Thicker left back than right back is usually caused by thoracic scoliosis, lipoma or poor posture, you can go to the hospital in time to identify the cause of the disease and targeted treatment. 1. Thoracic scoliosis: one or several vertebral segments of the spine are bent to the side, accompanied by rotation, which causes the left back to be thicker than the right. The incidence of this condition is very high and the age of the patient is also increasing at a young age. 2. Lipoma: The formation of localized excessive fat deposition on the left side of the back, which can also cause the left side of the back to be thicker than the right side of the back, can be examined by ultrasound to see if the diagnosis is confirmed. If so, surgery should be considered to remove the tumor to prevent deterioration. 3. Poor posture: Long-term poor posture can also cause the left back to be thicker than the right. So in normal life, work or sleep, whether standing or sitting. Be sure to keep the thoracic spine often in the natural physiological back arch of the upright position, upright body and in a relaxed state, to avoid a high and low. So in your daily life, you can do some rehabilitation type of exercise with the help of your doctor to avoid excessive use of one side of the arm to work.