What Causes Obesity?

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Obesity1 is a complex medical disease, not a lifestyle choice. So what causes obesity? Obesity is caused by the accumulation of fat cells (adiposity), which eventually leads to fat cell dysfunction and results in negative effects on the entire body due to extra fat tissue. Increased fat storage in the body results from energy imbalance due to consuming more calories (energy) than the body uses for functioning (i.e., metabolism or exercise). Additionally, there is a range of contributing factors to developing obesity.

What Causes Obesity?

  • Genetics: Through studying identical twins, we have found that the rate of inheriting a high body mass index (BMI) is between 40% and 70%. There are 300 different genes2 associated with obesity. So far, there are 11 genetic abnormalities that directly cause obesity.
  • Nutrition: Growing evidence shows that not all calories are created equal. Certain foods, such as refined carbohydrates and unhealthy saturated fats, contribute in greater proportion to obesity.
  • Hormones: Abnormalities in several biological pathways are involved in obesity. Insulin resistance, which causes the body not to process sugar properly, has been heavily implicated in obesity.
  • Infection: Adenovirus 36, a cold virus, has been associated with obesity.
  • Medication: Several prescription medications are associated with weight gain.
  • Related Diseases: Medical conditions, such as polycystic ovary syndrome, depression, and Cushing’s syndrome are associated with obesity.
  • Environment: Family, culture, and even where you live can have a significant impact on developing a high BMI.
  • Sleep: Adequate sleep is essential for weight regulation. Disrupted sleep and sleeping for less than 7 hours or more than 9 hours can cause obesity.

Although what causes obesity is multifaceted, there is hope. An obesity medicine specialist can help to develop a comprehensive medical obesity treatment plan. Search the Obesity Medicine Association’s clinician directory to find an obesity medicine specialist in your area.

1Obesity is defined as: BMI greater than 30 kg/m2; waist circumference greater than 35 inches or 88 centimeters in women, or greater than 40 inches or 102 centimeters in men; body fat percentage greater than 40%cm.
2Genes carry DNA, which helps to determine our physical features (National Library of Medicine).


This article was written by Sylvia Gonsahn-Bollie, MD. Dr. Gonsahn-Bollie is an internal medicine physician and obesity medicine physician in Richmond, Virginia.

Photo courtesy of the World Obesity Federation.