Background and objective: The United States has experienced a large increase in the prevalence of obesity since the 1970s. Our objective was to describe recent trends in obesity and abdominal obesity among adults in the United States.

Design: Trend study of cross-sectional studies.

Subjects: We used data from up to 22,872 men and non-pregnant women aged ≥ 20 years from the National Health and Nutrition Examination Survey (NHANES) 1999-2008.

Main outcome measures: Main outcome measures are mean body mass index and waist circumference, percentages of obesity and abdominal obesity. Obesity was defined as a body mass index ≥ 30 kg m(-2), and abdominal obesity was defined as a waist circumference ≥ 102 cm in men and ≥ 88 cm in women.

Results: In men, the age-adjusted mean body mass index, mean waist circumference, and prevalence of obesity and abdominal obesity were 27.8 kg m(-2), 99.1 cm, and 26.9 and 37.8%, respectively, during 1999-2000 and 28.5 kg m(-2) (P (trend) = 0.001), 100.8 cm (P (trend) = 0.002), and 32.0 (P (trend) = 0.001) and 43.7% (P (trend) = 0.002), respectively, during 2007-2008. In women, the age-adjusted mean body mass index, mean waist circumference, and prevalence of obesity and abdominal obesity were 28.2 kg m(-2), 92.2 cm, and 33.2 and 55.8%, respectively, during 1999-2000 and 28.6 kg m(-2) (P (trend) = 0.181), 94.9 cm (P (trend) = 0.006), and 35.2 (P (trend) = 0.180) and 61.8% (P (trend) = 0.036), respectively, during 2007-2008. Significant linear trends for increasing prevalence of obesity were noted among men with the least and most education.

Conclusion: Between 1999 and 2008, both obesity and abdominal obesity increased in men, and abdominal obesity increased in women.