An assessment of the occupational heat stress recommendations in adults with obesity

Occupational heat stress and hydration recommendations aim to prevent core temperatures from exceeding 38.0°C and dehydration in unacclimated workers. These guidelines do not consider individual differences in body composition. We hypothesized that core temperatures would be higher in adults with obesity during simulated occupational heat stress compared to adults without obesity when adhering to the current heat stress recommendations. Twenty-two unacclimated adults with [<i>n</i> = 10; 6 women; body fat % (37 ± 5%)] or without [<i>n</i> = 12; 7 women; body fat % (22 ± 6%)] obesity completed a 4-hour (half workday) exposure to a fixed wet-bulb globe temperature (WBGT) and work intensity. Work-rest ratio was 30 minutes of walking and 30 minutes of seated rest each hour. Work intensity [i.e. metabolic heat production (H_prod)] was prescribed as a function of WBGT (27.6 ± 0.5°C) and normalized to body mass (5.0 ± 0.4 W•kg^-1). All subjects were provided 237 mL of Gatorade every 15 min and drank <i>ad libitum</i>. Peak core temperature was higher in the obese (38.4 ± 0.3°C) compared to the non-obese (37.7 ± 0.4°C; <i>p</i> < 0.01) group. Mean core temperature was higher in the obese (37.9 ± 0.2°C) compared to the non-obese (37.4 ± 0.3°C; <i>p</i> < 0.01) group. <i>Ad libitum</i> drinking was not different between the obese (1.8 ± 0.8 L) and non-obese (1.8 ± 0.7 L; <i>p</i> = 0.94) groups. Percent change in body mass did not differ between the obese (-0.6 ± 0.6%) and non-obese (-0.4 ± 0.9%; <i>p</i> = 0.63) groups. Adherence to the heat stress recommendations during a 4-hour exposure resulted in elevated core temperature responses in adults with obesity compared to adults without obesity.