NHANES is an ongoing initiative conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention to collect information on the health and nutritional status of a nationally represented cross-sectional sample of the total civilian, noninstitutionalized US population. The NHANES design is a stratified, multistage probability sample based on selection of counties, blocks, households, and the number of people within households. In 1999, the survey became a continuous program with a changing focus on a variety of pertinent health and nutrition measurements . The methods and study design for NHANES have been previously described [18, 19]. Data from 24-hour dietary recalls were collected using the Automated Multiple-Pass Method (AMPM) . The Day 1 interview was conducted in person in a Mobile Examination Center (MEC) and was used for this study.
Energy and nutrient intakes were calculated using the United States Department of Agriculture (USDA) Food and Nutrient Database for Dietary Studies (FNDDS) versions 1.0  2.0  and 3.0 . NHANES uses the FNDDS to process and analyze dietary recall data. These databases have been previously described .
We used the MyPyramid Equivalents Database (MPED) versions 1.0  and 2.0  to examine consumption in terms of MyPyramid now called MyPlate  servings (hand matching foods without values in more recent NHANES surveys). The MPED translates dietary recall data into equivalent servings of the seven MyPlate major food groups and corresponding subgroups. The number of MyPlate servings was based on the 24-hr food dietary recall data from NHANES 2001–2008 participants. Avocado consumers were identified as NHANES 2001–2008 participants who reported eating any amount of avocado during the 24-hour dietary recall.
Diet quality was calculated using the USDA’s Healthy Eating Index (HEI)-2005 [28–30]. The HEI-2005 is a measure of diet quality that indicates how closely diets adhere to the 2005 Dietary Guidelines for Americans, and is primarily used by the USDA to monitor the diet quality of the US population. The original HEI was created in 1995 and revised in 2006 to reflect the 2005 Dietary Guidelines for Americans. Food group standards  and the development and evaluation of the HEI-2005 have been previously described [32, 33].
Health indices evaluated included body weight, body mass index (BMI), waist circumference, HDL cholesterol (HDL-C), and risk of metabolic syndrome. The latter was defined as the presence of three or more of the following components: waist circumference ≥ 40 in (102 cm) for males or ≥ 35 in (88 cm) for females; triglycerides ≥ 150 mg/dL; HDL-C <40 mg/dL for males and < 50 mg/dL for females; blood pressure ≥ 130/85 mm Hg; or fasting glucose ≥ 100 mg/dL .
Least square means, standard errors of the mean, and ANOVA were determined for avocado consumption, diet quality, energy and nutrient intakes, and physiological markers of metabolic disease risk (ie, body weight, BMI, waist circumference, and HDL-C) in avocado consumers and non-consumers. The results were weighted using the NHANES examination sample weights to produce national estimates and adjust for the complex sample design of NHANES. Diet quality and food group/nutrient intakes were adjusted for age, gender, ethnicity, poverty income ratio, self-reported physical activity level, smoking status, alcohol intake, and energy intake. Physiological variables were adjusted for age, gender, ethnicity, poverty income ratio, self-reported physical activity level, smoking status, alcohol intake and BMI (for non-weight related variables). Minimal statistical significance was set at p < 0.05. Data were analyzed with the statistical packages SAS version 9.2 (SAS Institute, Cary, NC) and SUDAAN version 10.0.1 (2009, RTI, Research Triangle Park, NC).