I got thinner overall, does it call muscle atrophy?

Atrophy: Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, excessive amount of apoptosis of cells, and disuse or lack of exercise that is needed for muscles and tissue to remain healthy. Getting thin may simply be a loss of fat, and a term to describe decrease girth.

Not really: Atrophy of muscle is usually seen in peripheral nervous systems and is associated with other signs such as fasciculation and diminished reflexes. Best to check with your doctor.