Health Topic

Body Weight

Body weight is the total mass of your body. Keeping track of your weight is one way to check for changes in your health, but it can't tell you the whole story.

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Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Body Weight

Body weight is the total mass of your body. Keeping track of your weight is one way to check for changes in your health, but it can't tell you the whole story. That's because your weight includes muscle, bone, fat, and water. Also, everyday factors can play a role in your weight, such as your:

  • Diet
  • Activity level
  • Stress level
  • Sleep habits
  • Family history and genetics
  • Age

A healthy weight is more than just a number on the scale. It's about feeling good, having energy, and lowering your risk of disease. Your health care provider can help you determine a healthy body weight based on several factors. These include your:

  • Body Mass Index (BMI). BMI is a measure of how much you weigh compared to how tall you are. The higher your BMI, the higher your risk for certain diseases. BMI does not distinguish between fat, muscle, and bone mass. It also may overestimate body fat in athletes or those with a muscular build, or underestimate body fat in older persons or others who have lost muscle.
  • Waist circumference. If most of your body fat is around your abdomen (belly) rather than your hips, you may be at a higher risk for heart disease and type 2 diabetes.
  • Health history. Your health care provider will likely consider your risk factors for diseases and health conditions, such as having high cholesterol, in determining your healthy body weight.

Having a healthy body weight may lower your chance of developing certain health problems. Carrying too much or too little weight can affect your health. Ranges of body weight include:

  • Underweight. Your weight is lower than it should be for your health.
  • Normal. Your weight is within a healthy range.
  • Overweight. Your weight is greater than it should be for your health.
  • Obese. Your body fat is greater than it should be for your health.

Body weight needs can be different at different ages. For children, weight and growth are tracked over time based on their age. For older adults, keeping muscle and strength is key, and sudden weight loss should always be checked by your provider.

Talk to your provider if you're losing or gaining weight without trying. A sudden, unexpected change in weight can be a sign of a medical problem.

Causes for sudden weight loss can include:

  • Thyroid problems
  • Cancer
  • Infectious diseases
  • Digestive diseases
  • Certain medicines

Causes for sudden weight gain can include:

  • Certain medicines
  • Thyroid problems
  • Heart failure
  • Kidney disease
  • Liver disease

Maintaining a healthy body weight can improve energy, sleep, and overall wellbeing. Talk to your provider about what a healthy weight would be for you. If they recommend that you gain or lose weight, they might refer you to a dietician for support. A dietician is a professional who has special training to help you learn the best way to eat.

  • Good nutrition and exercise can help in losing weight. Even a small change in weight can lower your risk of developing certain diseases.
  • Eating extra calories within a well-balanced diet and treating any underlying medical problems can help you gain weight.

Focus on your health, not just the number on the scale. With daily healthy habits and self-compassion, you can support lasting improvements in your overall wellbeing.

It sits within Food and Nutrition and Metabolic Problems.

The lead U.S. institute for this subject is the National Heart, Lung, and Blood Institute.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Body Weight

17,165 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Related Issues

Statistics and Research

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Body Weight Changes, Body Weight. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Body Weight, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.