Overweight is defined as a body mass index above 25 but below 30. For a man of 5ft 9in, that is between 12 stone 4lb and 14 stone 6lb, or for a woman of 5ft 6in, it is between 11 stone 3 lb and 13 stone 4lb. Ideal, healthy weight is defined as a BMI between 18.5 and 25.