Fig. 3.

Relationships between water turnover (WT) against (A) fat-free mass (FFM), (B) percent body fat, (C) total energy expenditure (TEE), (D) physical activity level (PAL), (E) air temperature, and (F) effective latitude in 1657 females (upper panels; red) and 1013 males (lower panels; blue) aged 20 to 60 years. The blue line represents generalized additive models with integrated smoothness (GAM). Pearson correlation analysis shows positive correlations between water turnover and fat-free mass (r = 0.442, P < 0.001), TEE (r = 0.488, P < 0.001), PAL (r = 0.388, P < 0.001), and altitude (r = 0.100, P < 0.001). Water turnover was negatively correlated with percent body fat (−0.311, P < 0.001). Outdoor air temperature was only weakly correlated with water turnover in the whole sample (r = 0.160, P < 0.001). A significant curvilinear relationship between water turnover and the air temperature and a significant curvilinear relationship between water turnover and effective latitude was observed (see text for details). Average water turnover reached the highest values at around 0° and the lowest at around −50° or +50° of effective latitude. People who lived near the Arctic Circle had higher average water turnover than those who lived around −50° or +50° of effective latitude.