The "fit but fat" concept revisited: population-based estimates using NHANES

Table 2 Differences in major outcomes by body mass index level.

	Normal weight	Overweight	Obese
Age (mean years)	32.4 ± 0.8	34.4 ± 0.5	34.5 ± 0.9
Estimated VO_2max (mean ml.kg^-1.min^-1)	42.9 ± 0.4*	41.8 ± 0.9*	38.7 ± 0.6
Fitness Level (percentage) †§
Low	2.0 ± 0.5 (2,920,699)	4.3 ± 0.6 (6,188,369)	3.9 ± 0.5 (5,644,436)
Medium	12.9 ± 1.3 (18,451,215)	13.0 ± 1.1 (18,573,013)	7.6 ± 0.8 (10,819,591)
High	30.0 ± 2.3 (42,968,269)	17.4 ± 0.4 (24,868,929)	8.9 ± 1.0 (12,790,983)

Data presented as the mean or percent and standard error (SE). Symbols for statistical significance: * = different from obese at p < 0.05; † = distribution of fitness level different across body mass index (BMI) groups. §The nine cells for fitness level by BMI level sum to 100% and represent the distribution across the population. The weighted sample size for each cell is indicated in parenthesis for the total analytic sample N = 143,225,503. Fitness level was categorized using sex and age-specific criteria for adults 20-49 yr. from the Aerobics Center Longitudinal Study, where low was defined as an estimated VO₂max below the 20^th percentile of the same sex and age group, moderate between the 20^th and 59^th percentiles, and high at or above the 60^th percentile. Cut-points used to define weight status by BMI (kg/m²) level are: normal weight < 25; overweight > 25 < 30; and, obese > 30.

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