According to a study in the Archives of Internal Medicine, an unhealthy lifestyle is defined as a lifestyle where a person engages in activities that are known to be detrimental to one's health, such as smoking, not exercising regularly or enough, eating unhealthy foods on a regular basis, and not maintaining a healthy weight. An unhealthy lifestyle can vary by degrees, and some may determine that being slightly unhealthy is acceptable for the sake of quality of life.
Smoking is an activity that directly lowers the health of a human's respiratory system and related systems. According to the Centers for Disease Control and Prevention, smoking damages almost every organ in the body and increases the chance of developing lung cancer and heart disease. Smoking may or may not be part of an unhealthy lifestyle, but it is never part of a healthy lifestyle.
Exercise is important for cardiovascular health, overall health and weight maintenance. Regular strenuous exercise burns calories and stimulates muscle tissue, which leads to a better muscular composition and a lower overall weight. Being overweight puts excess stress on joints and bones, as well as increases your risk for diabetes and heart disease, according to the National Health Service.
The food that a person eats, both in terms of quantity and quality will affect body weight and composition. Healthy foods like fruits and vegetables contain vitamins and minerals the body needs.