Thick arms may be related to genetics, behavioral habits, lack of exercise and other reasons. 1. Heredity: there is a great relationship between thick arms and genes, if the parents have a similar situation, the children will easily also have thick arms. 2. Behavioral habits: If you often carry heavy objects, your arms will be muscular because of frequent exertion, and the phenomenon of thick arms will occur. 2. Lack of exercise: If the body lacks exercise, it may cause more and more accumulation of fat on the arm, and will also appear arm thick. It is recommended that people with thick arms can take appropriate treatment under the guidance of professionals according to different reasons.