A new Pentagon study has found that the Navy is the fattest U.S. armed service, with almost one in four sailors obese.

In addition to heart disease, stroke, and other health problems associated with obesity, an overweight force could put essential ship operations at risk. "I think it's a real readiness issue," Jimmy Drennan, a U.S. Navy officer and president of the Center for International Maritime Security, told the Washington Examiner.

He explained that portly sailors could find it more difficult to navigate narrow ships. "Not just hatches, but passageways ... they are already very tight on U.S. Navy ships, compared to other navies," he said. "Not to mention the fatigue and heat stress of fighting a fire in full gear."

The Navy was the most obese service at 22%, beating out the Air Force on 18%, and the Army on 17%. The Marine Corps is by far the leanest service, on 8.3%.

Thomas Spoehr, a retired lieutenant general who researches health and obesity, said: "The U.S. military is a subset of U.S. society and America is the most obese country in the world, with over one-third of adults qualified as obese."

"The problem of increased obesity increasingly erodes readiness. Service members are less able to cope with physical loads and stress. Obesity is an underlying cause of many chronic diseases such as diabetes and heart disease. Obesity contributes to joint problems, especially knees and hips. All these issues contribute to service members unable to perform their primary mission when the need arises."

Lack of exercise, large portions, high calorie content, and less emphasis on physical education in schools, problems across society, all play a factor. Some military habits are also a problem, such as the notorious obsession with sugary energy drinks seen across all branches. "Sailors drink plenty of energy drinks and we know that's not healthy," Drennan said. "We get resupplied at sea with pallets of those things."

The Army has placed dietitians within its ranks and has made efforts to educate soldiers on the importance of healthy foods. The Navy has a Fitness Enrollment Program for sailors that fail fitness standards that includes mandatory weigh-ins and workouts.

There has been debate about how the military measures obesity. Currently, the Navy has separate maximum body fat standards for men and women, based on height and weight. Those who fail it are then subjected to a tape test, which measures the waist and neck to determine obesity. But there are complaints that the test is flawed and can unfairly disqualify troops who score well on physical fitness tests.

Spoehr believes a solution to the military's weight problem begins at the national level. "This is a national health crisis that needs to be addressed before it impacts the ability of the military to accomplish its missions," he said. "The Treasury cannot print enough money to pay for all the healthcare that will be needed to treat a population that is steadily becoming less healthy."