The Characterization of Normal Weight Obesity in College Students

Abstract

While normal weight obesity (NWO) has become an important health topic, to date no data exist describing physiological characteristics among this group. PURPOSE: The primary aim was to characterize NWO in college-age males and females through body composition and cardiometabolic measures. The secondary aim was to observe the relationship between waist to hip ratio (WHR) and body mass index (BMI) with body fat percentage (BF%). METHODS: Ninety-two college students (Mean ± SD; Age: 19.5 ± 1.4 yrs.; Height: 171.9 ± 9.4 cm; Weight: 67.9 ± 8.2 kg, BF%: 26.0 ± 6.2 %; males n=29; females n=63) participated in this study. NWO was defined being above NHANES body fat 25th percentile based on age and sex. Body composition variables including BF%, lean mass (LM), and visceral adipose tissue (VAT) were assessed by dual energy x-ray absorptiometry. The same technician measured waist and hip circumferences. Mean arterial pressure (MAP) and metabolic biomarkers [total cholesterol (TC), high density lipoproteins (HDL), non-high density lipoproteins (NHDL), and glucose (GLU)] were evaluated for cardiometabolic health. Blood pressure was measured in a seated position with an automated cuff; biomarkers were assessed by a fasted blood draw. RESULTS: Forty percent of the sample (n=37) was identified as NWO, with 31% of the females (n=19) being NWO, whereas 62% of males (n=18) were. NWO individuals had significantly higher BF% (28.4 ± 6.7% vs. 24.4 ± 5.2%, p<0.001), VAT (0.20 ± 0.15 kg vs. 0.07 ± 0.10 kg, p=0.002), and larger WHR (0.76 ± 0.40 cm 0.72 ± 0.41 cm, p=0.003) compared to normal weight lean (NWL). Although not significant, NWO had higher LM (46.2 ± 8.5 kg; NWL: 41.7± 10.3 kg, p>0.05) and MAP (NWO: 84.4 ± 6.8 mmHg; NWL: 82.5 ± 7.0 mmHg, p>0.05) compared to NWL. NWO also had higher levels of GLU, and lower levels of TC, HDL, and NHDL; however, biomarkers were not significantly different between groups (p>0.05). While WHR was significantly correlated with BF% (R= -0.293, p=0.005), BMI was not (p>0.05). CONCLUSION: The occurrence of NWO among otherwise healthy college students is high. Identification of these individuals may be an effective approach to obesity prevention and treatment. Determining effective methods to measure both body fat and abdominal obesity in this population is essential, as BMI may mask obesity in a young adult population.