Why isn't my tortoise eating a lot?

In their natural environment, a tortoise would hibernate for the winter. My brother's tortoise has already buried himself under the ground to wait out the winter and will emerge around April next year.

If we keep animals in an unnatural environment that interferes with their natural cycles, it is quite possible this would affect their behaviour.

It seems like a good idea to take it to a vet just to make sure it is OK and to get proper guidance on how to provide a suitable environment for your tortoise. Maybe you are doing everything right already but some reassurance wouldn't hurt.

if he's cold his appetite will wan

tortoise stomachs arent very big so they may not need to eat often

It is probably inhaling a lot of second hand smoke.

Not knowing what environment he is currently living in is a hindrance in giving advice.

Basically, if the environment is as I suspect, I suggest increasing the temperature and increasing the length of the day night cycle. A minimum of 12 hours day cycle, a day temperature of 75 - 80F. The only way to know what the temperature is where he is living (the floor of his enclosure) is to check it with a thermometer.

He probably is getting ready to hibernate