Effects of Indoor Thermal Environment on Human Food Intake, Productivity, and Comfort: Pilot, Randomized, Crossover Trial.

OBJECTIVE: It was hypothesized that exposure to mild temperatures above the human thermoneutral zone would decrease caloric intake in a sedentary office environment.

METHODS: Women (n = 25) were randomized in a crossover design to perform seated office work for 7 hours in a thermoneutral condition (control, 19°C-20°C) and a condition above the thermoneutral zone (warm, 26°C-27°C). Food intake was estimated by weight and bomb calorimetry, peripheral temperature by thermal imaging, and thermal comfort and productivity by questionnaires. Mixed effects models were used to examine the effects of thermal condition on caloric intake.

RESULTS: Participants ate, on average, 357 kcal less in the warm condition, adjusting for BMI and peripheral temperature (P = 0.0219). According to the survey results at midday (after 3.5 hours of exposure), 96% of the participants in the warm condition reported being comfortable (n = 24) compared with 32% in the control condition (n = 8). More participants reported being as productive or more productive than usual in the warm condition (n = 22, 88%) than in the control condition (n = 12, 48%).

CONCLUSIONS: This line of research is worthy of further exploration. Untightening climate control toward warmer conditions during summer to increase comfort and productivity while decreasing caloric intake may prove both effective and comfortable.