The Claim

In nonathletic transgender women undergoing feminizing hormone therapy, fat mass increases by approximately 30% and lean mass decreases by about 5% within the first 12 months, with continued declines in muscle area observed over a 3-year period, indicating that hormone therapy is associated with significant shifts in body composition toward a more feminine profile.

Source: The Impact of Gender-Affirming Hormone Therapy on Physical Performance

What the research says

Roughly balanced

Support and challenge are close. The picture may shift as more studies come in.

Supports
1score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Quantitative
1 study reviewed
In plain English

Trans women who aren't athletes and take feminizing hormones tend to gain fat and lose muscle in the first year, with muscle continuing to decrease over three years, leading to a more typically feminine body shape.

See the scientific wording

In nonathletic transgender women undergoing feminizing hormone therapy, fat mass increases by approximately 30% and lean mass decreases by about 5% within the first 12 months, with continued declines in muscle area over 3 years, indicating that hormone therapy is associated with significant shifts in body composition toward a more feminine profile.

What the research says

1 study
  1. Study: The Impact of Gender-Affirming Hormone Therapy on Physical Performance

    The study looks at the same hormone treatment in the same group of people and finds the same changes in fat and muscle that the claim talks about.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

Fit Body Science verdict — we translate health claims into clear verdicts backed by peer-reviewed research.

Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.