The association between weight-waist-adjustment index and serum folate in US adults: NHANES 2013 to 2018.

Obesity is closely related to human metabolism and a variety of diseases. The association between weight-waist-adjustment index (WWI, a new index for obesity) and serum folate has not been sufficiently explored. Data from the National Health and Nutrition Examination Survey (2013-2018) was used to explore the correlation between WWI and serum folate. 12,757 adult participants were included in our study. In order to discern the relationship, we conducted weighted multiple linear regression analysis, generalized weighted smooth curve fitting and threshold effect analyses. Additionally, we executed subgroup analysis and interaction tests. There was a negative correlation between WWI and serum folate. In subgroup analysis, the relationship between WWI and serum folate were more pronounced among females, the elderly (65-80 years), nonsmokers, and those with hypertension or stroke. Furthermore, a nonlinear association between WWI and serum folate was found using smooth curve fitting (likelihood ratio = 0.014), with a threshold identified at WWI of 7.42. We discovered a stronger association between WWI and serum folate than other obesity markers including body mass index and waist circumference. Our study could help obese people predict serum folate and manage their nutrition well.