Normal-Weight Obesity and Body-Composition Profiles Among Pakistani Healthy Young Adults: A Cross-Sectional Study

Abstract

Background: Body mass index (BMI) is widely used to classify weight status but does not distinguish adipose from lean tissue. Normal-weight obesity (NWO) describes individuals whose BMI lies within the conventional normal range despite elevated body fat percentage (BF%).

Objective: To estimate the prevalence of NWO among normal-BMI healthy young adults, compare prevalence by sex, and examine selected body-composition characteristics of participants with NWO versus normal-weight non-obese (NWNO) participants.

Methods: This cross-sectional study included 96 healthy young adults aged 18-25 years from a public-sector medical college in Islamabad, Pakistan. Anthropometry and body composition were assessed using an eight-electrode segmental bioelectrical impedance analysis (BIA) device (Run Star FG2001). NWO was operationally defined as BMI 18.5-24.9 kg/m² together with BF% ≥25% in males or ≥32% in females. Prevalence was estimated among normal-BMI participants with Wilson 95% confidence intervals (CIs). Sex differences were assessed using Fisher's exact test and a crude prevalence ratio (PR). Primary body-composition comparisons were restricted to NWO and NWNO participants; selected associations were further evaluated with parsimonious regression adjustment for sex and BMI.

Results: Of 96 participants, 66 (68.8%) had BMI 18.5-24.9 kg/m²; 20 (20.8%) were underweight and 10 (10.4%) had BMI ≥25 kg/m². Among normal-BMI participants, 23/66 met the NWO definition (34.8%; 95% CI 24.5-46.9%). NWO was present in 22/42 normal-BMI females (52.4%) and 1/24 normal-BMI males (4.2%), corresponding to a crude PR of 12.57 (95% CI 1.81-87.51; Fisher's exact p<0.001). Compared with NWNO participants (n=43), NWO participants (n=23) had higher BF% and BIA-derived visceral-fat grade and lower skeletal-muscle percentage and BIA-estimated basal metabolic rate (BMR) in unadjusted analyses. After adjustment for sex and BMI, skeletal-muscle percentage was not independently associated with NWO (β=-1.13 percentage points, 95% CI -3.62 to 1.36; p=0.375), whereas BIA-estimated BMR remained lower (β=-108.5 kcal/day, 95% CI -157.7 to -59.4; p<0.001) and visceral-fat grade remained higher (β=1.68 units, 95% CI 0.54-2.82; p=0.004).

Conclusion: NWO was identified in approximately one-third of normal-BMI participants in this single-center sample and was markedly more frequent among females. Several large unadjusted body-composition differences were substantially attenuated after accounting for sex, while differences in BIA-estimated BMR and visceral-fat grade persisted. Larger representative studies using validated reference body-composition methods and cardiometabolic biomarkers are needed.