Physical Fitness but Not Diet Quality Distinguishes Lean and Normal Weight Obese Adults.

BACKGROUND: Individuals with normal weight obesity (NWO) have increased cardiometabolic disease and mortality risk, but factors contributing to NWO development are unknown.
OBJECTIVE: The objective of this study was to determine whether diet quality scores and physical fitness levels differed between adults classified as lean, NWO, and overweight-obese. Secondary objectives of the study were to compare clinical biomarkers and food groups and macronutrient intakes between the three groups, and to test for associations between body composition components with diet quality scores and physical fitness levels.
DESIGN: This is a secondary data analysis from a cross-sectional study that included metropolitan university and health care system employees. Body composition was measured by dual energy x-ray absorptiometry. Individuals with a body mass index <25 kg/m2 and body fat >23% for men and >30% for women were classified as having NWO. Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension score, and Mediterranean Diet Score were calculated from Block food frequency questionnaires. Physical fitness was assessed by measuring maximal oxygen uptake (VO2 maximum) during treadmill testing. PARTICIPANTS/
SETTING: This study included 693 adults (65% women, mean age 48.9 ± 11.5 years) enrolled between 2007 and 2013 in Atlanta, GA. MAIN OUTCOME MEASURES: The main outcome measures were Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension, and Mediterranean Diet Score diet quality scores and maximal oxygen uptake. STATISTICAL ANALYSES: Multiple linear regression analyses with post hoc comparisons were used to investigate group differences in fitness, diet quality, and biomarkers. Regression analyses were also used to examine relationships between diet quality scores and fitness with body composition.
RESULTS: VO2 maximum was significantly lower in the NWO compared with the lean group (36.2 ± 0.8 mL/min/kg vs 40.2 ± 1.0 mL/min/kg; P < 0.05). Individuals with NWO reported similar diet quality to lean individuals and more favorable Alternate Healthy Eating Index and Dietary Approaches to Stop Hypertension scores than individuals with overweight-obesity (P < 0.05). Diet quality scores and physical fitness levels were inversely associated with percent body fat and visceral adipose tissue (P < 0.05), regardless of weight status. Individuals with NWO exhibited higher fasting blood insulin concentrations, insulin resistance, low-density lipoprotein cholesterol, and triglyceride levels, and significantly lower high-density lipoprotein cholesterol levels than lean individuals (P < 0.05).
CONCLUSIONS: Physical fitness was significantly decreased in individuals with NWO compared with lean individuals. Higher diet quality was associated with decreased total and visceral fat but did not distinguish individuals with NWO from lean individuals.