The military has had weight and fitness standards since the Civil War, when they were instituted to guarantee that troops would be fit for armed conflict. Until 2001, the standards focused simply on weight and body fat, as measured by neck and waist measurements. In 2002, the Defense Department added BMI, a fairly complex formula but one commonly used by public-health experts to calculate ideal (and less than ideal) fat-weight ratios.

Body of evidence. Some believe that adding BMI won't necessarily clarify fitness or readiness. A 2002 study by Friedl and others showed that among some 1,400 male and female soldiers at three Army bases, 31.5 percent of men and 16 percent of the women had BMIs over 27.5, the military's new upper limit; yet 38 percent of the men and 56 percent of the women were over the old weight standards. And to complicate things more, only 11 percent of the men and 17 percent of the women were "overfat." Friedl has also found that as many as a quarter of the male soldiers who are both overweight and overfat have excellent fitness-test performance. In fact, he has suggested that the military give a body fat "credit" to personnel who are overweight but physically fit.

But for the time being, thousands of service men and women are struggling to meet the existing fitness standards, hoping to avoid being sent to a mandatory "fat boy" weight-loss program, a black mark on a military record. "Some of these kids have had very little training in how to manage their weight," says Lt. Col. Gaston Bathalon, an Army dietitian. "So they resort to dangerous and unhealthy practices."

Indeed, studies indicate that some women and men in the military use laxatives, diuretics, and other extreme measures to meet the weight standards. In a 2001 survey of more than 1,200 women from all branches of the service, nearly 19 percent of those in the Army and 38 percent of female marines said they fasted to control weight. More than 13 percent of Air Force women and 28.6 percent of female marines took diet pills, 12 percent used laxatives, and 2 percent to 3 percent vomited. Air Force personnel in a traditional "fat boy" program, 65 percent of them men, reported that they vomited and used diuretics or saunas four times as often as a group of civilian dieters. "For sure, we're causing people to do crazy things," says Friedl. "And these don't enhance readiness."

When extreme measures don't work, some people are forced to leave. Over 1,400 military personnel were kicked out of the services last year alone for failing to meet weight and body-fat limits. Thomas Fryer, 33, was discharged in 1997. A highly trained sonar technician, Fryer was overweight when he enlisted. But, he says: "I was an excellent sailor. I had excellent evaluations. I had no intention of leaving the Navy." Fryer had hoped that the Navy would place higher value on his expertise than on his BMI. It did not. He is now part of a class action suit against the Pentagon involving 2,600 former service members who have been told to repay their enlistment bonuses because they've been discharged for failure to meet weight standards.

Recruiting. Ultimately, the military's most serious weight problem may be finding young people thin enough to pass muster in the first place. Of Americans 17 to 20, 13 percent to 18 percent of men and 17 to 43 percent of women exceed the military's weight standards. Among minorities, the proportion the military would deem overweight is even larger. Eight in 10 of all recruits who exceed the weight standards when they join end up leaving before finishing their first term--making recruitment and training costly.

Because of this, the military has become serious about weight control. The Army is developing a computer-based weight-loss program aimed at getting soldiers to balance calories with exercise. The Air Force is also working on an Internet tool, which may include behavioral counseling.

As for Commander Cullen, a month ago she enrolled in the Navy's innovative Ship Shape Program, a voluntary program that focuses on nutrition education, lifestyle change, and exercise, as well as inspirational methods from successful commercial plans. Since she started Ship Shape, Cullen has jogged nearly every day and has lost 5 pounds. She wants to lose 20 more before taking the physical readiness test next spring. But for the first time in a long while, she is feeling confident she will pass.