Hep C can cause thyroid problems, more often slowing it down, a condition called hypothyroidism. Although this could cause weight gain, symptoms of hepatitis C, like poor appetite and nausea, usually cause weight loss. Later, when hepatitis C liver damage turns to cirrhosis, it replaces the damage with scar tissue. Scarred liver tissue can’t work as well as healthy liver tissue can. This affects your body’s ability to digest food, and you may lose weight unexpectedly.