The Trust for America's Health (TFAH) and the Robert Wood Johnson Foundation found adult obesity rates rose in 23 of the 50 states, but fell in none.
In addition, the percentage of obese and overweight children is at or above 30% in 30 states.
The report warns widespread obesity is fuelling rates of chronic disease, and is responsible for a large, and growing chunk of domestic healthcare costs.
Obesity is linked to a range of health problems, including heart disease, stroke and type 2 diabetes.
Dr Jeff Levi, TFAH executive director, said: "Our health care costs have grown along with our waist lines. "The obesity epidemic is a big contributor to the skyrocketing health care costs in the US.
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