Exploring The Relationship Between Body Mass Index and Body Fat Percentage Across Age and Gender: A Cross – Sectional Study

Abstract

Background: In today’s fast-paced world, the prevalence of non- communicable diseases (NCDs) is rising due to work, academic and personal pressures. Obesity, a preventable disease, is often underestimated in clinical settings. The ‘obesity paradox’ where NCDs occur in individuals with normal body mass index (BMI), complicates health assessments. This study evaluates the relationship between BMI and body fat percentage (BFP) by age and gender and assesses if BMI alone is a good predictor of body adiposity. Methods: A cross-sectional observational study was conducted on 385 normal healthy subjects aged 18-67 years, attending an annual temple festival in Kerala during 2016. Subjects were selected based on the inclusion and exclusion criteria, after obtaining the ethical clearance. Using an Omron Body fat analyser, we measured BFP. Statistical analysis was done using Independent T test, ANOVA and Chi square test on SPSS version 20. Results: A significant increase in BMI and BFP with age in both genders, with BFP changes starting at a younger age. Females showed higher increases in both BMI and BFP. Among participants, 34% had normal BMI. 29% had normal BFP and only 20% had both normal. We also found many ‘invisible’ obese individuals within the normal BMI group and some ‘muscle obese’ individuals in the overweight BMI group.  Conclusions: To conclude, as BMI and BFP increase with age, the quality of fat free mass likely deteriorates. BFP is a better predictor of adiposity compared to BMI. For early NCD detection, both BMI and BFP should be included in routine clinical screenings.