The historian said the nude photos had been taken to document the development of the child’s malnourishment in case of problems with social services, as she had been underweight when he and his wife adopted her.

Maybe they do things differently in Russia but in California this sort of thing would be verified by regularly scheduled doctor’s checkups (children in the system get MediCal, so it’s free to the parent). Even if they didn’t you could just log the child’s weight on a normal scale to show that they’re on track for their height and age.