Doctors assess patients’ breathing, heart rate and blood pressure routinely at office visits. Soon, they may be adding body mass index (BMI) to that list.

Tracking this measure - an indicator of whether someone is obese or overweight - at medical checkups as if it were a vital sign is among a new set of strategies recommended for battling obesity, which some experts predict will affect 42 percent of adults by 2030.

Although professional medical societies have said for years that physicians should monitor patients’ body mass index, most doctors do not. A 2006 survey of family physicians found that fewer than half checked BMIs for children older than 2, even though 71 percent knew that such checks had been recommended.

Just over 40 percent of adult patients in commercial HMOs had documented BMI measurements in 2009 and 2010, according to a survey by the National Committee for Quality Assurance, an organization that evaluates health plans. That figure falls to 12 percent for patients in commercial PPOs, a more common type of plan.

The Institute of Medicine last week called for the medical profession and health insurers to become more rigorous in their approach. In a report, the group proposes a wide-ranging anti-obesity campaign that would involve individuals, families, schools, communities, workplaces, the food industry and the media.

For physicians, monitoring body mass index - a ratio of height to weight - is at the top of the list of priorities because it is the best way to identify people who have a weight problem. (Adults are counted as obese if they have a BMI of 30 or higher.)

“We need to normalize the process of obesity screening and lifestyle counseling so they’re usual and people expect this,” said Sandra Hassink, a member of the panel that prepared the institute’s report and director of the Obesity Initiative at Nemours, a pediatric health system in Florida, Delaware, New Jersey and Pennsylvania.

Several health-care systems have embraced regular BMI checks. Kaiser Permanente includes BMI as a “vital sign” in electronic medical records for nearly 9 million members, and it is planning to do the same for physical activity, said Ray Baxter, the health plan’s senior vice president for community benefit and health policy. (Kaiser Health News is not affiliated with Kaiser Permanente.)

So why the problem? Many physicians are unprepared to advise people about how to change their behaviors and unconvinced they have time to do so, and therefore they look skeptically at screening, said Robert Kushner, clinical director of the Comprehensive Center on Obesity at Northwestern University.

If doctors are overweight themselves, they are less likely to recognize the issue in their patients, research shows. What’s more, doctors are not trained in medical school to handle weight issues. They also often are not convinced that obesity treatments work, and many believe there are not good community programs to which they can refer patients.

“The question is, how many programs are out there for primary-care doctors to refer to in the community? And the answer is not many,” said Ned Calonge, a Colorado physician who is the immediate past chairman of the U.S. Preventive Services Task Force.

Another significant problem has been a historic lack of reimbursement from insurers for obesity screening and counseling. That changed last year for seniors, when Medicare said it would cover up to six months of weight loss counseling for obese beneficiaries as part of a package of new preventive services.

Meanwhile, new preventive-services guidelines from the government call for all insurance plans to cover obesity screening and counseling without charge to patients.

And insurers are expanding childhood obesity programs after a 2010 recommendation from the Preventive Services Task Force that endorsed comprehensive weight management programs for youngsters 6 or older. Previously, the task force supported BMI screening but not weight loss programs.

For the insurance industry, the challenge is providing evidence-based programs that can be introduced on a broad scale.

UnitedHealth Group is promoting Join for Me, a year-long behavioral modification program piloted with the YMCA of Greater Providence in Rhode Island, in which youngsters 6 to 17 years old, accompanied by a parent, learn about healthy eating and exercise in a group led by a coordinator.

WellPoint has taken a different approach, choosing to work through doctors and with the Alliance for a Healthier Generation, a Portland, Ore.-based organization that is trying to persuade health plans to offer more comprehensive coverage for obesity counseling and treatment. The alliance asks participating plans to offer four visits with a child’s primary-care doctor and four visits with a dietitian if the youngster is found to be overweight or obese. So far, several plans, including WellPoint, Aetna, Humana and Highmark, have signed up, and 2.4 million children are covered.

Insurance companies and some self-insured employers are also exploring the use of financial incentives - cash payments or reduced premiums or deductibles - to motivate members to keep their weight in check and adopt other lifestyle changes.

“ ‘Is there coverage for obesity?’ is yesterday’s conversation,” said Karen Ignagni, president of America’s Health Insurance Plans, an industry trade group. “Today’s conversation is how to design coverage to encourage people to use it and continue using it.”