About two-thirds of U.S. adults are either overweight or obese, new figures suggest.

It's estimated 39.9 per cent of men (36.3 million) and 29.7 per cent of women (almost 28.9 million) were overweight and 35 per cent of men (31.8 million) and 36.84 per cent of women (nearly 35.8 million) were obese, researchers said in a letter published in Monday's issue of JAMA Internal Medicine.

State governments are trying to find ways to encourage people to be more physically active. (Brennan Linsley/Associated Press)

The study was based on sample data from the National Health and Nutrition Examination Survey or NHANES from 2007 to 2012 of 15,208 adults 25 years of age of older who had their heights and weights measured, a sample the researchers said was representative of more than 188 million people.

"Compared with 1988-1994, the distribution of the population's weight status has increased in the past 20 years," Dr. Graham Colditz and Lin Yang of the Washington University School of Medicine in St. Louis said.

To counter the burden of obesity both now and on future generations, the researchers said it's a priority to deliver population-wide strategies to reduce risk factors.

They suggest changes to the physical environment, enhancing efforts by family doctors to prevent and treat obesity and altering societal norms.

In January, the Canadian Task Force on Preventive Health Care released its recommendations on prevention of weight gain and treatment of overweight and obesity.

The first step is for doctors to measure heights, weights and calculate body mass index at primary care visit to monitor weight changes since people often don't realize it's happening.

Obesity measurements among adult Canadians almost doubled from 14 per cent in 1978-1979 to 26 per cent in 2009-2011.