Yes, it’s true. I was a “model without clothes” for the Art Department at Northern Arizona University, back in the day. I needed the money and they needed a male model. Turns out that they had plenty of females willing to do nude modeling, but finding males willing to bare all were hard to come by. (Wow, was that last sentence full of puns or what? )
You may think that modeling for artists would be easy, but in fact it is quite difficult. If you want to get a feeling for what it’s like, then go lay down in a comfortable position on your couch. Now don’t move for 45 minutes. After just a few minutes you’ll want to shift positions a little. Maybe you put too much weight on your left butt-cheek or something. Before long you’ll find a leg or arm going numb. A pain in your neck starting to crop up. And if you’re nude then you’ll start to feel cold.
Here’s a PG-13 sample of what some of the students drew: