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What Is Considered Obese?

What Is Obesity?

You are obese if your body mass index (BMI) is 30 or above. The BMI is an imperfect measure, however, so you also should have a physical exam and other tests if you want medical help losing weight.
You are obese if your body mass index (BMI) is 30 or above. The BMI is an imperfect measure, however, so you also should have a physical exam and other tests if you want medical help losing weight.

When a person’s weight is higher than what is appropriate for their height, they are considered overweight or obese. 

A measure called the body mass index (BMI) is used is used to determine if a person is obese.

  • A BMI less than 18.5 is underweight 
  • A BMI 18.5 to under 25 is normal
  • A BMI 25.0 to under 30 is overweight 
  • A BMI 30.0 or higher is obese
    • Obesity may be divided into sub-categories 
    • Class 1: BMI of 30 to less than 35
    • Class 2: BMI of 35 to less than 40
    • Class 3 (extreme or severe obesity): BMI of 40 or higher 

For most people, the BMI roughly correlates with body fat percentage, but it doesn’t account for extremely tall people or heavily muscled people. Body fat percentage, measured or calculated through various means, is the best way for your doctor to get detailed info to help you lose weight.

What Causes Obesity?

Obesity is primarily caused by an unhealthy lifestyle: 

  • Eating too much
  • Consuming unhealthy foods
  • Too little physical activity

Other risk factors for developing obesity include:

  • A mother's habits during and after pregnancy 
    • Woman who eat a high calorie diet, have diabetes, or smoke during pregnancy have a higher chance of having children who become obese as adults
    • Babies who are fed formula may be more likely than breastfed infants to develop obesity 
  • Weight gain and unhealthy habits during childhood
    • Children or teens who are overweight or obese are more likely to become obese adults 
  • Sleeping too little 
  • Taking certain medicines, such as some antidepressants
  • Certain hormonal conditions such as polycystic ovary syndrome (PCOS)

How Is Obesity Diagnosed?

Obesity is diagnosed with a physical examination and a calculation of the patient’s body mass index (BMI). The BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters.

  • A BMI 30.0 or higher is obese.

Obesity may be divided into sub-categories:

  • Class 1: BMI of 30 to less than 35
  • Class 2: BMI of 35 to less than 40
  • Class 3: (extreme or severe obesity): BMI of 40 or higher 

What Is the Treatment for Obesity?

The treatment for obesity is weight loss. Lifestyle changes that can help with weight loss include: 

  • Healthy, balanced diet
    • Low-calorie
    • Low-fat/low-calorie
    • Moderate-fat/low-calorie
    • Low-carbohydrate diets
    • Vegan/whole-food plant-based diet
    • Mediterranean diet
  • Regular exercise
    • The 2008 Federal physical activity guidelines recommend adults get:
    • Aerobic activity
      • 150 minutes of moderate-intensity aerobic activity each week, OR
      • 75 minutes of vigorous-intensity aerobic activity each week, OR
      • An equivalent mix of moderate- and vigorous-intensity aerobic activity
      • Performed at least 10 minutes at a time, preferably spread throughout the week
    • Muscle strengthening 
      • 2 or more days per week
      • Work all major muscle groups: legs, hips, back, abdomen, chest, shoulders, and arms
      • Repeat exercises for each muscle group 8 to 12 times per set group should be and increase the weight or do another set as exercises become easier
  • Behavioral modification
    • Behavior therapy
    • Monitoring food intake, physical activity, and controlling cues and stimuli in the environment that trigger eating

For people unable to lose weight with lifestyle changes, options include:

  • Medications
  • Medical devices
    • Laparoscopic adjustable gastric banding (LAGB) 
    • Electrical stimulation (vagal blockade) systems 
    • Intragastric balloon systems 
    • Gastric emptying (aspiration) systems 
    • Hydrogels 
  • Bariatric surgery (weight loss surgery)  
    • Laparoscopic adjustable gastric band
    • Gastric sleeve surgery (sleeve gastrectomy)
  • Gastric bypass
    • Biliopancreatic diversion with duodenal switch (not commonly used)

What Are Complications of Obesity?

Complications of obesity include: 

What Is the Life Expectancy for Obesity?

People who are obese die younger than people who are a healthy weight, and the heavier a person is, the greater the risk of death. 

People with "central obesity" (extra weight in the belly area, even if the BMI is normal) might also be at risk of dying younger.

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