The BMI formula and categories are the same after 65, but what counts as healthy shifts: in adults over 65 the risk of death is not raised in the overweight range but starts to rise below a BMI of 23, so a BMI a little over 25 is not a concern, while a low BMI or losing weight without trying is. Geriatric guidelines (GLIM, 2019) treat a BMI under 20 before age 70, or under 22 from 70, as low.
Enter your age, height and weight. If you know your weight six months ago, add it: unplanned weight loss of more than 5% in six months is one of the most important warning signs at this age.
Worked example
Age: 74 yearsHeight: 5 ft 6 inWeight now: 140 lbWeight 6 months ago: 150 lbBackground: Not Asian
Your BMI: 22.6 Healthy weight
A BMI of 22.6 is a healthy weight by the usual categories and above the low-BMI line for a 74-year-old (22). But losing 10 lb — 6.7% of body weight — in six months meets the GLIM weight-loss criterion for malnutrition, and is worth raising with a doctor.
Open this example in the calculator →How to use the BMI Calculator for Seniors
- Enter your age, then your height and weight — measure your height now, since it falls with age.
- If you know it, add your weight six months ago to check for weight loss.
- Choose your background: Asian adults have lower low-BMI lines.
- Read your BMI, the low-BMI line for your age and what the result means after 65.
What is a healthy BMI for older adults?
The WHO and CDC categories — 18.5 to 24.9 healthy, 25 to 29.9 overweight — are the same at every adult age. But research on older people points to a different sweet spot. A 2014 meta-analysis of 32 studies and almost 200,000 people aged 65 and over found that a BMI in the "overweight" range was not linked with a higher risk of death. Compared with a BMI of 23 to 23.9, risk was 12% higher at 21 to 21.9 and 19% higher at 20 to 20.9, and it began to rise again above a BMI of 33.
That does not mean older adults should gain weight, and it does not apply to someone with diabetes or heart disease who has been told to lose weight. It means that, after 65, weight in the low 20s and falling is often a bigger concern than weight a little over 25.
BMI for seniors at a glance
| BMI | Usual category | What it means after 65 |
|---|---|---|
| Below 18.5 | Underweight | Low at any age — see a doctor |
| 18.5 to 19.9 (to 21.9 from age 70) | Healthy weight | Low for an older adult by the GLIM criteria — check for malnutrition |
| 20 (or 22) to 22.9 | Healthy weight | Risk of death slightly raised in large studies; watch for weight loss |
| 23–29.9 | Healthy / Overweight | Not linked with a higher risk of death after 65 |
| 30–32.9 | Obesity class 1 | Risk of death not raised; joints and mobility may benefit from careful weight loss |
| 33 or more | Obesity (class 2 from 35) | Risk rises; weight loss with strength training is usually advised |
The low-BMI line is from the Global Leadership Initiative on Malnutrition (GLIM). For Asian adults GLIM uses 18.5 before 70 and 20 from 70. The other rows summarise Winter et al. (2014).
Why weight loss matters more than the number
An older adult who loses weight without trying loses muscle along with fat. That raises the risk of falls, fractures, infections and slow recovery from surgery — the cluster of problems called frailty. GLIM counts losing more than 5% of body weight in six months, or more than 10% over a longer period, as a sign of malnutrition. For a 150 lb person, 5% is 7.5 lb. Common causes include illness, depression, dental problems, medicines that dull the appetite and difficulty shopping or cooking — many of them treatable.
Why BMI is less accurate after 65
- Height shrinks. Most people lose 1 to 3 inches by their 70s as spinal discs compress. Using your younger height makes your BMI look lower than it is, so measure it.
- Muscle turns to fat. The same BMI hides more fat and less muscle at 75 than at 35 (sarcopenia). A waist measurement and grip strength say more.
- Curvature of the spine can make height impossible to measure accurately. Doctors then estimate it from arm span or knee height.
Healthy weight after 65: what helps
Most geriatric advice comes down to keeping muscle: strength or resistance exercise two or more days a week, protein at every meal (older adults need more than younger ones — often around 1 to 1.2 g per kg of body weight a day), and staying active. If weight loss is advised, it should be slow and paired with exercise. The BMR calculator shows how many calories your body uses at rest.
Frequently asked questions
What is a healthy BMI for a 70-year-old?
The standard healthy range is 18.5 to 24.9, but for adults over 65 research finds no extra risk of death across a BMI of about 23 to 33, with risk rising below 23. Geriatric criteria (GLIM) treat a BMI under 22 at 70 or older as low.
Is it bad to be overweight after 65?
A BMI of 25 to 29.9 is not linked with a higher risk of death in adults over 65, and may protect against frailty. Obesity, especially above a BMI of about 33, still raises risks, and losing weight can help joints and mobility. A doctor can weigh it against your other conditions.
What BMI is too low for an elderly person?
Under the GLIM criteria, a BMI under 20 for someone younger than 70, or under 22 for someone 70 or older, is low and a sign to check for malnutrition. For Asian adults the lines are 18.5 and 20.
How much weight loss is concerning in older adults?
Losing more than 5% of body weight in six months without trying — about 7 to 8 lb for a 150 lb person — or more than 10% over a longer period. It is worth a doctor’s visit even if the BMI is still in the healthy range.
Does BMI change with age?
The formula and categories do not. But body composition does: older adults have less muscle and more fat at the same BMI, and lose height, which can make BMI misleading. That is why low weight, weight loss and waist size are watched more closely than BMI after 65.
Should seniors try to lose weight?
Only with care. For an older adult with obesity, slow weight loss combined with strength exercise improves mobility and blood sugar without losing much muscle. For someone at a normal or overweight BMI with no weight-related illness, keeping weight stable and staying strong is usually the better goal.
Sources
- Winter JE et al. BMI and all-cause mortality in older adults: a meta-analysis. Am J Clin Nutr 2014;99:875–890 — American Journal of Clinical Nutrition
- Cederholm T et al. GLIM criteria for the diagnosis of malnutrition. Clin Nutr 2019;38:1–9 — Clinical Nutrition
- Obesity and overweight (fact sheet) — World Health Organization
- Adult BMI Categories — Centers for Disease Control and Prevention
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 1991;65:105–114 — British Journal of Nutrition
- Overweight and obesity management (NG246), 2025 — National Institute for Health and Care Excellence (UK)
For general information only — not a diagnosis or a substitute for advice from a doctor. How we calculate.