[Objective]

Beside of the obvious like clothes etc.:

Don't drink hot shit like tea etc. if you're outside. The body will look upon it as a heat source and lower your body temperature.

Use two-three t-shirts instead of just one. It'll work as sealing making it more resistant against cold wind and it'll take more of the cold shit to get through the layers and reach your body. Don't pack your clothes too tight as it'll let the cold through more easily.

Also, try not to sweat too much, that shit will cool you down. This might be a challenge if you're fat as fuck.

Wool > mostly anything else.

Jerk off, it gets your heart pumping circulating more of that hot blood through your body. Do it furiously for extra effect.