For a considerable number of people, they are not very clear about what constitutes an unhealthy lifestyle, how it affects human health, and what diseases it can cause, etc. It is urgent to popularize knowledge in these aspects. Behaviors that belong to an unhealthy lifestyle include: smoking, excessive drinking, dietary habits such as high fat, high cholesterol, low fiber and high salt, lack of physical activity, mental stress and depression, improper upbringing and education of children, as well as frequent sexual life and excessive nightlife. Smoking is harmful and can cause various cancers such as lung cancer, laryngeal cancer and lip cancer. It also poses risk factors for hypertension, coronary heart disease and cerebrovascular disease, and is an accomplice to pharyngitis and chronic bronchitis. Medical experts believe that if all smokers around the world quit smoking and pay attention to improving their nutrition, the number of cancer patients could be reduced by one third within five years. The occurrence of cardia cancer and gastric cancer is related to long-term excessive alcohol consumption. Excessive drinking and heavy drinking are related to the induction of hypertension, coronary heart disease and cerebrovascular disease. Even when drinking alcohol in moderation, one should be cautious not to consume highly strong spirits. A diet high in fat and cholesterol can cause atherosclerosis due to lipid deposition on the inner walls of arteries. A high-salt diet may cause high blood pressure. A low-fiber diet may induce colorectal cancer. When the protein and fat content in food is high and the intake of crude fiber is low, the food stays in the large intestine for a longer time, and the amount of toxic and carcinogenic substances increases, which is prone to cause cancer. Long-term mental stress and depression may lead to peptic ulcers, high blood pressure and aggravate asthma. According to relevant survey data in our country, among children aged 3 to 6, 30% have high blood lipid levels. The proportion of obese children is increasing year by year. The content of vitamin C in the blood of most children is low, and a considerable number of children are deficient in iron and zinc. This is true even for children with better living conditions and good nutritional status. To be healthy, one has to start from all aspects of daily life and correct bad lifestyles. First of all, one should quit smoking and drinking, keep a regular schedule, avoid overeating, and get rid of unhygienic eating habits. The diet should be balanced with both meat and vegetables, and the intake of nutrients should be balanced. Children's diet should also be controlled. Eating too much can easily lead to obesity. Middle-aged and elderly people should eat more fish, especially sea fish, which is quite beneficial for preventing hypertension, coronary heart disease and cerebrovascular diseases. Eating less grilled, smoked, fried, pickled and fermented foods in daily life can prevent the occurrence of colorectal cancer. You should also eat less sausages, salted fish and pickles. Eat more fresh vegetables and fruits, take good care of yourself and participate in some sports activities appropriately, etc.