More data: I once lost 80 pounds purely through dieting. I really didn't change my exercise habits at all throughout (vs before I dieted).

I was partially testing this theory, in fact. This was a decade ago, but I was aware of this line of thinking at the time. Specifically, that dieting is more important for losing weight, and exercising is more important for being healthy (losing weight alone really didn't make me noticeably healthier, btw).

I found that, for me, this was entirely true.