Introduction: Blood group is a classification of blood, based on the presence or absence of surface antigenic substance on the red blood cells. ABO blood group system is widely known and studied for its relation with various diseases and their complications. The idea of correlating diseases with blood groups started with the observation that certain diseases are common in persons with common racial and ethnic origin. For example, Arid et al ^[1] found that peptic ulcer is to predominate in blood group O and that gastric carcinoma is found more frequent in blood group A.

Obesity is defined by World Health Organization (WHO) as abnormal and excessive fat accumulation ^[2]. Obesity is an important risk factor for many non-communicable diseases such as metabolic syndrome, type 2 diabetes, cardiovascular diseases and cancer ^[3-5]. The prevalence of overweight and obesity in most developed and developing countries have been increasing markedly ^[6] over the few years. Obesity has been linked to more deaths than the underweight population ^[7].

Body Mass Index (BMI) is a good measure of general adiposity ^[8]. The proposed classification based on BMI is: underweight with BMI <18.5, 18.5-24.9 is normal BMI range, 25-29.9 are preobese, 30-34.9 are classified as obese class I, 35-39.9 obese class II and >40 are obese class III. Body mass index being a modifiable risk factor can be assessed in time and blood groups being non modifiable risk factor should be identified as being prone to developing obesity, so that population can be accordingly counseled for the life style modifications and thus be prevented from major diseases associated with increased BMI ^[5].

Hence this study was planned with an attempt to explore relationship between blood group antigens and BMI to predict the type of population which is more prone to be obese and hence at risk of many associated diseases, which can be modified by simple modification of lifestyle. And education of the community for the primary prevention in ‘at risk’ blood group to reduce emergence of the disease in the population.

Method: The present study was a prospective, cross sectional, single centric, open labeled, observational study conducted in the Department of Physiology in collaboration with blood bank in Tertiary care hospital. Before commencement of the project, approval was taken from the Institutional Ethical Committee. The data collection was done between December 2016 to August 2018 and data was analysed between September 2018 to November 2018. The study design involved 500 individuals who were the voluntary healthy blood donors (both male and female) participating in blood donation camp. Subjects were briefed about the rationale of the study and were assured that information provided by them — including name, identity and data — would not be disclosed at any time ^[9].

Written informed consent was taken after explaining to the subject about the study in English / Hindi / Marathi, language which they can understand. This study was carried out within the acceptable ethical norms ^[10].

Relevant information including name, age, sex, occupation, place of residence, medical history was documented and clinical examination of the subjects was carried out following a pre-designed proforma ^[9]. Donors were deferred or accepted according to their medical history regarding chronic or acute diseases ^[5].

It was followed by physical examination of the donor. Blood was taken from a donor only after fulfilling all the eligibility criteria of a healthy donor and healthy clinical parameters.

Observation: As observed, maximum number of people belonged to preobese category, which was predominated by the age group of 18 - 30 years. While analysis of obesity cadre gave a result as those belonging to 31 - 40 years of age group were the main population (50%) contributing to obese people than the major group of 18 - 30 years which predominated normal and preobese population.