It seems that both numbers are from the same report. Here's an excerpt from the report:
> How is it that only 12 states have adult obesity rates exceeding 35 percent, yet the national obesity rate is 42.4 percent? It’s because state obesity rates are from the BRFSS, which collects self-reported height and weight. Research has demonstrated that people tend to overestimate their height and underestimate their weight. In fact, one study found that, due to this phenomenon, the BRFSS may underestimate obesity rates by nearly 10 percent. NHANES, from which the national obesity rate is derived, calculates its obesity rate based on measurements obtained at respondents’ physical examinations. Accordingly, the higher rates found by NHANES are a more accurate reflection of obesity in the United States.
> How is it that only 12 states have adult obesity rates exceeding 35 percent, yet the national obesity rate is 42.4 percent? It’s because state obesity rates are from the BRFSS, which collects self-reported height and weight. Research has demonstrated that people tend to overestimate their height and underestimate their weight. In fact, one study found that, due to this phenomenon, the BRFSS may underestimate obesity rates by nearly 10 percent. NHANES, from which the national obesity rate is derived, calculates its obesity rate based on measurements obtained at respondents’ physical examinations. Accordingly, the higher rates found by NHANES are a more accurate reflection of obesity in the United States.
https://www.tfah.org/wp-content/uploads/2020/09/TFAHObesityR...