What is your ideal weight and does it change as you get older?
What should I weigh? It's one of the most common questions in health and fitness. Many people hope for a simple answer: an accurate number that shows that their body is where it should be.
But the truth is, your ideal weight is probably not a single weight. It's a range where you have a good balance between fat mass and muscle mass, a healthy metabolism, and a body that functions in everyday life.
And the older we get, the less the scale tells us on its own.
The scale only shows how much the body weighs.
Two people can weigh the same and be the same height – but have completely different health.
One person may have plenty of muscle mass, relatively little belly fat, and good fitness. The other may have less muscle and more fat around the internal organs. The scale sees no difference. It weighs muscle, fat, bone, and fluid in the same package.
Therefore, a better definition of ideal weight is.
The weight or weight range where you have enough muscle, a healthy amount of body fat, a small amount of harmful belly fat, and good physical function – without having to live on an extreme diet to stay there.
How useful is BMI?
BMI is calculated by dividing weight in kilograms by height in meters squared. According to the WHO, a BMI of 25 or higher is considered overweight and a BMI of 30 or higher is considered obese. The so-called normal range is usually stated as 18.5–24.9. At the same time, the WHO emphasizes that BMI is only an indirect measure of body fat and that, for example, waist circumference is needed for a better assessment. WHO: Obesity and overweight BMI is thus a useful first filter at the population level, but a rather blunt tool for the individual. It does not distinguish between muscle and fat. A well-trained person can therefore have a high BMI without having a lot of body fat. Conversely, a person can have a “normal” BMI but still carry a lot of abdominal fat and have too little muscle mass.
The conclusion is not that BMI is useless. The conclusion is that BMI should never stand alone.
The waist tells you things that the scale misses
The fat around the belly – especially the visceral fat around the internal organs – is more linked to type 2 diabetes, cardiovascular disease and metabolic ill health than fat located on the hips and thighs, for example.
A simple measure is therefore waist to height.
A practical rule of thumb is to try to keep your waist measurement below half your body length. If you are 180 centimetres tall, this means a waist measurement below around 90 centimetres. NICE classifies a waist-to-height ratio below 0.5 as the level you should aim for to reduce health risks. NICE: Identifying and assessing overweight, obesity and central adiposity
This is not a perfect limit, but for many it is more informative than weight alone.
Does ideal weight change as we get older?
Yes or rather: what is most important changes. With As we age, we tend to lose muscle mass and strength, while our body fat percentage can increase. This means that our weight can remain completely stable while our body slowly changes in the wrong direction. The same weight at 65 as at 45 does not necessarily mean the same body.
The dangerous combination is a lot of fat and too little functioning muscle mass – so-called sarcopenic obesity. An international expert group from ESPEN and EASO describes the condition as simultaneous excess fat and low muscle mass or muscle function. The group emphasizes that the assessment needs to include both fat mass and physical function, not just BMI. ESPEN/EASO: Definition and Diagnostic Criteria for Sarcopenic Obesity
For older people, it is therefore risky to chase a low weight at all costs.
A strict diet can reduce both fat and muscle. The result can be a lower number on the scale but also poorer strength, balance and resilience.
Research also shows that the relationship between BMI and mortality looks different in older people than in younger people. A meta-analysis of almost 200,000 people over 65 found an increased risk of mortality at a BMI below 23, while BMI in the normal overweight range was not linked to the same increase in risk. This does not prove that extra body fat is protective – illness, frailty and involuntary weight loss can affect the results – but it shows why older people should not be pressured to achieve a low BMI without considering muscle and function. Winter et al.: BMI and all-cause mortality in older adults
After 60, the goal should therefore often be.
to reduce abdominal fat if it is too high
to maintain or increase muscle mass
to maintain strength, balance and mobility
to avoid rapid or involuntary weight loss
to find a weight that is sustainable with a normal and nutritious life
Is there an optimal fat percentage?
Not one specific one that applies to everyone. Women naturally need a higher fat percentage than men, and body fat tends to increase with age. In addition, different measurement methods can give different results. A smart scale with bioimpedance can vary several percentage points depending on fluid, food, exercise and time of day. Therefore, a single measurement is never the whole truth.
The following ranges are often used as approximate healthy reference ranges. They are based on research linking body fat to established BMI limits – they are not proven “maximum lifespan zones”. Gallagher et al: Healthy percentage body fat ranges
Age | Men | Women |
20–39 years old | approximately 8–19% | approximately 21–32% |
40–59 years | approximately 11–21% | approximately 23–33% |
60–79 years | approximately 13–24% | approximately 24–35% |
See the ranges as a guide, not as a grade. Someone who is in the middle of their range, has a reasonable waist size, good strength and good blood values rarely needs to chase further fat loss for the sake of health.
Very low body fat is not automatically healthier. What looks impressive on stage or in a social feed can be difficult to maintain and can affect hormones, energy, sleep, immune system and exercise capacity for some. “As little fat as possible” is therefore not a good health goal.
How to find your own healthy weight
View multiple markers at once:
Weight and weight trend – not just today's number, but the direction over months and years.
Waist measurement – preferably in relation to length, with under 0.5 as a simple rule of thumb.
Body composition – follow the trend using the same measurement method and under similar conditions.
Strength and function – can you easily get up from a chair, walk briskly, carry grocery bags and maintain your balance?
Health values – blood pressure, blood sugar, blood lipids and other relevant tests.
How to maintain weight – if it requires constant hunger and extreme control, it is probably not ideal for you.
If the waistline decreases, strength remains or improves, and health values are moving in the right direction, the body can become significantly healthier even if the scale moves slowly.
My conclusion
Your ideal weight is not necessarily the lowest weight you can achieve. It is the weight where your body functions best and where you can be strong, mobile, and metabolically healthy over time.
When we're younger, we often get away with focusing on pounds. As we get older, we need to think smarter: less harmful belly fat, more functioning muscle mass, and a body that can handle life.
So don't just ask:
“What should I weigh?”
Also ask:
“How much of my weight helps me live – and how much works against me?”
That's where the real ideal weight is.
All the best, Kennet Båth
The text provides general health information. Involuntary weight loss, obvious weakness or planned major weight loss in old age or chronic illness should be assessed together with healthcare.
