The number adhering to all five "healthy habits" has fallen
The number of US adults following a healthy lifestyle has fallen in the last two decades despite increasing public health campaigns, a study shows.
A review of two studies stretching back to 1988 found the proportion of obese adults has crept up to over a third.
Levels of exercise also fell, as did consumption of fruit and vegetables.
The American Journal of Medicine study found those with health problems were no more likely to follow a healthy lifestyle than their fitter peers.
Researchers at the Medical University of South Carolina compared two large-scale studies covering the period 1988 to 2006.
During those 18 years, the percentage of adults aged 40-74 years with a body mass index (BMI) greater than 30 rose from 28% to 36%.
The number of people exercising three times a week or more fell from 53% to 43%, while the number of people eating five portions of fruit and vegetables a day fell by nearly 40%.
At the same time, smoking levels remained the same and moderate drinking slightly increased.
Overall, researchers found, the number of people adhering to all five "healthy habits" - including maintaining a healthy weight and stopping smoking - decreased from 15% to 8%.
This drop "demonstrates that the amount of emphasis by the current health system on prevention and healthy lifestyles may be insufficient," wrote lead author Dana King.
"The implications of the decreasing rates of healthy lifestyle habits include the possibility of an upswing in cardiovascular morbidity and mortality, and increase in the number of aging persons with disability and decreased quality of life due to the burden of chronic disease."
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But he added that research showed individuals could be persuaded to adopt healthy behaviour in middle age, and more effort should be focused on this.
Dr Steven Galson, the acting US surgeon general, said: "There is clearly a lot of work that needs to be done.
"If we want all Americans to achieve the health benefits of a healthy lifestyle, then all members of society must take action including parents, educators, community leaders, government as well as the individual.
"Together we can help Americans understand the severity of obesity, the efforts being made to address it, and how to maintain a healthy weight and live a healthy lifestyle."
Professor Alan Maryon-Davis, president of the UK Faculty of Public Health commented: "This is a wake-up call for the UK. What happens in America often happens over here a few years later."