To examine the association of 24 h urinary Na excretion and Na:K with obesity in Chinese adults.

Population-based cross-sectional study using a four-stage stratified sampling strategy.

Shandong Province, China.

Chinese adults (n 1906) aged 18–69 years who provided complete 24 h urine samples.

Odds of obesity increased significantly across increasing quartiles of urinary Na excretion (1·00, 1·54, 1·69 and 2·52, respectively, for overweight; 1·00, 1·20, 1·50, and 2·03, respectively, for obesity; 1·00, 1·44, 1·85 and 2·53, respectively, for abdominal obesity (assessed by waist circumference); and 1·00, 1·28, 1·44 and 1·75, respectively, for abdominal obesity (assessed by waist-to-height ratio); P for linear trend <0·001 for all). In addition, odds of abdominal obesity, but not odds of overweight and obesity, increased significantly with successive Na:K quartiles. Additionally, for each increment in urinary Na excretion of 100 mmol, odds of overweight, obesity, abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 46 %, 39 %, 55 % and 33 %, respectively. Similarly, with a 1 sd increase in Na:K, odds of abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 12 % and 15 %, respectively.

These findings suggest that 24 h urinary Na excretion and Na:K might be important risk factors for obesity in Chinese adults.