Obesity Facts

A common cause of death worldwide, obesity is now one of the most serious international public health problems in the 21st century. In 2013, the American Medical Association classified obesity as a medical disease, shining the spotlight on the necessity of preventing and treating this devastating illness.

Causes of Obesity

There are many pathways to obesity, one of which is overeating or bingeing coupled with minimal or no exercise. Often, a person affected by binge eating disorder will consume several thousand calories (or tens of thousands of calories) in one sitting, which far exceeds the daily calories needed to maintain a healthy body weight. Over time, these eating episodes can result in unwanted weight gain, making a person overweight, obese, or morbidly obese. (It is important to note, however, that not all people affected by emotional eating and binge eating are obese, and not all obese people are emotional or binge eaters).

Obesity and weight gain can also be caused by genetic and/or medical conditions, such as hypothyroidism, insulin resistance, diabetes, polycystic ovarian syndrome (PCOS), low testosterone, and Cushing’s syndrome. Additionally, certain medications can cause weight gain, including steroids, some antidepressants, high blood pressure medication, and seizure medication. It is important to have a thorough medical exam to rule out any physical conditions that may be affecting your weight.


Mental and Physical Health Risks

Obesity can lead to a wide variety of mental and physical health risks.

Emotional and Psychological Health RisksMan in Yellow Shirt - Running

  • Depression
  • Anxiety
  • Suicidal thoughts
  • Body dysmorphia
  • Substance use, addiction
  • Loneliness, isolation
  • Low self-esteem
  • Social stigma, stereotyping, bullying
  • Passed up for job promotion or new job

Physical and Medical Health Risks

  • Insomnia, sleep apnea
  • Type 2 diabetes, insulin resistance
  • Gallbladder disease
  • High cholesterol
  • High blood pressure
  • Cardiovascular disease
  • Cancer
  • Osteoarthritis
  • Joint and muscle pain
  • Gastrointestinal problems
  • Reduced life expectancy


Signs and Symptoms of Obesity

Becoming overweight or obese is often a gradual process, occurring in small increments that may make it difficult to notice. The following signs may indicate an unhealthy, excessive body weight:

  • Consistent weight gain
  • Clothes feeling too small and tight
  • Easily winded after walking, going up stairs, or carrying something
  • Feeling tired and lethargic throughout the day, even after sleeping or drinking caffeine
  • Feeling achy throughout your body, especially in your joints and muscles
  • Not fitting in to spaces you used to be able to fit into, such as armchairs, restaurant booths, and airplane seats


Severity Levels and BMI

Currently, the terms ‘overweight’ and ‘obese’ are defined by the medical community using body mass index (BMI) and waist:hip ratio of fat distribution.

BMI is a widely used tool to measure body shape and physical health based on a person’s weight and height. Calculate your BMI now.

According to the World Health Organization, there are six classifications of health based on a person’s BMI:


BMI (kg/m2)


< 18.5


18.5 – 24. 9

Normal weight

25.0 – 29.9


30.0 – 34.9

Class I obesity

35.0 – 39.9

Class II obesity

≥ 40.0

Class III obesity


“Severe obesity” is often defined as a BMI ≥ 35.0, which is equivalent to Class II or III obesity.

“Morbid obesity” is often defined as either: (1) a BMI ≥ 35.0 and obesity-related health issues; or (2) a BMI ≥ 40.0-44.9.

“Super obesity” is often defined as a BMI ≥ 45.

It is important to note that BMI is not used with children and adolescents because their bodies are still growing and so there is no absolute weight they should maintain. Thus, childhood obesity is defined by a weight that is greater than the 95th percentile for their age, gender, and height.