Healthy weight

What is it?

According to the NHLBI, a healthy weight for adults is generally when body mass index (BMI) falls between 18.5 and 24.9, and it advises always asking a healthcare provider what this number means for you.

The CDC calculates body mass index by dividing weight in kilograms by the square of height in metres (kg/m²), describes it as a quick, safe and reliable screening tool for estimating weight relative to height, and stresses that it is viewed together with other factors when assessing an individual's health.

The World Health Organization defines overweight in adults as a body mass index of 25 or more, and obesity as an index of 30 or more, and describes obesity as a chronic disease.

MedlinePlus says that reaching and maintaining a healthy weight rests on a balance between food and activity, and that a healthcare provider can determine the healthy weight that suits you.

Why it matters

The NHLBI states that the more body fat and weight, the greater the chance of heart disease, high blood pressure, type 2 diabetes, breathing problems and some types of cancer.

MedlinePlus adds that excess weight raises the risk of many health conditions such as type 2 diabetes, heart disease, kidney disease and some cancers, and that a healthy lifestyle reduces the chance of weight-related conditions.

According to the World Health Organization, a BMI higher than optimal caused an estimated 3.7 million deaths in 2023, with increased deaths from diseases such as cardiovascular disease, diabetes and cancers. The organisation states that 1 in 7 people in the world (1.1 billion) were living with obesity in 2024.

The CDC says modest weight loss for someone who is not at a healthy weight may improve blood pressure, cholesterol and blood sugar, and may lower the risk of some chronic diseases such as heart disease, prediabetes and type 2 diabetes.

The World Health Organization stresses that overweight and obesity and the related noncommunicable diseases are largely preventable and manageable.

Key points

BMI categories for adults (20 years and over) according to the CDC: below 18.5 underweight; 18.5 to below 25 healthy weight; 25 to below 30 overweight; 30 or above obesity. The CDC divides obesity into three classes: class 1 from 30 to below 35, class 2 from 35 to below 40, and class 3 (severe obesity) 40 or above. It says these categories apply to adults regardless of age, sex or race.

The World Health Organization uses for adults: overweight at an index of 25 or more, and obesity at 30 or more, and states that the categories defining overweight and obesity differ by age and sex between adults, adolescents, children and infants.

The limits of the index according to the CDC: it does not directly measure body fat, does not distinguish between fat, muscle and bone, and does not show the type of fat or where it is concentrated in the body. For a fuller picture the CDC advises looking alongside it at the medical history, health habits (diet, activity and sleep), clinical examination findings (such as blood pressure and muscle mass) and tests (such as glucose and cholesterol).

Waist circumference: the World Health Organization states that other measurements such as waist circumference can also be used to determine overweight or obesity. According to the NHLBI, if most fat is concentrated around the waist rather than the hips the risk of heart disease and type 2 diabetes is higher, and a waist circumference of more than 35 inches (about 89 cm) for women or more than 40 inches (about 102 cm) for men raises the risk (figures in inches as given in the source).

How to measure the waist according to the NHLBI: stand and place the measuring tape around your middle just above your hip bones, and measure right after breathing out.

Weight loss goals according to the NHLBI: for someone diagnosed with overweight or obesity specialists recommend losing 5% to 10% of initial weight over about 6 months. Even before reaching that, losing 3% to 5% of current weight may lower triglycerides and blood glucose and the risk of type 2 diabetes, and losing more than 3% to 5% may improve blood pressure readings, lower "bad" LDL cholesterol and raise "good" HDL cholesterol.

The pace of loss according to the CDC: people who lose weight at a steady gradual pace, about 1 to 2 pounds a week (roughly half a kilogram to one kilogram), are more able to maintain the result than those who lose it faster. A CDC example: a 5% loss for a person weighing 200 pounds (about 91 kg) equals 10 pounds (about 4.5 kg).

Activity: MedlinePlus states that the general recommendation for adults is 150 minutes of physical activity a week, which can be split into short periods across the day.

How to put it into practice

Diet according to MedlinePlus: to lose weight you need to eat fewer calories than you use. Ways include: eating more nutrient-rich foods (vitamins, minerals and fibre), cutting down on foods and drinks high in calories, salt, sugar and fat, limiting alcohol, and cooking in healthier ways such as using healthier oils and baking or grilling instead of frying. And see healthy nutrition.

The CDC states that eating more fruit and vegetables may help you feel full without adding many calories, that limiting added sugars may improve health, and that drinking enough water every day is important.

Movement: MedlinePlus advises increasing physical activity of both kinds: aerobic, which works the large muscles and raises heart rate and breathing, and muscle-strengthening exercises. The CDC states that walking is often a good way to add more activity to your day. And see physical activity.

Sleep and stress: MedlinePlus says that people who do not get enough sleep may eat more calories and snack more. The CDC suggests for someone who feels tired from lack of sleep: regular times for bed and waking, avoiding caffeine in the afternoon and evening, and switching off electronic devices at least 30 minutes before bed. And see sleep.

