The opposite of a hypochondriac is someone who is considered a somatophile. A somatophile is a person who typically has a strong appreciation for their own health and body, often displaying a positive attitude toward wellness and an active lifestyle.
Whereas hypochondriacs are excessively worried about having a serious illness and often misinterpret normal bodily sensations as symptoms of disease, somatophiles tend to be more in tune with their bodies in a healthy way. They focus on maintaining their well-being and may actively pursue health-conscious behaviors. In essence, while hypochondriacs dwell on potential illnesses, somatophiles celebrate the vitality of their physical existence.