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5 reasons why BMI and body weight are inaccurate measures of your health and 3 simple alternatives

With obesity affecting 28% of UK adults and another 36% of UK adults considered overweight*, how we measure our bodies within the context of our overall health has become even more important. 

*Source: Health Survey for England 2019

3 Reasons why BMI is an inaccurate measure of health

1. The BMI formula is flawed

The formula for BMI was created almost 200 years ago by mathematician Lambert Adolphe Jacques Quetelet. He created the formula as a quick and easy way to identify obesity in the general population, not for individuals. The formula is your weight in pounds divided by your height in inches. This doesn’t consider waist size which is a key indicator of a person’s health. Lambert himself stated that this formula “could not and should not be used to indicate the level of fatness in an individual”.

2. BMI doesn’t account for factors influencing your overall health

Body composition factors such as bone density and lean muscle mass are not taken into account with BMI. Therefore, people with strong and dense bones, lean muscle and low body fat can have a high BMI. They can be labelled as overweight or obese when in fact they’re actually healthy. Even professional athletes have been deemed “overweight” or “obese” by the BMI.

3. BMI doesn’t account for the distribution of fat in your body

BMI fails to address where body fat is distributed in the body. This information provides important insight into potential health risks. I.e. high proportion of fat distributed around the stomach area is associated with resistance to insulin and the development of diabetes as well as heart disease.

Why body weight is a measure of success is deceptive 

Body weight is still a commonly used metric for success in a fitness programme. But as I often tell our members, it isn’t the best metric to assess your progress. The reasons for this are two-fold: 

1. Measuring only body weight lacks insight

Weight in and of itself doesn’t provide any information about health. You can go down the road of ‘ideal weight for height’ (which then becomes BMI), but the problem with this theory is it assumes that we are all the same shape and size. Due to ethnic and sex differences alone, we are not all created equal. So, to attempt to pigeon-hole ‘ideal weight’ without accounting for the individual nature of your body type and shape is deceiving. 

2. Measuring only body weight hides potential health issues

If you regularly exercise without allowing for sufficient recovery, you can start to collect body fat around your middle. (This is often referred to as being ‘skinny-fat’). But if you weigh yourself on the scale, you may see your weight decreasing and be led to believe you’re improving your health – unaware that your muscle could be reducing and your body fat increasing. Not a good direction to be heading in!

3 simple alternatives to effectively assess your health at home

If BMI and body weight do not make good measures for health, what does? Here are 3 simple ways you can assess your body composition and general health.  

1. Check how your clothing fits

Try on a piece of clothing that doesn’t fit – then 30 days later, try it on again.

When you’re exercising regularly, eating well and recovering properly, your body will start to shrink all over.

By using a piece of clothing as a measurement tool, you can get a real-life assessment of how your body is changing in real time. No confusing numbers, no obscure calculations, just the answer to a simple question: does it fit or doesn’t it?  

If it does fit better than before, then you know you’re doing the right things. If it doesn’t, it’s time to consider changing course or seeking professional help. 

2. Measure your waist to hip ratio

The waist measurement is often used as a window into potential health risks. This is because excess body fat around the stomach reflects the risk of diabetes, as well as cardiovascular and respiratory conditions. 

The notion is straightforward. Measure your waist at the belly button so you have a consistent landmark to measure it each time. Measure your hips at the top of your hip bone.

To calculate your waist to hip ratio, divide your waist size by your hip size. I.e. for a waist size of 83cm and a hip size of 93cm;

83cm/93cm = 0.89 

For women a healthy waist to hip ratio is 0.80 or less.

For men a healthy waist to hip ratio is 0.94 or less.

Repeat this measurement every 30 days. If your waist is expanding, it’s time to examine your eating and sleeping patterns. If your waist size is decreasing, you’re probably on the right track to improving your health. 

3. Ask yourself how you feel in the morning

When you open your eyes in the morning, do you feel refreshed? Or are you wearing out the snooze button because you feel consistently groggy? While this can be symptomatic of a variety of issues, if you’re exercising on regularly, it can indicate over-training. 

We’re all pressed for time, and the thought of missing a workout because you’ve woken up knackered may seem like you’re not putting in enough effort, especially if your schedule is busy and you really want to squeeze it in.  

But it’s important to listen to the signals your body provides when it comes to making workout decisions. If you listen to your body and take it slightly easier on the days you feel tired, you’ll recover more effectively and come back stronger. 

The point is this – don’t rely on metrics that are based on a broad survey. By using personalised measures like these listed here, you’ll get a better sense of whether your efforts are benefiting you specifically. This will help you to make long-lasting change and progress. 

styku 3D body scan & Health review

We’ve given you 3 simple ways to provide you with a rough guide on your health and your body composition at home.

When you join a Fit to Last programme, we use the Styku 3D Body Scan & Health Review to accurately track your progress towards your health and fitness goals.

Styku™ is a full-body health scanning technology that maps the shape, composition, and health of your body, using the latest in computer vision and artificial intelligence.

This equipment gives you the ability to perform a full body scan, view 3D models of yourself, extract your body circumferences, predict your body composition, estimate your health risks, set yourself realistic fitness goals, track changes in your body shape, and much more.



The 3D Body Scan takes 30 seconds to complete:

  1. Step onto the platform.
  2. Stand still whilst the platform rotates for a few seconds.
  3. Once scanning is complete, step off the platform to review your results with our fitness professional.

Our fitness professional will review your results together with you. The results of your scan are also emailed to you and include:

  • 3D image of your body
  • Your body composition statistics
  • Your health review
  • Your posture assessment
  • Your fitness goals


When you join a Fit to Last programme, the Styku 3D Body Scan & Health Review is the tool we we use to track your progress and is included in your programme.

You may already be following a fitness regime of your own, or even if you don’t have one – we can still help you. The 3D Body Scan & Health Review will give you clarity on your starting point, setting realistic fitness goals or tracking your progress.


To schedule in your 3D Body Scan, simply get in touch.
The investment required for a 3D Body Scan and Health Review is £49.00.


James Staring

James Staring is a personal trainer based in Clapham, London. His methods have featured in publications such as Your Fitness, Hello, Healthy, Daily Mail, Closer, and many more. After giving up smoking and entering the fitness industry in 2009, James has focused on his passion to help others transform their health and fitness. However, James is convinced most people struggle so much more than they need to in an effort to improve their fitness. Through his company, Fit to Last, James has helped hundreds of men and women make small adjustments in their daily habits to transform their fitness and to love how they look and feel.