Conventional anthropometric measures used to predict dyslipidemia, such as body mass index and waist circumference, vary over time and may not fully capture early-life influences on metabolic risk. Fixed skeletal proportions, including limb length ratios, remain stable after physical maturity and may reflect developmental exposures relevant to lipid metabolism. This study examined the association between the upper arm-to-upper leg length ratio (UA/UL), a fixed skeletal proportion metric with established links to diabetes risk and dyslipidemia; this represents an application not previously reported in a nationally representative U.S. population. We conducted a cross-sectional analysis of adults aged ≥20 years using data from the National Health and Nutrition Examination Survey (NHANES) 2017-March 2020 (n = 7569). The UA/UL ratio was calculated from standardized upper arm and upper leg length measurements and categorized into quartiles based on the weighted sample distribution. Dyslipidemia was defined according to National Cholesterol Education Program Adult Treatment Panel III criteria or current lipid-lowering medication use. Survey-weighted logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) across progressively adjusted models. Dyslipidemia prevalence increased across UA/UL quartiles (58.4% in Q1 to 81.3% in Q4; p < 0.001). In unadjusted analyses, individuals in the highest UA/UL quartile had greater odds of dyslipidemia compared with the lowest quartile (OR 3.10, 95% CI 2.49-3.86). Associations remained significant after adjustment for demographic factors and for anthropometric measures considered separately. However, the association was attenuated and no longer statistically significant in fully adjusted models that included demographics, adiposity measures, hypertension, and diabetes. In sex-stratified analyses, the association was attenuated and no longer statistically significant in either sex after full adjustment; formal interaction testing confirmed no significant effect modification by sex (p-for-interaction = 0.943).