This seems to be the practical issue: if more precise tests like hydrodensitometry were needed before prescriptions were issued, fewer drugs would be sold:
> "That’s especially concerning with the exploding demand for new anti-obesity medications. In the United States, a person can be prescribed semaglutide for weight loss simply if their BMI is 30 (the lower bound of the obesity category) or more. With a BMI of between 25 and 30 — the overweight category — a person needs just one weight-related condition, such as high blood pressure, to get a prescription. “If you have 15 minutes in a visit,” Stanford says, “you’re going to follow the BMI … instead of really taking the time to see ‘Do they need the medication?’”
For a list of more accurate measurement approaches:
> "That’s especially concerning with the exploding demand for new anti-obesity medications. In the United States, a person can be prescribed semaglutide for weight loss simply if their BMI is 30 (the lower bound of the obesity category) or more. With a BMI of between 25 and 30 — the overweight category — a person needs just one weight-related condition, such as high blood pressure, to get a prescription. “If you have 15 minutes in a visit,” Stanford says, “you’re going to follow the BMI … instead of really taking the time to see ‘Do they need the medication?’”
For a list of more accurate measurement approaches:
https://www.medicalnewstoday.com/articles/326331