ThermiTight is certainly the best nonsurgical treatment to tighten the buttocks and virtually anywhere you have skin. The tightening effect is limited, however. In cases where there is lots of loose skin, the skin will also be tightened, but possibly not as much as you might want. You should consult a PS who does this procedure frequently to get a professional opinion to see if the ThermiTight would meet your goals.
The ThermiTight tightens skin in the neck, arms, legs reducing cellulite, and even elevates saggy breasts, and in the form of The ThermiVA, tightens the vaginal and surrounding areas.
Thank you for your question and best wishes for the holidays.