When I was 330 lbs. (150kg) it would take me 30 minutes to walk a mile, and I would be post-exercise dumb for at least 30 more. You don't want to the post-exercise dumb for class (taking or teaching).
Now (225 lbs. [~102kg]), it would still take me about 15 minutes to walk it, tho at that pace my HR wouldn't significantly increase, and I might decide to take the bus instead, if there's any sort of weather.
Yeah, I'm still obese. I almost got down to overweight, I was within 3kg, but... I've had/been some setbacks. By height + BMI, I should be targeting 165lbs. / 75kg, but I'm still finding it impossible to stick to a diet that provides a calorie deficit. (I have in the past, but don't seem to now.)
My physical health is better by basically any metric. I encourage anyone that is overweight to lose it.