From BMJ 12th January 2019
Chang AR et al The CKD Prognosis Consortium BMJ 2019;364:k5301
Between 1970 and 2017 a huge number of people were assessed for fatness using body mass index, waist circumference and waist to height ratio. The outcome was that the fatter you get, the more your kidney function declines. This was true whether you started off with normal or impaired kidney function.
The lowest kidney disease was seen in those with a BMI of 20 and this barely changed till a BMI of 25 was reached. After this was a linear progression. By the time your BMI is 40, you have double the risk of kidney function impairment.
The results were adjusted for age, sex, race and current smoking.
My comment: This is a new risk factor for obesity as far as I know.