A decline in the physical fitness of US children attributed to changes in modern life first caught the attention of President Dwight Eisenhower more than 50 years ago.
Studies culminating in a 1953 research paper by Dr Hans Kraus at New York University found US children less fit than European children, which President Eisenhower found "alarming."
Dr Kraus blamed an affluent 20th-century US lifestyle, with its significant cultural changes, including the use of cars, school buses and lifts instead of walking or climbing stairs, children confined to their neighbourhoods and fewer manual chores.
That led Mr Eisenhower in 1956 to establish the President's Council on Youth Fitness, which still exists today. Although no federal programme would be created for a "home and local community problem," he wrote, "more and better co-ordinated attention should be given to this most precious asset - our youth - within the federal government."
Now, at the beginning of a new century, social changes have led to even greater concern. Childhood obesity has tripled since 1980, to almost one in six; public health data has found a 40 per cent increase in overweight pre-schoolers aged two to five since 1994.
This is one of the wild cards in any US healthcare reform. Combined with an obesity rate of 30 per cent in adults, the problem of obesity and wellbeing in any healthcare reform could require a significant change in the federal government's spending priorities on prevention.
It could lead to increasing demands for people to take more personal responsibility to change unhealthy and costly lifestyles or risk paying more themselves.
Paul Mango, a healthcare expert at McKinsey, says: "If we do not arrest, and then reverse, the current rate of health-status deterioration, nearly all other initiatives to improve efficiency and effectiveness combined will not be sufficient to offset its effects."
The obesity epidemic could wreak havoc on future healthcare budgeting. They would get squeezed from both ends as the younger generation incurs more costs from chronic disease associated with obesity, such as diabetes, and costs continue to rise for the ageing baby boomers.
Several recent studies suggest that people engaging in unhealthy lifestyles consume nearly 50 to 75 per cent more health services per year. Other data show progress in reducing heart disease stagnating in young adults. A recent review of prescription data by Medco, the US drug benefits manager, showed children taking medicine for Type II diabetes - usually seen mostly in adults - also had a staggering increase in use of drugs for complications of diabetes, such as heart problems.
Jon Cohen, a healthcare expert for consultancy PwC, says: "There's no question that the obesity epidemic is the greatest threat to the American population."
To combat it, experts say a huge philosophical shift of economic incentives for health prevention is critical.
One way for this to occur would be a change in how Medicare, the healthcare programme for pensioners, reimburses doctors. There is currently little economic incentive for them to spend more time talking to patients about nutrition, fitness and health prevention.
A change in Medicare payments could trigger the private insurers to do more too, experts say. Other government interventions are appearing. A recent Senate proposal would ban the sale of junk food in school shops and vending machines. Efforts in Somerville, Massachusetts, called "Shape Up Somerville" helped reduce children's weight by a coordinated city-wide community effort led by health researchers.
Another shift in healthcare reform in light of the obesity epidemic could push more personal responsibility for costs arising from a person's lifestyle and health habits. Increasingly, consumers are being asked to take more financial risk and save money for that risk to try to make healthcare spending more efficient.
Employers have begun to ramp up efforts to change employees' lifestyles, from smoking to obesity, with incentives including lower health insurance payments for health changes.
