Optimal body weight: a practical guide

Optimal body weight isn’t one magic number on the scale. It’s a range where your health, wellbeing and everyday mobility work for you, not against you.

A simple truth: you can’t fully assess a person by height and weight alone. Still, the old formulas, body mass index and the waist-to-hip ratio give you a good starting point if you want to understand whether your body weight is heading in a sensible direction health-wise.

Why does optimal body weight matter at all?

Optimal body weight is considered to be the weight that helps a person stay in good health for as long as possible. That doesn’t mean everyone of the same height should weigh the same. Muscle mass, age, sex, training status and fat distribution change the picture quite a lot.

Back at the start of the century, insurance companies in several countries began collecting data on the relationship between body weight and lifespan. On that basis, optimal body weight tables were drawn up that took height and age into account. If body weight exceeded the “ideal weight” by 20%, a person was considered overweight. If it was 10% lower, they were considered underweight.

These tables had several weaknesses, though. Life insurance was mostly bought by wealthier people. Body weight was recorded only once – at the time of taking out the policy – and often based on the person’s own word rather than an actual weighing. So these tables are best viewed as historical background, not the final word.

How is optimal body weight calculated?

One of the best-known simple methods was Broca’s formula:

optimal body weight (kg) = height (cm) – 100

It’s convenient to work out in your head, but it isn’t very accurate for assessing a young person’s body weight. The error can be large, because the formula doesn’t take build or muscle mass into account. A trained person can look “too heavy” by this measure, even though part of the weight is muscle, not excess fat.

Today, body mass index is often used. In the original, it was written like this:

index = body weight (kg) / 2 height (M)

Body mass index is a simple screening tool. It doesn’t tell the whole story, but it helps you see whether body weight is low, suitable or too high in terms of health risk. This scale can be used for a general assessment of adult men and women.

• < 20 – low body weight can cause health problems
• 20-25 – from a health standpoint, the most suitable range for most people
• 25-27 – may in some cases cause health problems related to being overweight
• 27-30 – heavily overweight, health problems
• > 30 – obesity, serious health problems

So what actually happens? When the index goes up, the risk doesn’t change in the same way for everyone. Some people have more muscle mass, while in others fat collects mainly around the abdomen. That last one is an important warning sign for your health.

Body fat percentage and the waist-to-hip ratio

Today we look not only at body weight but also at how much of it is fat tissue. Finding body fat percentage precisely is more difficult, though. It requires specialized equipment and someone who knows how to take the measurement properly.

The skinfold caliper method has been widely used, and it rests on two principles:

• a) the thickness of the fat layer measured at different points on the body reflects the total amount of subcutaneous fat tissue;
• b) subcutaneous fat tissue is closely related to total body fat content.

The distribution of subcutaneous fat tissue is considered an important risk indicator for cardiovascular disease. Be especially watchful if fat collects around the abdomen. This is often called male-pattern fat deposition.

You can assess the waist-to-hip ratio very simply: measure both with a tape measure and compare the results. The health risk is high if the index is greater than 1.0 in men and greater than 0.8 in women. This reading reflects an increased health risk only in cases of overweight, that is, when body mass index is greater than 27.

Optimal body weight and physical activity

The human body has two main energy sources – fats and glycogen. During short, very intense training load, more glycogen is used. During longer, moderate training load, the body burns more fat. That doesn’t mean you should only train slowly, just that the type of load affects energy use.

Hormones released during training also promote fat use after the workout. Training with sufficient load can act as a metabolism booster for up to two days. Any physical load adds to energy expenditure: standing burns more energy than sitting, running more than walking.

The nature of your job matters too. With a low physical load, such as a computer operator’s, energy expenditure rises by 40-50%. With a light load, such as a teacher’s, it rises by 55-65%. With a moderate load, such as a nurse’s or a transport worker’s, it rises by 75-100% of basal metabolic rate.

How to sensibly assess your body weight

Don’t judge by a single weigh-in. Your weight fluctuates with water, food, salt and training. Look instead at the average over several weeks, how you feel, your waist circumference and how your clothes fit.

If your BMI stays between 20-25 and your waist isn’t growing, that is a good sign for most people. If your BMI is moving toward 25-27 or beyond, it is worth taking an honest look at your activity, sleep and nutrition. If the number is > 30, it is no longer just a question of appearance but a health risk, one worth tackling calmly and consistently.

FAQ: optimal body weight

Does Broca’s formula suit everyone?

No. Broca’s formula is a quick, rough calculation, but it doesn’t take age, muscle mass or build into account. You can use it as a guideline, not as a final verdict.

Does BMI show body fat percentage?

Not directly. BMI compares weight and height but doesn’t distinguish muscle from fat. That’s why it’s useful to also look at your waist-to-hip ratio and, if needed, your body fat percentage.

When should body weight be a concern?

It’s worth being concerned when your weight rises along with your waist circumference, you feel worse, or your BMI climbs above 27. In that case it makes sense to start with small, lasting changes.

Let’s get your weight sorted! ArtGym

Author: pumpiniron

Source: WHO – overweight.