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BMI? Is This Really an Accurate Way to Monitor Weight?

The new BMI guidelines have caused some commotion as to whether these changes have been made were entirely necessary, but in truth BMI has long been a controversial method of measuring weight and obesity as the results can be extremely misleading.

The new BMI guidelines have caused some commotion as to whether these changes have been made were entirely necessary, but in truth BMI has long been a controversial method of measuring weight and obesity as the results can be extremely misleading.

BMI, (which is calculated by considering both weight and height) does offer a rough guideline as to whether a person is over or underweight, but it should never exist as a standalone method of assessing ideal body weight.

A number of measures must be implemented simultaneously to draw an absolute conclusion as to whether a person is at the correct weight for both build and height.

I want to outline the methods of measuring a healthy weight and consider the relevance BMI and the scales can play when implemented alongside these other, more critical factors.

These are the techniques we use to great affect in our London Health and fitness studio


Body composition is the single most important factor in determining whether an individual is overweight.

The fitness industry has long considered body composition the most important factor in determining whether an individual is overweight, but it has never gained the mainstream popularity of BMI owing to the complexity of gaining an accurate reading.

Body composition, or body fat percentage, relates to the relation of quality body mass (muscle, tissue, bone and water) versus body fat. Low body fat is what gives the body the attractive appearance of firm and toned muscles.

In males, anything less than 20% body fat would be considered healthy, whilst in females anything under 25% indicates healthy body fat levels.

Bioelectrical Impedance can never be considered accurate, so the best available method of measurement is by way of skin fold measurements taken using specialist calipers.

We strongly recommend you visit an experienced professional should you want an accurate reading, but if you want to do it yourself, this link offers an excellent and simple method to follow along with calculation tools.


By taking measurements of key areas on your body you determine not only whether a particular area is too large in absolute terms, but also which areas are disproportionately large, a far more important consideration.

For instance, in women, a waist to hip ratio is a key determinant of attractiveness as well as being an important health indicator.

0.7 is considered the ideal waist to hip ratio in women and anything over 0.8 is the point at which health is considered compromised.

In men the waist to chest ratio, not only offers an accurate reflection of the perceived attractiveness to women (the classic v-shape) but is also a key indicator of health issues such as heart disease and diabetes.

In a number of studies 1.4, chest to waist, emerged as a more attractive ratio in numerous studies, whilst anything less than 1.1 suggests poor health could be present.

If you wish to take measurements in order to assess your health and weight, the areas you should measure are.

Waist - Around belly button

Hips - Around hip-bone

Chest - Around nipples

Right arm - Mid-point between arm pit and elbow crease

Right Thigh - Mid-point between groin area and knee joint.


When looking in the mirror it is easy to over or under-estimate our weight. The mirror can be deceitful to our eyes, often projecting the image we imagine rather than the actual reality.

Whilst you often hear of the person viewing holiday snaps with unexpected horror, it is equally common for people to perceive themselves as overweight when in fact they are severely underweight.

A photograph never lies, and is an important tool when it comes to self-perception.

At our personal training studio, we will always take photographs of our clients before and after they undertake a health regime, and when checked against after 8 weeks of improved nutrition and training they are frequently astonished at the change that is demonstrated in a way the other biometrics could never reveal.

A photograph may not be as useful for determining initial weight as Body composition or even BMI, but can often be a more revealing method of monitoring progress and creating a realistic body self-image.

BMI as a factor.

So with the measures taken above, does there remain relevance for BMI and scales in measuring ideal weight?

Well, yes there does, but it is very much secondary and driven by the aesthetic preference of the individual.

Caution: It is important not to become obsessed with the number on the scales, especially when understanding the higher importance of both body fat and measurements, but it is useful to understand the role they play.

To demonstrate, the statistics below are of two women with all factors the same with the exception of weight.


Woman 1

Height 5'3"

Weight 70kg

Body fat percentage 15%

Waist to Hips 0.7

Woman 2

Height 5'3"

Weight 60kg

Body fat percentage 15%

Waist to Hips 0.7

In woman 1, although her BMI would be high, she would not be considered overweight as she has very healthy body fat levels and an ideal Waist to hip ratio. She would possess the appearance of a power or weightlifter though, and this may not be a desirable physique.

In woman 2, all factors are identical to woman 1 with the exception of weight, creating a lower BMI and entirely changing the aesthetics. This woman would now appear more towards the most socially accepted appearance of a bikini model or hollywood actress.

The most important point here is that I would not consider woman 1 more/less overweight or healthy than woman 2 despite the huge difference in BMI. I would however suggest woman 2 would be more in keeping with the desired physique of the majority of women.

By taking all of above factors into account, you can be certain to ascertain the most accurate reflection of whether you are under, over or at your ideal weight. BMI alone will never give you the full picture.