This week I was talking to a very well informed client who asked me for an explanation of BMI and body fat percentages.
It’s not the first time I’ve been asked so I thought I’d have a bit of a focus on these elusive numbers, plus introduce you to a few other important figures in your quest for better health. We’re going to look at BMI, Body Fat, Blood Pressure, Waist to Hip Ratio and Vo2max.
If your plan is to make health changes, these measurements give you simple and useful gauges to keep you on track. If all of these figures are in the safe and/or normal ranges, you can be confident that you’re the proud owner of a fit and healthy bod.
1. Body Mass Index
BMI is an exact figure found by dividing your weight in Kg by your height in m². For the mathematically challenged among us, you can find your exact BMI by following this link.
A safe BMI is deemed to be anything between 18-25 although a fit and powerful person may easily fall into the overweight 25-30 category and still be healthy. Much is written about the invalidity of BMI as it only takes into account weight and height without considering body type or muscle mass. This may be true of a rugby scrum half but it’s unlikely to be a get out clause for the average office worker. If you’d like to see what different BMI’s look like, check this BMI visualiser. It’ll show you roughly what our bodies look like at different BMI levels.
2. Body Fat
This is the amount of fat stored in our body, including dangerous, organ smothering, visceral fat. Body fat percentages seem similar to BMI for example, an athletic body fat percentage for women is 18-25%, although anything up to 30% is classed as normal, safe and healthy. A BMI of between 25-30 on the other hand is classed as overweight. For men, an athletic body fat amount is 6-18% with up to 25% still deemed safe and healthy. A man with body fat of 8% would be classed as healthy but a BMI of 8 is extremely underweight. Confusing, right? Here’s a little ready reckoner which might help.
Body fat is difficult to measure. Some weighing scales have a body fat measuring device built in but they’re not always accurate. In one day while trialling 2 different machines I measured 16% and 25% body fat. Another method is the use of callipers which pinch the skin to measure the fat. Accurate readings are hard to reproduce and you’ll need a friend to help. Hospitals have special pods which can read these amounts extremely accurately but the NHS may have more important uses for them than to let us all go for a fat measuring field trip.
The US Navy developed a fairly simple and repeatable body fat measurement system which is as good as any. It's done by comparing the size of your neck to your waist and hips. Here’s a link to a great description of it so you can try it at home:
3. Blood Pressure
We’ve probably all had our blood pressure taken at some point. Normal is deemed to be around 120/80, low is below 90/60, high is above 140/90. You can buy accurate blood pressure monitors for home use but it’s such a great indicator of good health that your local Nurse will most likely be happy to take it if you’re concerned. Most Personal Trainers will also have a blood pressure monitor and can give you a reading as a starting point. When your blood pressure is high there is potential constriction or strain on the walls of the arteries carrying oxygenated blood. Blockage or rupture is the cause of heart attacks and strokes so it’s an important figure to know, understand and manage. If you have been diagnosed with high blood pressure, taking your recommended medication is vital to good health. Order any repeat prescriptions in good time and count your meds before you go on holiday to make sure you don't run out. Always tell a trainer or fitness instructor if you have been diagnosed with high blood pressure. As long as it's medicated and stable you'll still be able to exercise.
4. Waist to hip ratio
Have you heard of Apple and Pear shapes? An apple shape will have slender legs and a rounded tummy, a pear will have a slimmer waist with extra fat stores around the hips and thighs. Those of us with pear shapes are known to experience less heart disease, the supposition being that this is because we don’t store our fat around our vital organs like round-tummied apples.
This provides another easy measurement for good heart health. Measure your waist and your hips in cms then divide the waist measurement by the hip measurement. For example, a woman with a waist of 70 cms and hips of 100 cms would be 70/100 = 0 .7. The World Health Organisation (WHO) states that abdominal obesity is defined as a waist/hip ratio above 0.90 for men and above 0.85 for women. People with a waist/hip ratio greater than these will have a higher risk of heart disease. While body shape is to some extent genetic we can reduce this risk by maintaining a safe BMI and body fat percentage.
5. Vo2 max
This is a measure of how much oxygen our muscles can transport and utilise during exercise. An exact measurement is dependent on a very tiring test where our oxygen levels are monitored using a mask, so not too easy to replicate at home. Personal Trainers should be able to perform fairly accurate Vo2 max tests with tests like the “Chester Step test” and there are loads of machines in gyms with built in software which will also give us a ball park figure. Both PT’s and gym cardio machines are accurate enough to record progressions over a 4-6 week set of periodised training (that’s a gym program to you and me!). The higher your Vo2max number, the healthier your heart is, the longer you’ll be expected to live and the greater your overall quality of life is expected to be. That means less medical intervention, less medication, less pain, more fun. If you have a gym membership, ask the duty trainer to show you how to find out your Vo2max. You can then use an interval training program on the same machine to build up your cardiovascular fitness and improve your Vo2 max reading over time. Expect to puff and pant a lot.
Okay – how did you measure up? Let’s not panic or try to change these numbers all at once. By working on one area, you’ll bring change to the others until eventually your health has improved and your overall readings are in the healthier categories. Hopefully this will lead to you feeling more energised and inspired to continue. Keep tuning into the blog for easy ways to make small changes to these results, your health and your life.
Enjoy Good Health!