The CDC's five-step plan: (1) know your reason, write it down and keep it in front of you daily; (2) record where you are now: everything you eat and drink for a few days, your activity and its duration, your hours of sleep, and your ways of relieving stress; (3) set specific, realistic goals, and focus on two or three at a time; (4) look for support from family and friends, a weight loss programme, or a health professional such as a dietitian; (5) review your progress regularly and reward yourself with non-food rewards.

CDC examples of short-term goals: drinking water instead of sugary drinks, walking 15 minutes in the evening, or adding vegetables to dinner. An example of a specific goal: "I will walk 15 minutes, 3 days a week during the first week". The CDC states that occasional setbacks are expected, and what matters is getting back on track quickly.

Lifelong prevention according to the World Health Organization: a healthy diet rich in fruit, vegetables, legumes, whole grains and nuts while limiting foods high in fat, sugar and salt, limiting sugar-sweetened drinks and energy-dense, nutrient-poor foods, regular physical activity throughout life, enough sleep and support for mental health, and avoiding tobacco and harmful use of alcohol.

Maintaining weight: MedlinePlus states that weighing yourself regularly helps you notice small changes early, and that sometimes slipping back into old habits is normal; what matters is returning to your healthy habits and carrying on.

Special groups

Children and adolescents (2 to 19 years) according to the CDC: because they are growing, BMI-for-age percentiles by age and sex are used: below the 5th percentile underweight; 5th to below the 85th percentile healthy weight; 85th to below the 95th percentile overweight; 95th percentile or above obesity; and severe obesity at 120% of the 95th percentile or more, or a BMI of 35 kg/m² or more. The CDC describes BMI calculators as screening tools for estimating weight status.

The NHLBI states that a child's body mass index is compared with growth charts specific to age and sex, and advises talking to the child's healthcare provider to find out whether their weight is healthy.

The World Health Organization uses a different reference: for ages 5 to 19, overweight is when BMI-for-age is more than one standard deviation above the median of the WHO growth reference, and obesity when it is more than two standard deviations. Under 5 years: overweight is when weight-for-height is more than two standard deviations above the median of the WHO child growth standards, and obesity when it is more than 3 standard deviations. The child's doctor decides which reference is used.

The organisation says overweight and obesity in childhood and adolescence harm physical, psychological and social health, and are linked to stigma, bullying and reduced school performance, and obesity often persists into adulthood without early intervention. It recommends supporting healthy eating, activity, good sleep and limiting inactivity and screen time during childhood and adolescence, and exclusive breastfeeding in the first six months and continuing until the age of two or more.

Pregnancy: according to the CDC the recommended weight gain in pregnancy is based on pre-pregnancy body mass index. For a single baby the Institute of Medicine recommendations mention (figures in pounds as given): underweight (below 18.5) 28 to 40 pounds (about 12.5 to 18 kg); normal weight (18.5–24.9) 25 to 35 pounds (about 11.5 to 16 kg); overweight (25.0–29.9) 15 to 25 pounds (about 7 to 11.5 kg); obesity (30.0–39.9) 11 to 20 pounds (about 5 to 9 kg). The figures differ in a twin pregnancy, and the CDC advises working with a healthcare provider on the weight gain target and monitoring it.

The World Health Organization lists among prevention steps reaching a healthy weight before pregnancy and ensuring appropriate weight gain during it. Each pregnant woman's plan is for her doctor, see obstetrics and gynaecology.

Risks and cautions

Fad diets: the CDC says fad diets promise quick results, but restrict the nutrients you get, may be unhealthy, and tend to fail in the long term.

Unrealistic goals: the CDC states that goals such as losing 20 pounds (about 9 kg) in two weeks may leave you discouraged, and that people who lose weight faster are less able to maintain it than those with a gradual pace.

Medicines and health conditions: MedlinePlus states that some medicines such as steroids and some antidepressants may lead to weight gain, and that some chronic conditions such as Cushing's syndrome and polycystic ovary syndrome may cause weight gain. Do not stop any medicine on your own; the CDC advises talking to a healthcare provider if you have concerns about your weight or questions about your medicines.

Before starting: MedlinePlus advises seeing a healthcare provider first before starting a diet or weight loss programme, so they can determine the healthy weight for you and help you set goals.

Unintentional weight loss: MedlinePlus defines it as losing weight without trying to, and advises contacting a healthcare provider if you have lost more than 10 pounds (4.5 kilograms) or 5% of your usual weight within 6 to 12 months or less for no known reason, or if the weight loss comes with other symptoms.

Limits of this information

This page is about healthy weight and prevention. As for treating obesity as a disease, including the medicines and surgery that MedlinePlus says a provider may turn to if lifestyle change is not enough, its place is the obesity page, and the decision on it is made by the doctor.

The CDC and NHLBI figures are American in origin, and waist circumference, pregnancy weight gain and pace of loss figures appeared in US units (inches and pounds) as in the sources, and what is in brackets in centimetres and kilograms is an approximate conversion we added for convenience. The reference for children differs between the CDC and the World Health Organization. The weight, goal and pace of change that suit you are decided by your doctor according to your condition.

This page does not specifically cover older people, the risks of being underweight, the medical complications of rapid weight loss, waist circumference thresholds for different populations, or signs that need immediate emergency care.

The World Health Organization fact sheet is dated 7 October 2026, and its figures may change in later updates.

Common questions