(CNN) -- Football players guzzle protein shakes, down steaks and lift weights. They train and gain weight, hoping to build mass under the careful eye of the team's coaches, nutritionists and gurus.
Former Atlanta Falcon and Carolina Panther Chuck Smith had to adjust his diet and fitness habits.
"It was a scripted lifestyle where they tell you how to eat, how to take care of yourself, how much body fat you should have," said Chuck Smith, a former defensive end for the Atlanta Falcons and the Carolina Panthers.
But once their glory days are over, they have the same problem as millions of other Americans: They're fat.
"When I trained, they told us to eat all you can eat," said Smith, who played in Super Bowl XXXIII with the Falcons. "Drink beer, eat peanut butter to gain weight. All those eating habits were great for football. But when I got done, no question I had to make adjustments."
Without scheduled practices, meals, and games on Sunday, it became tougher to keep in shape.
When players were younger, they had the opposite problem.
Many tried to gain weight, believing that bigger is better. But as they age and retire from football, many are seeing that "big" is causing problems.
Smith, who weighed 274 pounds during his professional days, often had four plates of food in one sitting "to keep my weight up." After retirement, Smith had to unlearn those habits.
"I had to retrain my thinking," he said. "I don't need to be full. I don't have to stuff myself to feel comfortable. That took a long time. You stuff yourself to gain weight, then you get out of shape."
Smith learned he had high cholesterol (he had to take Lipitor), and his blood pressure was climbing, too.
"I had to take the bon-bons out of my mouth," said Smith, 39. "I had to empower myself. Strength coaches, nutritionists aren't going to take care of me. Guys have to empower themselves to take care of themselves."
Smith is now a fitness trainer at Defensive Line Incorporated, where he works with football players. Through healthy foods and workouts, he trimmed his body fat, lowered his cholesterol and shed 50 pounds.
Some players understand the risks, said Dr. Archie Roberts, a former National Football League quarterback and retired cardiac surgeon.
"They understand that if they stay 250, 300, 350 pounds as they age, that's going to shorten their life span and cause them more health problems," he said. "Others don't get it and they're unable -- for whatever reason -- to lose the weight, and they will suffer the consequences, just like anybody else in the general population carrying too much weight."
Diabetes, hypertension and high cholesterol are all cardiovascular risks associated with obesity.
Roberts heads the Living Heart Foundation, a nonprofit promoting health for former football players. For five years, he has conducted research to determine whether former football players are at added risk for heart problems (they're not).
After left tackle Bob Whitfield retired from the New York Giants in 2007, he gained 20 pounds. The 37-year-old Pro-Bowler is trying to lose 40 pounds, which would bring him to 290 pounds, the lowest he has weighed since ninth grade.
"You don't want to be the person at the buffet and people look at you crazy," Whitfield said. "Overall, you want to have a healthier lifestyle. It doesn't mean you want to be muscled up. ... I don't want to be the biggest man in the room anymore."
Looking back at his career, Whitfield doesn't think his size made him a better player.
"When that mass gets too heavy, you decline, you can't accelerate, you don't have as much force," he said. "I never felt that being bigger gives you a competitive advantage. I put it on flexibility, the explosive nature of your movements."
Several decades ago, 300-pound players were a rarity; now, the league has more than 500, Roberts said.
Decades ago, the Washington Redskins' offensive line was known for its size and dominance.
"They had the largest line in the NFL, called the Hogs, 20 years ago," said Dr. Ben Levine, director of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital in Dallas, and professor of medicine. "If you go back and look at their size, they're about the size of the running backs today. The impression was these guys were massive, huge. They couldn't play in the NFL today. They're too small."
Smith said he wasn't forced to gain weight, but perceptions exist on how a player should look based on his position. That "needs to change in the NFL," he said.
Being faster, stronger and more aggressive is more important than size, Smith said. He drew an analogy to airline stewardesses: "We want her to be tall and slim so she can walk down the aisles. Now is there really a difference between a 135-pound woman and a 150? Well, maybe a little bit different in the hips, but the same effectiveness happens when she does her job."
He added, "I'm a classic example that size doesn't matter."
But that's not what young, aspiring players think.
Jackie Buell, director of sports nutrition at Ohio State University, said she encounters players who seek to gain as much as 30 pounds by next season and seldom care whether it's fat or muscle.
Buell's research examined 70 college linemen and found that nearly half have metabolic syndrome, meaning that the players have at least three of the five risk factors of developing diabetes and heart disease. Her next project is to explore whether junior high and high school football players are developing metabolic syndrome.
"My fear is, these young men have this metabolic profile, what happens when they stop working out intensively?" Buell said.