When the body resistance is strong, evils (including bacteria, viruses, etc.) will not easily invade the human body, allowing it to remain healthy and disease-free. Obese people have lower immune function which provides an internal environment for the invasion of pathogenic microorganisms. Obese people are prone to heat intolerance, sweating, lower extremity edema, varicose veins and other symptoms. People’s epidermis becomes easy to break, and once there is trauma or upper respiratory tract infection, the pathogenic microorganisms easily grow and reproduce in the affected area. The adipose tissue is a very good medium for bacteria which creates the conditions for breeding. Research shows that the iron and zinc content of obese people’s serum is lower than normal. The iron is related to immune activity and the zinc deficiency can affect cell immune function. Lack of iron and zinc will reduce lymphocytes and macrophages function and reduce disinfection capacity. The most common infections in obese people are upper respiratory tract infections, skin infections, urinary tract infections and genital infections.