The increased protein intake is probably not responsible for much of the heat you are experiencing. However, it is entirely plausible that your metabolism has increased in order to cope with an increased energy intake, and the browning of adipose tissue (metabolic “uncoupling”) is part of that response.
Be careful not to overdo the protein. I believe it was @richard who calculated that ammonia toxicity starts to become a concern around 3.0 g/kg of lean mass, as the uric acid cycle gets overwhelmed. One gram per pound of total body weight is equivalent to over 2.2 g/kg of lean mass, the overage depending on your percentage of body fat.