There are a variety of factors that play a role in obesity — behavior, environment, and genetics may have an effect in causing people to be overweight and obese. 

Environment 

People may make decisions based on their environment or community. For example, a person may choose not to walk to the store or to work because of a lack of sidewalks. Communities, homes, and workplaces can all influence people’s health decisions.

Because of this influence, it is important to create environments in these locations that make it easier to engage in physical activity and to eat a healthy diet. There may be places in your area that support physical activities from parks, trails, and sidewalks to recreation and fitness centers. Even malls provide opportunities for fitness walking.

Understanding environmental opportunities and barriers that we face in our pursuit of a healthy lifestyle may provide some of the knowledge necessary to promote healthy living. This information may also provide ideas for advocacy and civic participation. 

Genetics 

Science shows that genetics plays a role in obesity. Genes can directly cause obesity in specific disorders such as Bardet-Biedl syndrome and Prader-Willi syndrome. 

However, genes do not always predict future health. Genes and behavior may both be needed for a person to be overweight. In some cases, multiple different genes may increase one’s susceptibility for obesity and require outside factors, such as abundant food supply or little physical activity. 

Diseases and drugs 

Some illnesses may lead to obesity or weight gain. These may include Cushing’s disease and polycystic ovary syndrome. Drugs such as steroids and some antidepressants may also cause weight gain. 

A doctor is the best source to tell you whether illnesses, medications or psychological factors are contributing to weight gain or making weight loss hard.

Source: Centers for Disease Control and Prevention