According to dietitian Sue Baic, the median weight for an adult British man is 70 kilos, and for a British woman 60 kilos. These figures are almost certainly now out of date, and the figures will be higher.
The folliowing figures come from the Health Survery for England 1995. From measurements of height and weight, informants' Body Mass Index (BMI) was calculated as their weight in kilograms divided by the square of their height in metres. Among those aged 16-64, mean BMI was 26.0 kg/m2 in men and 25.6 kg/m2 in women.
There were significant differences in mean BMI (adjusted for age) between social classes. For both men and women, BMI, and also the prevalence of obesity, tended to be higher in manual classes (IIIM, IV, V) than in non-manual classes (I, II, IIINM).