As you get fitter and healthier your body gets better at losing excess heat through sweating.
Not quite,
excessive heat has got multiple reasons.
Eating much, processing food generates heat.
Cardio not up to date,
better cardio(vascular system), bigger hart, less beats a second, less heat.
Check-out your supplements.
Do you use fat-burners, caffeine-supps, energydrinks etc. Maybe a mix in certain supps.