Even if veterans are in the best shape of their lives when they leave the service, maintaining that enviable physique is an uphill battle–one that many veterans lose.

Last year, the U.S. Army found that its retirees were more likely to pack on the pounds than their civilian counterparts.

“Approximately half of the Army retirees whose height and weight were measured at medical appointments in military treatment facilities last year had a body mass index that classified them as obese,” the Army wrote in an article explaining the phenomenon. “Obesity rates for these retirees are significantly higher than the general population of the same age.”

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The Army suggested that this trend is caused by the sudden drop in physical activity after leaving the service and a failure to adjust caloric intake. A regularly exercising soldier at the top of his game may be able to eat three hamburgers in a single sitting, but when that same soldier drops his exercise regimen after retirement, those burgers come back with artery-clogging vengeance.

The hard truth is that the only way to stop the slow march to obesity and get back in shape is to make fitness your lifestyle. According to Nadine Dumas, a blogger for fitness brand Cellucor, anyone can make their tubby American bodies great again by changing their habits little by little.

“If you’ve experienced a setback, the worst thing you can do is rush to make up for lost time,” Dumas wrote on the Cellucor site. “Guilt from skipping the gym and overindulging often leads to excessive amounts of cardio and extreme dieting. Trust me when I say, doing this will only backfire. Make small, positive changes and you’ll gain momentum once again.”

Just because you weren’t in the Army or aren’t yet retired doesn’t mean your health isn’t in trouble too. In 2013, the Pentagon reported that 51.2 percent of all current service members were overweight, most often in the Coast Guard (57.2 percent). To help more military members pass is physical training tests and stay in the service, the Navy and Air Force adjusted their standards so the tests are easier to pass.

Small changes you can make in your lifestyle today include shrinking meal portions, putting more protein into your diet and doing something active everyday. A helpful resource for a drafting a new exercise regimen is the Army’s Performance Triad, a long-term workout plan devised by the military.