With exception of people who have an underactive thyroid gland, being overweight is not a consequence of having a slow metabolism. The key factor in your metabolism is body weight and the heavier you are, the more the body has to work, the faster your metabolic rate will be and the more calories required.
Someone who weighs 15 stone and is 5'6" will have a much faster metabolic rate than someone of nine stone and the same height. If the heavier person loses weight and reduces their weight to nine stone their metabolic rate will slow down and will be similar to the first individual.
