Abstract
We hypothesized that exposure to temperatures above the thermoneutral zone (TNZ) would decrease food intake in young adults in a sedentary office environment over a 2-h period. Participants wearing standardized clothing were randomized to perform routine office work in the TNZ, considered control (19-20°C), or above the TNZ considered warmer (26-27°C) using a parallel-group design (n = 11 and 9, respectively). Thermal images of the inner canthus of their eye and middle finger nail bed, representing proxies of core and peripheral temperatures, respectively, were taken at baseline, first, and second hour during this lunchtime study. Heat dissipation was estimated using peripheral temperature. General linear models were built to examine the effects of thermal treatment on caloric intake and potential mediation by heat dissipation. Researchers conducted the trial registered as NCT02386891 at Clinicaltrials.gov during April to May 2014. During the 2-h stay in different ambient temperatures, the participants in the control conditions ate 99.5 kcal more than those in the warmer conditions; however, the difference was not statistically significant. Female participants ate about 350 kcal less than the male participants (p = 0.024) in both groups and there was no significant association between caloric intake and participant's body mass index (BMI). After controlling for thermal treatment, gender and BMI, the participant's peripheral temperature was significantly associated with caloric intake (p = 0.002), suggesting a mediating effect. Specifically, for every 1°C increase in peripheral temperature suggesting increased heat dissipation, participants ate 85.9 kcal less food. This pilot study provided preliminary evidence of effects of thermal environment on food intake. It suggests that decreased food intake in the experimental (warmer) environment is potentially mediated through thermoregulatory mechanisms.
Highlights
Previous studies suggest increased time spent outdoors is associated with lower body mass index (BMI) [1, 2]
Research in mice and livestock shows that food intake and subsequently, weight gain is reduced in high-ambient temperatures [6,7,8,9]
Physically active, healthy men, food intake is inversely proportional to temperatures above the thermoneutral zone (TNZ) [10]
Summary
Previous studies suggest increased time spent outdoors is associated with lower body mass index (BMI) [1, 2]. The range of ambient temperatures with which a healthy adult can maintain body temperature without expending energy beyond the normal basal metabolic rate is the thermoneutral zone (TNZ) [4]. There is minimal information on how small changes in ambient temperature affect food intake in the general public. There is limited information on how small changes in ambient temperature exposure above the TNZ affect food intake. Recent research suggests that small changes in diet and physical activity over time could lead to prevention of further weight gain [11]. We hypothesized that exposure to temperatures above the thermoneutral zone (TNZ) would decrease food intake in young adults in a sedentary office environment over a 2-h period
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