From the CDC:
Results: Overall self-reported obesity prevalence in the United States was 26.7%. Non-Hispanic blacks (36.8%), Hispanics (30.7%), those who did not graduate from high school (32.9%), and persons aged 50–59 years (31.1%) and 60–69 years (30.9%) were disproportionally affected. By state, obesity prevalence ranged from 18.6% in Colorado to 34.4% in Mississippi; only Colorado and the District of Columbia (19.7%) had prevalences of <20%; nine states had prevalences of ≥30%.
DC the least obese? Especially given the high percentage of African American population? The NY Times writes:
Dr. Dietz said the relatively low prevalence of obesity in Washington was harder to explain, particularly because the area has a large black population.
He said one explanation may be that many residents ride the subway; studies have shown that compared with people who drive, those who use public transportation tend to be thinner because it involves more walking. In addition, Dr. Dietz said, there is evidence of above-average fruit and vegetable consumption, and higher rates of breast-feeding, both of which are linked to lower rates of obesity.