Body mass index is the ratio of a person's height to their weight. It is important for adults to consider this relationship when deciding if they are healthy or if steps need to be taken to live a more healthy lifestyle.
According to the NHS, a normal BMI for an adult is between 18.5 and 24.9. That means for a person who is 165 cm (5 foot 5 inches), a healthy weight is between 50 and 68 kg (7 stone 12 and 10 stone 10 pounds). Someone who is 183 cm (6 foot) should weigh between 63.5 and 83.5 kg (10 stone and 13 stone 2 pounds). BMI is a strong indicator of body fat, but it should not be used to solely determine good health.
Someone with a BMI of less than 18.5 is considered underweight. Someone who is 173 cm (5 foot 8 inches) should not weigh less than about 57 kg (9 stone). Some fat is necessary for energy production and to maintain a healthy lifestyle. Too little fat could lead to decreased bone mass and other problems.
Those who are considered overweight have a BMI between 25 to 29.9. Someone who is obese has a BMI higher than 30. An individual who is 170 cm (5 foot 7 inches), weighing more than 81 kg (12 stone 11 pounds) is considered overweight. A person who is 185 cm (6 foot 1 inch) and weighs more than 103 kg (16 stone 3 pounds) is considered obese on the BMI scale.