Hot and humid weather in Malaysia seems to discourage obese individuals from exercise in the outdoor. The purpose of this study was to examine the effect of fluid balance on thermoregulatory responses in obese individuals during exercise in hot condition. A total of 10 obese (23.0 ± 5.2 years; 92.2 ± 9.2 kg; BMI: 32± 2.5 m²/kg; 32.4 ± 2.6% BF) and 10 normal weight individuals (21.0 ± 1.8 years; 65.6 ± 4.2 kg; BMI: 23.0 ± 1.2 m²/kg; 11.1 ± 1.1% BF) were recruited for this study. Subjects underwent 50 min of cycling at 50% VO_2max under 4 conditions: (i) euhydrated in thermoneutral condition (24.5°C; 53.8 rh) (EUT), (ii) hypohydrated in thermoneutral condition (HYT), (iii) euhydrated in hot condition (34.7°C; 54% rh) (EUH) and (iv) hypohydrated in hot condition (HYH). Subjects were instructed not to ingest fluid for 8 hours prior to the hypohydrated condition trials. No significance difference was found between obese and normal weight groups in heart rate (HR), VO², core temperature (T_core), skin temperature (T_sk) in all the 4 trials. Sweat loss in the normal weight group was greater than the obese group (1.21% vs. 0.75% ΔBW; 1.70% vs. 0.99% ΔBW) in EUT and EUH trials (p=0.035; p=0.017, respectively). HR in EUH trials were significantly higher than EUT trials at 10 min in the normal weight group and at 20 min of exercise in the obese group (p<0.05). HR in HYH trials were significantly higher than HYT trials at 0 min in the normal weight group and at 10 min the in obese group (p<0.05). With ~ 1% of BW loss prior to exercise, obese individuals have similar physiological responses as normal weight individuals when exercising in the heat (35°C; 64% rh) for 50min at 50% VO_2max of cycling.