Association of Ambient Indoor Temperature with Body Mass Index in England

Objective: Raised ambient temperatures may result in a negative energy balance characterized by decreased food intake and raised energy expenditure. This study tested whether indoor temperatures above the thermoneutral zone for clothed humans (similar to 23 degrees C) were associated with a reduced body mass index (BMI). Methods: Participants were 100,152 adults (>= 16 years) drawn from 13 consecutive annual waves of the nationally representative Health Survey for England (1995-2007). Results: BMI levels of those residing in air temperatures above 23 degrees C were lower than those living in an ambient temperature of under 19 degrees C (b = -0.233, SE = 0.053, P < 0.001), in analyses that adjusted for participant age, gender, social class, health and the month/year of assessment. Robustness tests showed that high indoor temperatures were associated with reduced BMI levels in winter and non- winter months and early (1995-2000) and later (2001-2007) survey waves. Including additional demographic, environmental, and health behavior variables did not diminish the link between high indoor temperatures and reduced BMI. Conclusions: Elevated ambient indoor temperatures are associated with low BMI levels. Further research is needed to establish the potential causal nature of this relationship.