In 16 states, at least 35% of residents reported having obesity last year, up from nine states in 2018 and 12 in 2019, according to data released Wednesday by the CDC.

Obesity increases the risk of being hospitalized and dying of COVID-19 and is linked to many other serious health conditions including diabetes, heart disease, and some cancers.

Delaware, Ohio, Iowa, and Texas joined Alabama, Arkansas, Indiana, Kansas, Kentucky, Louisiana, Michigan, Mississippi, Oklahoma, South Carolina, Tennessee, and West Virginia as states with the highest prevalence of obesity.

Pennsylvania’s overall rate remained unchanged, with at least 30% of surveyed adults reporting obesity, but racial disparities also continued. The prevalence of obesity among Black residents was at least 40% last year, the same as in 2019. The CDC had insufficient data to calculate rates for New Jersey.

Obesity is defined as a body mass index of 30 or greater (175 to 190 pounds for a 5-foot, 4-inch woman). While experts acknowledge the BMI formula is imperfect — for example, it doesn’t consider the location of the fat — it is a well-studied indicator of health risks.

“To change the current course of obesity will take a sustained, comprehensive effort from all parts of society,” the CDC said in a statement. “We will need to acknowledge existing health disparities and health inequities and address the social determinants of health such as poverty and lack of health care access.”

Obesity disrupts normal immune response in ways that researchers are still unraveling, and experts initially wondered whether COVID-19 vaccines would adequately protect people with obesity. But data on the vaccines authorized in the U.S. — by Pfizer-BioNTech, Moderna, and Johnson & Johnson — show effectiveness is not significantly different between people with and without obesity, according to a review by the Obesity Society published in July in the journal Obesity.

» READ MORE: America’s obesity epidemic threatens effectiveness of any COVID-19 vaccine

Although vaccination rates among people with obesity are not being tracked, five states with the highest obesity rates are among those with the lowest vaccination rates -- Alabama, Arkansas, Louisiana, Mississippi, and Tennessee. Residents of these low-vaccination states are four times more likely to be hospitalized and five times more likely to die of COVID-19 than residents in the 10 states with the highest vaccination rates, according to a CNN analysis of federal data.