JAMA: "Relative to normal weight, obesity (grade 2 and 3) was associated with significantly higher all-cause mortality. Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality." User Kelsig, in the Reddit Science subreddit, 05 Jan 2016
Study by CDC: "Relative to normal weight...overweight [25-<30 BMI] was associated with significantly lower all-cause mortality." User jimjamj, in the Reddit Science subreddit, 02 Feb 2013
JAMA: Meta-analysis shows reduced mortality risk for "overweight" individuals (defined as BMI 25 - 30) compared to "normal weight" individuals (BMI 18.5 - 25). User MedStudentNotStudyin, in the Reddit Science subreddit, 04 Jan 2013