Introduction: The health risks associated with increasing BMI are continuous and interpretation of BMI grading in relation to risk may differ for different ethnic groups. There is a need for developing different BMI cut-off points for different ethnic groups due to the increasing evidence that the association between BMI, percentage of body fat and body fat distribution differ across populations and therefore, the health risks increases below the cut-off point of 25 kg/m² that defines overweight in the current WHO classification. Objective: To standardize the BMI criterion for the population of Mumbai, BMI variation in different age groups and correlation of BMI variation & co morbidities. Subjects: The study included apparently healthy 1000 individuals, 500 males and 500 females in the age group of 20-70 years. Terminally ill, pregnant females, mentally and physically challenged individuals were excluded. Procedure: The subjects were chosen according to the inclusion and exclusion criteria. Their weight and height were measured, and BMI was calculated. Their medical condition was documented. Sex-specific receiver operating curve was used to assess the sensitivity and specificity of BMI cut off. Results: In the age group of 20 – 40 years, 4.3% of the individuals have increased BMI related medical problems whereas in the age group of 41 – 70 years, it is 19.6%. The incidence is significantly high in the people with age 41 and above. The BMI cut off for both the sexes in the age group of 20 – 70 years is 24 kg/m² (specificity = 81.1%, sensitivity =72%). The BMI cut off for the females is 25kg/m² (specificity = 80%, sensitivity = 80% ) and 24kg/m² for the males (specificity = 77.9% ,sensitivity= 73%).The BMI cut off for both the sexes in the age group of 20 – 40 years is 25 kg/m²(specificity = 72.2% ,sensitivity = 76% ). The BMI cut off for the females is 25 kg/m² (specificity = 100%, sensitivity = 69.5%) and same for the males (specificity = 61.5%, sensitivity = 82.5%).The BMI cut off for both the sexes in the age group of 41- 70 years is 24 kg/m² (specificity = 82.5%, sensitivity = 76.6%), the BMI cut off for females is 24kg/m²(specificity = 82%, sensitivity = 84.9% ) and same for the males (specificity = 81.3%, sensitivity = 75.3%). Conclusion: For the population of Mumbai, the BMI cut off for both the sexes in the age group of 20 – 70 years is 24 kg/m², 25kg/m² for females and 24kg/m² for males. The BMI cut off varies in different age groups. The BMI cut off for both the sexes in the age group of 20 – 40 years is 25 kg/m² (25 kg/m² for females and 25kg/m² for males). The BMI cut off for both the sexes in the age group of 41- 70 years is 24 kg/m² (24kg/m² for females and 24kg/m² for males). A direct correlation of BMI variation and co morbidities is found.

Keywords: Body mass index; Mumbai population, Obesity.