An Investigation into the Prevalence of Normal- Weight Obesity in a Female Population Residing in Scotland.

Abstract

Introduction: Body Mass Index (BMI) is the accepted measure of diagnosing obesity in clinical practice however this method has many limitations, mainly BMI cannot distinguish between lean and fat mass which both contribute to weight but have opposite impacts on health. BMI miscategorises a significant amount of normal weight people as healthy when they are at the same health risks as someone with a BMI in the obese range, due to high body fat percentage - individuals exhibiting these characteristics are diagnosed as Normal-Weight Obese. Prevalence has ranged from 5.4% to 36% in various populations. Hypothesis: Normal-Weight Obesity does exist in the young female student population at Queen Margaret University at an expected prevalence of approximately 10%. Methodology: A cross-sectional study of 18-25 year old female students at Queen Margaret University with normal BMI (18.5-25.0kg/m2). Anthropometric measurements (height, weight and waist circumference) were obtained by two trained researchers following strict protocol. Body composition was measured using Bioelectrical Impedance Analysis. Physical activity and diet was self-reported. Normal-Weight Obesity was defined as normal BMI and body fat >30%. Results: Forty seven females with a mean age of 21.06 (± 1.34) participated in the study in March 2017. Among 37 normal weight subjects, 16.2% (n = 6) were identified as Normal-Weight Obese. Normal-Weight Obese females tended to be significantly shorter and heavier and have significantly higher BMI and body fat percentage than lean counterparts. Body fat percentage was strongly correlated with BMI (r=0.84, p<0.001); physical activity was negatively correlated with body fat percentage in Normal-Weight Obesity (r=-0.91, p<0.05); frequency of weight-bearing activity inversely correlated with body fat percentage more strongly than duration. Consumption of macronutrients did not differ between groups nor correlate with body fat percentage (p>0.05). Conclusion: This was the first study to investigate Normal-Weight Obesity in Scotland; results were consistent with the majority of published studies in that Normal-Weight Obesity occurs in a moderate proportion of the normal weight population. A novel finding from these results is that frequency of weight-bearing activity may have greater impact on composition than duration. A more extensive sample is required to find significant results. KEY WORDS: Normal-Weight Obesity • Body fat percentage • Composition • Body Mass Index • Physical Activity