[PuppyTailWags]

The article explicitly compares overweight, grade 1 obesity, grade 2 & 3 obesity together, obesity generally, relative to normal weight.

> Random-effects summary all-cause mortality HRs for overweight (BMI of 25–<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30–<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5–<25).

[stnmtn]

Great point, I completely misread that. Edited my original comment!

[PuppyTailWags]

Yeah I had to read this a few times too! I was totally baffled by having 3 categories for obesity, but one of the categories is grade 2 & 3 categories together, and one of the categories is grade 1, 2, & 3 together.