The thinest states (by percentage not considered obese) are Colorado (84.0%), Hawaii (83.6%) and Massachusetts (83.2%).
The fattest (by percentage that are considered obese) are Indiana (26.0%), West Virginia (27.7%), Mississippi (28.1%) and Alabama (28.4%).
All states listed here.
Obese is defined having a body mass index (BMI) of 30.0 or higher. BMI is equal to your weight in pounds divided by your height in inches squared and then multiplied by 703. The Centers for Disease Control and Prevention has a BMI Calculator.