How common is muscle dysmorphia, the fear that your muscles look too small?

Short answer

By diagnostic criteria, 1 to 3 in 100 people. In gym surveys, 1 in 3 to half crossed the screening line, but that was not a diagnosis. Competitors scored higher, and those with the worst symptoms were 3.3 times as likely to start steroids.

How common is muscle dysmorphia, the fear that your muscles look too small?
'Train more → look smaller to yourself' — does this hold?
Muscle dysmorphia is when your body always looks too small in the mirror and you get anxious if you miss a workout or break your diet. We checked with numbers how common it is and whether it is more common in people who train.
By diagnostic criteria: 1 to 3 in 100
8% of 1,488 men
When 1,488 men in Canada and the US were checked against diagnostic criteria, 41 (2.8%) met them. Among 850 Spanish university men, including follow-up interviews, it was 1.3%. In a survey of 3,618 people in Australia, it was 2.2% of males and 1.4% of females, so women had it too.
Gym surveys gave bigger numbers
1 in 3, up to half, crossed the screening line
Of 141 people lifting weights at gyms in Spain, 31.9% came out at high risk of symptoms. Of 303 gym-goers in Saudi Arabia, 49.8% crossed the screening cutoff. The researchers themselves stated these were questionnaire scores, not diagnoses.
Training does not mean having it
Diagnosed lifters and ordinary lifters were different
In interviews with 54 men recruited from gyms, the 24 with muscle dysmorphia had more body dissatisfaction, depression, anxiety and steroid use. The 30 ordinary lifters showed almost no problems and looked like a regular comparison group of university men. Wanting muscle and having the disorder were different things.
Competing came with higher scores
Competing bodybuilders > bodybuilders > regular lifters
In an analysis that pooled 31 studies with 5,880 people, bodybuilders scored higher on symptoms than regular lifters, and competing bodybuilders scored higher than non-competing ones. Worse symptoms went with more anxiety, depression and perfectionism, and lower self-esteem.
The link to drugs
Those with the worst symptoms: 3.3 times the steroid risk
Of 233 long-time lifters, 102 (44%) had used steroids. The 1/3 with the highest muscle dysmorphia scores when young were 3.3 times as likely to start steroids as the lowest 1/3. In a Spanish survey of 734 people, about 50% of those with muscle dysmorphia used steroids.
Bottom line: rare, but denser in the gym world
The line is crossed when muscle worries upend daily life
By diagnostic criteria it is 1 to 3 in 100, but in gym surveys 1 in 3 to half crossed the screening line. Competitors scored higher, and the most severe group had 3.3 times the steroid risk. The diagnostic criteria were met when worry about muscle caused serious distress or got in the way of daily life.