How Much Should I Weigh?
The first thing to say is that you are unique. You are growing and developing, and your weight is going to vary according to these four factors: age; gender; height and build. And within those variables there is a range, rather than an exact weight that determines whether you are in the healthy weight category.
The BMI (body mass index) is the measure used to determine healthy weight, and is calculated by taking your weight (in kilograms) and dividing it by your height squared (in metres). So if you are 55kg and 1.6 metres tall you can work out your BMI on your phone or calculator by 55 ÷ 1.6 ÷ 1.6 = 21.48.
If your BMI is:
Below the 2nd centile you are in the underweight category.
Between the 3rd and 90th centile you are in the healthy weight category.
Between the 91st and 98th centile you are in the overweight category.
Above the 98th centile is in the very overweight or clinically obese category.
Above the 99.6th centile is severely obese.
So if you’re a 13-year-old girl with the above measurements giving a BMI of 21.48, you’re in the 81st centile, and if you’re a 13-year-old boy you’re in the 89th centile, which is in the healthy weight range for your age, gender and height.
But (and there’s a big but), any system that tells people whether they are ‘normal’, ‘underweight’, ‘overweight’ or ‘obese’ is bound to be controversial, and the limitations of BMI are that it doesn't distinguish between fat and muscle, and it doesn’t take into account build.
For example, we’ve all heard about rugby players coming up as obese and many athletes having a BMI that takes them into the overweight or very overweight category because muscle is more dense than fat.
And this limitation also applies to children and young people. You might find yourself in the ‘overweight’ or ‘very overweight’ category when you feel that you’re a healthy weight, so bear this in mind if you’re very athletic and sporty (so probably have more muscle on your body than others of similar height).
Remember, your weight is unique to you and your body will continue growing and developing until your late teens and even twenties.
Don’t be tempted to compare yourself to others – especially so-called ‘Instagram sensations’. Today's media promotes super thin, tall models, many of whom are underweight. Comparing yourself to them promotes unrealistic expectations of yourself and can contribute to developing eating disorders like bulimia and anorexia nervosa, which are detrimental to good health and can even be fatal.
And finally, never go on a diet. Diets are temporary food restrictions with the goal of weight-loss. However as soon as you start eating normally again, the weight goes straight back on! It’s a pointless exercise. You don’t need to diet. Why? Because you’re growing, so as long as you maintain your weight, as you grow taller you will achieve a healthy weight.
So focus on eating as nutritious a diet as possible – lots of fruits and vegetables, wholegrains, and protein foods like fish, meat, chicken, beans, chick peas, lentils, eggs, cheese and nuts. And not too much sugar and junk food. And stay active and fit. If you do this, as you grow, you’ll be healthy, fit, full of energy, and you will achieve a healthy weight.