accepted by the

ii Obesity in the United States has been continuing increasing and cited as a major health issue in recent decades. Many researchers have studied its socio-economic cause, but very few studies center on the potential influence that health insurance has on obesity. In our common sense, health insurance reduces the money that we pay for health care and makes many treatments’ cost affordable which we may choose to give up originally due to our financial situation. However, everything has two sides. The benefits from insurance also can lead people to change their choices and behaviors. As an insured, people may take on more health risk than they did without insurance. Insurance reduces people’s responsibility, and reduced responsibility decrease health consciousness. Using 3 years of individual-level data from the Integrated Health Interview Series corresponding to year 2000, 2005 and 2010, I attempt to research if the presence of health insurance has effect on body weight. Then by dividing overall BMI into detailed group, I study further on if health insurance affects overweight and obesity. The 2SLS result shows insurance is positively related with BMI, so insured individuals tend to be heavie