frequent comments about weight or appearance, skipping meals, eating noticeably small portions, calorie tracking, hiding or sneaking food, and avoiding social events that involve eating are all behavioral signs worth paying attention to. Excessive exercise that feels compulsive rather than enjoyable is another common pattern.
Physical signs that point to a more serious problem include rapid weight changes in either direction, fatigue, hair loss, fainting, and feeling cold all the time. In children and teens, a slowing or stalling of expected growth can be an early medical sign. Heart rate changes, blood pressure drops, and electrolyte imbalances are the complications that make eating disorders medically dangerous, but these typically aren’t visible from the outside, which is why behavioral changes are the more practical thing to watch for.