This paper has been around for a while, but I hadn't heard about it.

It turns out that Drs Phinney and Wortman, together with a third researcher, looked at the fatty acid profile of oolichan grease the fat that was used by traditional societies on the Canadian Pacific coast and that's got by leaving small fish in a vat to ferment then adding a little water and heating gently for a long time to extract the oil.

Oolichan grease: a unique marine lipid and dietary st... [Lipids. 2009] - PubMed - NCBI

It turns out that the fatty acid profile is pretty much the same as for human adipose tissue. Steve Phinney apparently suggested that that would make it an ideal fuel source for humans. Interesting thought, whether it turns out to be valid or not.

Dr. Wortman says:

Dr Phinney concocted a faux oolichan grease for his own use. He mixes one part butter, two parts olive oil and one part canola oil to approximate the fatty acid profile of the real oolichan grease. He stores this in his fridge and uses it for all his cooking needs.
Which is the preferred fuel: sugar or fat? | Dr. Jay's Blog

I'd steer clear of canola oil which AFAIK is a brand-name for rapeseed oil, which has some issues around it and I think I'd rather put some butter on this and some olive oil on that, depending on the food, rather than mix them. Still, it's an interesting story.