It is skewed and makes no sense for them to test it on monkeys but there is no real way to know until tested on humans. Monkey Business, that term has been coined for a reason. If you jump around all over the place being over active and jumping all over things you could easily hear someone calling you a monkey. They are much more active than humans so it should not be comparable in a weight loss/gain study.
Except for the fact that lab monkeys stay in cages, it's not like they're in a zoo habitat or anything. C'mon now.