If you're a number-crunchy fan and would like to calculate your BMI manually just follow these three steps. Work out your height in metres and multiply the figure by itself. It could be that you eat a varied and well-balanced diet but are naturally very slim. If so, there is no need to change what you eat, except perhaps to eat more food and make sure you are getting all the energy and nutrients you need to stay healthy. You should not try to lose any weight.
Weight loss offers no health benefits.
If you regularly make yourself sick, take laxatives or diuretics as a means of weight control, you should seek medical attention immediately. If you lose weight suddenly or for an unknown reason you should also see your doctor. You are in the healthy weight range and medical research suggests that this range is associated with the best health and least risk of heart disease, some cancers and osteoporosis. There are no health benefits to changing your weight. It is important that you eat a varied and well-balanced diet, and take regular physical activity that you enjoy to maintain a healthy weight throughout life.