What is Obesity?
Obesity is a multi-faceted and highly complex medical condition. There is no shortage of information on the topic, but how does one separate fact from fiction? In this section, gain a basic understanding of obesity and learn some key terminology.

Obesity Explained1

  • The terms "overweight" and "obese" describe weight ranges that are above what is medically accepted as healthy
  • Being in either the overweight or obese weight ranges increases the likelihood of certain diseases and health problems
  • Over one-third of U.S. adults (~36%) are obese
  • Approximately 12.5 million children and adolescents aged 2-19 (17%) are obese
  • Obesity affects people of all ethnic backgrounds, income and education levels. The highest overall obesity rates continue to be found amongst racial and ethnic minorities, those with lower levels of education and lower income levels, and in rural populations

As an Adult, How Do I Know If I Am Overweight or Obese?

  • Weight and height are used to calculate a number called the "body mass index" (BMI). For most people, BMI is a good estimate of body fatness.
  • A BMI of 25 to 29.9 is considered overweight.
  • A BMI of 30 or higher is considered obese.
  • To find your BMI, try one of these BMI calculators:

For example, if your height is 5' 9" and you weigh between 169-202 lbs., you are considered overweight; if you weigh over 202 pounds, you are considered obese.

Height Weight Range BMI Considered
5' 9" 124 lbs. or less Below 18.5 Underweight
125 lbs. to 168 lbs. 18.5 to 24.9 Healthy weight
169 lbs. to 202 lbs. 25.0 to 29.9 Overweight
203 lbs. or more 30 or higher Obese

How Do I Know If My Child or Teen is Overweight or Obese?

  • BMI for children and teens is calculated the same way as for adults, but is interpreted differently because body fat:
    • changes with age
    • is different between girls and boys
  • Use the age and gender specific BMI calculator for children and teens. Once calculated, the number can be looked at on a CDC BMI-for-age gender-specific growth chart. Or you can use this calculator.
  • Percentiles are the most commonly used way to evaluate the size and growth patterns of individual children in the United States. A BMI percentile shows how your child's BMI compares to that of other kids their age and sex in a healthy population.

Weight status categories and corresponding percentiles are shown in the following table.

Weight Status Category Percentile Range
Underweight Less than 5th percentile
Healthy weight 5th percentile to less than the 85th percentile
Overweight 85th to less than the 95th percentile
Obese Equal to or greater than the 95th percentile

What Are the Health Consequences of Being Overweight or Obese?

