Reaching and maintaining a healthy weight is essential for overall health and can help you prevent and control many diseases and conditions.

If you are overweight or obese, you are at higher risk of developing serious health problems, including heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.

That is why maintaining a healthy weight is so important: It helps you lower your risk for developing these problems, helps you feel good about yourself, and gives you more energy to enjoy life.

What Is Overweight and Obesity?

Overweight has extra body weight from muscle, bone, fat, and water. Obesity is having a high amount of excess body fat.

Body mass index (BMI) is a useful measure of overweight and obesity. Here, we will provide you with information about BMI (including limitations of this measure) and how to reach and stay at a healthy weight.

Talk to your health care provider if you are concerned about your BMI.

What Factors Contribute To a Healthy Weight?

Many factors can contribute to a person’s weight. These factors include environment, family history and genetics, metabolism (how your body changes food and oxygen into energy), and behavior or habits.

Energy Balance

Energy balance is essential for maintaining a healthy weight. The amount of energy or calories you get from food and drinks (energy IN) is balanced with the energy your body uses for things like breathing, digesting, and being physically active (energy OUT):

• The same amount of energy IN and energy OUT over time = weight stays the same (energy balance)
• Weight gain if energy IN more than energy OUT
• Weight loss if energy OUT more than energy IN

Your energy IN and OUT doesn’t have to balance exactly every day to maintain a healthy weight. Instead, it’s the balance over time that helps you maintain a healthy weight.

You can reach and maintain a healthy weight if you:

• Follow a healthy diet, and if you are overweight or obese, reduce your daily intake by 500 calories for weight loss
• Are physically active
• Limit the time you spend being physically inactive

Assessing Your Weight and Health Risk

Assessment of weight and health risk involves using three key measures:

1. Body mass index (BMI)
2. Waist circumference
3. Risk factors for diseases and conditions associated with obesity

Body Mass Index (BMI)

BMI is a useful measure of overweight and obesity. It is calculated from your height and weight. BMI is an estimate of body fat and a good gauge of your risk for diseases with more body fat. The higher your BMI, the higher your risk for specific conditions such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.

Although BMI can be used for most men and women, it does have some limits:

• It may overestimate body fat in athletes and others who have a muscular build.
• It may underestimate body fat in older persons and others who have lost muscle.

Use the BMI Calculator or BMI Tables to estimate your body fat. The BMI score means the following :

	BMI
Underweight	Below 18.5
Normal	18.5–24.9
Overweight	25.0–29.9
Obesity	30.0 and Above

Waist Circumference

Measuring waist circumference helps screen for possible health risks that come with overweight and obesity. For example, if most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes. This risk goes up with a waist size greater than 35 inches for women or greater than 40 inches for men. To correctly measure your waist, stand and place a tape measure around your middle, just above your hipbones. Then, measure your waist just after you breathe out.

The following is a table of Risks for Obesity-Related Diseases by BMI and Waist Circumference that provides you an idea of whether your BMI combined with your waist circumference increases your risk of developing obesity-related diseases or conditions.

Classification of Overweight and Obesity by BMI, Waist Circumference, and Associated Disease Risks

			Disease Risk* Relative to Normal Weight and Waist Circumference
	BMI (kg/m2)	Obesity Class	Men 102 cm (40 in) or less Women 88 cm (35 in) or less	Men > 102 cm (40 in) Women > 88 cm (35 in)
Underweight	< 18.5		–	–
Normal	18.5–24.9		–	–
Overweight	25.0–29.9		Increased	High
Obesity	30.0–34.9	I	High	Very High
	35.0–39.9	II	Very High	Very High
Extreme Obesity	40.0 +	III	Extremely High	Extremely High

* Disease risk for type 2 diabetes, hypertension, and CVD.
+ Increased waist circumference also can be a marker for increased risk, even in persons of average weight.

Risk Factors for Health Topics Associated With Obesity

Along with being overweight or obese, the following conditions will put you at greater risk for heart disease and other conditions:

• High blood pressure (hypertension)
• High LDL cholesterol (“bad” cholesterol)
• Low HDL cholesterol (“good” cholesterol)
• High triglycerides
• High blood glucose (sugar)
• Family history of premature heart disease
• Physical inactivity
• Cigarette smoking

Source: National Heart, Lung, and Blood Institute (NIH)