The main symptom of anorexia is

Physical signs and symptoms of anorexia may include: Extreme weight loss or not making expected developmental weight gains. Thin appearance. Abnormal blood counts

Signs
In those with more severe anorexia, body organs can be affected and trigger other symptoms, including:
Fatigue, sluggishness and lethargy.
Cavity formation from vomiting.
Dry and yellowish skin.
Dizziness.
Thinning of bones.
Growth of fine, soft hair covering the body.
Brittle hair and nails.
Muscle loss and muscle weakness.

You would modify how often you work out in reps and sets and also modify calorie intake