Influence of indoor cooling on heat balance and body weight gain in Americans over recent decades

Abstract 1. We address the extent to which the average body mass gains experienced by Americans over the last 40 years may have been due to adaptive thermogenesis by calculating the weight gains which would have been required to maintain heat balance due to environmental changes over this time period. 2. Population-weighted degree-cooling-day data and air-condition adoption rates from 1960 to 2002 indicate that the average American in 2002 was living in an environment, that was, on average, 1.4 °C cooler than in 1960. 3. Under these conditions, heat balance would require body mass gains of approximately 11.7 kg in men, and 9.0 kg in women if adaptive thermogenesis were the sole adaptive strategy utilized. 4. Consistency of the model predictions with actual weight gains leads to the suggestion that body mass may primarily reflect an involuntary adaptive response; correspondingly, extensive exposures to indoor cooling may significantly influence obesity prevalence.