Tuna belly is richer, loin is leaner.

That’s the short answer. Belly (otoro) is marbled with fat, soft, and practically melts on the tongue. Loin (akami) is leaner, firmer, with a cleaner, more direct tuna flavor.

If you’ve ever had a slice of sashimi that felt buttery and luxurious, that was belly. The fat content is significantly higher, so the texture is almost like a cross between fish and wagyu. It’s what people pay extra for.

Loin is what you usually get in a standard tuna poke bowl or a can of chunk light tuna. It’s meatier, holds its shape better, and tastes more like “tuna” — that slightly metallic, ocean-forward flavor. It’s also much cheaper.

So belly is for indulgence, loin is for everyday eating. Neither is better; they’re just completely different experiences.

Don’t confuse belly with the even fattier toro (which is usually the belly of a bluefin). But that’s a whole other rabbit hole.