"减肥温泉疗养地" can be translated as "Weight-loss Hot Spring Resort" or "Slimming Hot Spring Spa Retreat".
"Weight-loss" directly conveys the idea of losing weight.
"Slimming" also implies the process of becoming thinner or reducing body weight.
"Hot Spring Resort" or "Hot Spring Spa Retreat" accurately describes a place where people can enjoy hot spring baths and spa treatments for relaxation and health benefits.
Both translations are suitable, and the choice between them may depend on the specific context or desired emphasis.