Yes, surprising even some PhD's think "of course, fat makes you fat."

As regards rodents; the smaller the animal the higher its MBR.

That being said, "knocking out a gene" is rather trivial now using Cas9, there are even DIY experiment kits for sale on Amazon. Tags are available now for $45. Target Gene editing in an adult human is still difficult and experimental, requiring a modified vector such as an adenovirus. It's not FDA approved yet in the US, even though a few people are doing it.