The physical activity level of an individual can be determined by assigning physical activity ratios (PAR) to different activities. The PAR is the ratio of the energy expended in a particular activity and the BMR, and is thought to be independent of body weight. PAR values of selected activities in Indian male and female subjects were measured and their association with BMI was assessed. The BMR and energy cost of selected activities were measured in thirty male and thirty female subjects in the age group of 20–40 years, who were categorised into different groups of BMI. The PAR values of the underweight male subjects were significantly lower than the overweight subjects for activities such as walking at 3·2 and 4·8km/h and walking at 3·2km/h with a 5kg load. In the female subjects, the underweight subjects had significantly lower PAR values for floor swabbing, and walking at 3·2 and 4·8km/h when compared with overweight females. The mean data of the male and female subjects of the present study were slightly but significantly different to the previously reported FAO, WHO and United Nations University values and other compilations. The BMI was significantly correlated with the PAR value of the studied activities. In India, where a large proportion of the population have BMI below 18·5 and above 25kg/m2, considerations of the influence of body weight and BMI on PAR become important in accurately determining total energy expenditure.