Healthy weight is now defined according to the body mass index (BMI), which is calculated as a ratio of weight to height by taking your weight in kilograms and dividing it by the square of your height in meters.  For example, if your height is 1.8 meters, the divisor of the calculation will be (1.8 * 1.8) = 3.24. 

If your weight is 70 kilograms, then your BMI is 21.6 (70 / 3.24).

This method together with the body shape provide a good indication of a persons health as being overweight may result in diabetes and or cardiovascular diseases. If your BMI is more than 25 it is recommended that you start a weight control program and if your BMI is 30 + you are considered obese. It must however be noted that BMI may overestimate body fat in very muscular people as muscle weight more than fat. 

Now when you know your BMI it is good to know your Basal metabolic rate BMR, which is how many calories your body needs just to be functioning and based on your current activity level you can estimate how many calories you should consume in order to loose weight.

For men:

BMR [kcal/24 h] = 66,47 + 13,7 × weight [kg] + 5 × size [cm] − 6,8 × age [years]

For women:

BMR [kcal/24 h] = 655,1 + 9,6 × weight [kg] + 1,8 × size [cm] − 4,7 × age [years]

Men and woman store fat in different areas of the body and for men this is mostly in the upper arms, shoulders and abdomen where as for woman it is mainly in the breast, hips, buttocks and tights. Measuring your waist will give you a good indication weather you are carrying excess weight. A waist circumference above 94 cm (37in) in men and 80cm (32in) in women indicate hat you are carrying excess weight around the middle which may increase your chances for developing high blood pressure, raised cholesterol levels, diabetes and cardiovascular diseases. Men with a waist measurement of 102cm (40in) and woman of 88cm (35in) puts you in a high risk.

People who tend to gain weight mainly around their waist are said to have a apple shape and people who tend to gain weight around the hips, buttocks and tights are said to have a pear shape. The location of your fat affects your health but you can do nothing to change weather being apple or pear shape it is an inherited characteristic, but you can however limit its extent by controlling your weight and keeping fit.