  • The link between BMI and health risks is well established. Overweight and obese individuals are at increased risk for many diseases and health conditions:
    • High blood pressure (HBP) or hypertension refers to increased pressure as blood flows through the arteries. Elevated blood pressure forces the heart to work harder than normal to circulate blood throughout the body.
    • High blood cholesterol or dyslipidemia (abnormal levels of fat in the blood) occurs when levels of cholesterol (a type of fat that your body needs to work properly) and other fats in the blood are not normal. There are different types of fats in the blood, including LDL cholesterol ("bad" cholesterol), HDL cholesterol ("good" cholesterol), and triglycerides. Too much LDL and triglycerides, and too little HDL increases your risk for developing heart disease, stroke, and other circulatory problems.
    • Type 2 diabetes is a disease in which the body does not produce enough insulin and/or the body's cells have trouble using the insulin it does produce. Insulin is necessary for sugar (glucose) to be taken up by body cells for energy production. Without insulin, blood sugar levels build up in the blood. If untreated, serious complications result.
    • Coronary heart disease or coronary artery disease (CHD or CAD): CHD or CAD is the leading cause of death in the United States for men and women. It is a narrowing of the small blood vessels that supply blood and oxygen to the heart.
    • Stroke occurs when the flow of oxygen-rich blood to a portion of the brain is blocked. Without oxygen, brain cells start to die after a few minutes. There are two major types of stroke: ischemic stroke and hemorrhagic stroke. Ischemic stroke occurs when a blood vessel that supplies blood to the brain is blocked by a blood clot. These may be caused by clogged arteries from accumulation of fat, cholesterol, and other substances that collect on the artery walls, or from other causes like a blood clot traveling from elsewhere in the body to the brain. A hemorrhagic stroke happens when a blood vessel in part of the brain becomes weak and bursts open, causing blood to leak into the brain.
    • Gallbladder disease occurs when bile, which is normally stored in the gall bladder and helps digest dietary fat, becomes concentrated and thick. Gallstones are formed when bile hardens.
    • Osteoarthritis is a gradual deterioration of the joint tissue due to excessive wear and tear.
    • Sleep apnea is a condition in which breathing repeatedly stops and starts, or shallow breaths occur, during sleep because of partial or total blockage of the airway.
    • Cancer, including cancer of the esophagus, breast, endometrium, colon and rectum, kidneys, pancreas, thyroid, gallbladder, and possibly others are associated with overweight and obesity.
    • Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH) NAFLD is a condition in which fat builds up in the liver. In NASH, fat in the liver is accompanied by inflammation and fibrosis, or scarring, of the liver. NASH is an advanced form of NAFLD. NAFLD and NASH affect the liver in the same way that alcoholic liver disease does, but NAFLD and NASH occur in people who drink little or no alcohol.
    • Quality of life is an indicator of general well-being that incorporates physical and mental factors.
  • Childhood obesity is associated with:
    • a higher chance of obesity, disability and premature death in adulthood.
    • breathing difficulties, increased risk of fractures, hypertension, and risk factors for cardiovascular disease, insulin resistance and psychological effects.

Causes of the Obesity Epidemic: Understanding Energy Balance2,157

  • Many factors play a role in the development of obesity, making it a complex health issue to address. At the most basic level, it is the result of an energy imbalance. Simply stated, we eat too much and exercise too little.
  • Energy is another word for calories. Whenever you eat or drink, ENERGY (in the form of calories) is coming IN. At the same time, your body is constantly working, so ENERGY (in the form of calories) is going OUT. When you are in "energy balance" your energy (or calories) IN equals your energy (or calories) OUT.

To imagine energy balance, think of a scale...

Description: Caloric balance is like a scale. Calories in = food and beverages. Calories out = body functions and physical activity.
  • To maintain a healthy weight, your energy IN and OUT do not have to balance exactly every day. It is the balance over time that helps you maintain a healthy weight.
  • The same amount of energy IN and energy OUT over time leads to a stable weight, that is, your weight stays the same:
    • More energy IN than energy OUT over time = weight gain
    • More energy OUT than energy IN over time = weight loss
Exercise Needed to Burn Off a Serving of French Fries

Estimated Calorie Needs Per Day by Age, Gender, and Physical Activity Level7

The estimates are rounded to the nearest 200 calories. An individual's calorie needs may be higher or lower than these average estimates.

Gender Age (years) Sedentary (cal) Moderately Active (cal) Active (cal)
Child (female and male) 2-3 1,000-1,200 1,000-1,400 1,000-1,400
FEMALE a 4-8 1,200-1,400 1,400-1,600 1,400-1,800
9-13 1,400-1,600 1,600-2,000 1,800-2,200
14-18 1,800 2,000 2,400
19-30 1,800-2,000 2,000-2,200 2,400
31-50 1,800 2,000 2,200
51+ 1,600 1,800 2,000-2,200
MALE 4-8 1,200-1,400 1,400-1,600 1,600-2,000
9-13 1,600-2,000 1,800-2,200 2,000-2,600
14-18 2,000-2,400 2,400-2,800 2,800-3,200
19-30 2,400-2,600 2,600-2,800 3,000
31-50 2,200-2,400 2,400-2,600 2,800-3,000
51+ 2,000-2,200 2,200-2,400 2,400-2,800

a. Estimates for females do not include women who are pregnant or breastfeeding.

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