On February 3, the Baltimore Ravens and the San Fransisco 49ers will face off in the 47th Super Bowl. When they sit down to watch fans will see players on the field like the Ravens’s Haloti Ngata, a 6’4”, 340 pound defensive end. Bryant McKinnie, the left tackle for the Ravens, is 6'8" and 360 pounds. Leonard Davis, on the 49ers, is 6’ 6” and 355 pounds. Fans and players alike understand some of the risks that come with two 350 pound men slamming into one another. The hidden, long term risks of repeated head injuries have dominated the football headlines this season. But the risks go beyond torn ligaments and bashed heads. Bigger players also have to deal with the side effects of their sheer size – things like obesity and metabolic disorders, that stay with them long past their playing days.

Bigger is better

Football players have always been big, but today’s players are truly huge. A recent study found that every year since 1942 players at all positions, from quarterbacks to centers, have gotten heavier. The change was most noticeable for linemen - who gained, on average, from .7 to 2 pounds each year. Applied to the whole span of time that the researchers looked at, that's an increase of almost one hundred pounds since 1942. When they looked at what kind of weight that was - muscle or fat - they found that linemen were adding from 0.05 to 0.3 percent fat each year - something like an 11 percent increase in body fat percentage since 1942.

Anecdotally, to long time football fans this seems obvious. Take Roosevelt Brown, a star tackle for the New York Giants from 1953 to 1965. In his career, Brown played in nine Pro Bowls, and was named one of the 100 greatest football players ever by The Sporting News. Brown wasn't a small guy, coming in at 6' 3" and 255 pounds. But stacked up against today's tackles, he wouldn’t stand a chance. Flozell Adams, now a free agent but a long time offensive tackle for the Dallas Cowboys has five Pro Bowls under his belt. He's 6'7" and 340 pounds. Just four inches taller, but nearly 100 pounds heavier. There are all sorts of examples like this. Compare star centers - Chuck Bednarik from the 1950's and Andre Gurode today and you see the same thing. Bednarik was 6'3" and 233 pounds - Gurode is 6'4" and 318.

In fact, despite being some of the top athletes in the game, some active NFL players are clinically obese. "From a coaching standpoint, it makes a lot of sense to have the biggest possible person that you can have," says Dale Wagner, a researcher at Utah State University who looked at the prevalence of obesity in NCAA football players. One study, published in the Journal of the American Medical Association, looked at body mass index in NFL players. They concluded that 97 percent of current NFL players were overweight, and 56 percent of them qualified as obese. Wagner says that using BMI on a professional athlete is misleading - the index isn't designed to characterize people who spend the majority of their time working out. But if the NFL is anything like the NCAA, the percentage of obese players is probably still something like 15 percent.

The push for bulk

There are a lot of reasons why football players are bigger now than they used to be, says Jeffrey Potteiger, researcher at Grand Valley State University, who recently published a study tracking the size of football players from 1942 to 2011. Some are obvious: "we've gotten better at how we train players, we've gotten better at how we feed players." In 1978, the National Strength and Conditioning Association was founded by a group of strength coaches to help codify and legitimize a vast-growing profession. Hundreds of studies have been done to understand exactly what combination of protein and carbohydrates will give athletes the edge. Combined with likely illicit steroid use, better training and better food simply means bigger players.

But it's not just a technological improvement. Rule changes in the NFL likely contributed to incentivizing a bigger heavier player too. Up until the 1970s, it was legal for players to block below the waist - a move known as "chop blocking." But in 1970, the Rules Committee voted unanimously, 23-0, to ban chop blocks, calling the move "unethical" because it seemed to be causing serious knee and ankle injuries. The result was probably fewer knee and ankle injuries, but the rule change precipitated a huge boom in weight lifting. Players now needed to be big and sturdy, and extend their arms out straight to block above the waist.

The combination of this rule change and the advent of modern strength training seems to have set football on a steady course towards bigger and bigger players. And many coaches seem locked into this trajectory. "It's like an arms race," says Potteiger, "whoever can be the biggest strongest person out there gains the advantage on the field." When one team has Andre Gurode at center, the other team has to respond by putting a similarly sized player against him. When your defense is playing against a 6'7", 350 pound Flozell Adams, they need someone who can keep up. "Because in a jump ball the 6' 7" guy is always going to win," says Potteiger. Wagner agrees, saying that if one team has a bigger stronger line, they're going to have the advantage. And if coaches are comparing two similar players, they're almost always going to choose the larger one. "If they can run the same 40 yard dash, if they can jump just as high, they're going to pick the bigger person," says Wagner.

Of course, this push towards heavier, bigger players doesn't just impact the NFL. As professional players get bigger, so do college and high school players. The University of Florida has 16 players over 300 pounds on their roster. Elder High School, which has a famed football program, has ten players that weigh in over 250 pounds. And the earlier they start, Wagner says, the more likely they are to be able to get really big. "Just consider that most of these folks have been training through high school, through college, maybe 10 years of training to get to that point," Wagner says.

Bigger is better, but also worse

Bigger players mean a lot of things for football. First, more mass means more force - the bigger the players are, the more dangerous their collisions are. Research has uncovered the long-term dangers of repeated head trauma, and while it's likely that these sorts of injuries have been around since the beginning of football, Potteiger says, bigger players certainly aren't making it better.

But the effect of heavier players goes beyond physical injury like broken bones, or concussions. Heavier people have higher blood pressure, higher risk of heart disease and metabolic disorders like diabetes. One study looked at 510 retired NFL players and found that nearly 60 percent of linemen had metabolic syndrome, while non-linemen were far closer to the national average of about 23 percent. In the NCAA, 48.6 percent of linemen had at least three risk factors for metabolic syndrome during.

Many of the risks of being that big don’t show up during a player’s career, either. During the season, while big, most of these players are fit - they exercise and lift weights, they're monitored by training staff, and they perform on the field. Shaun Rogers, a offensive tackle with the New Orleans Saints, weighs 350 pounds. But he can also run a 40 yard dash in 5.3 seconds. It's after their career ends, Potteiger says, when many of these players might find themselves saddled with the repercussions of their weight. Many have trouble slimming down in retirement, and a study of former NFL players found that football retirees have a higher rate of arthritis than the average population.

Which raises the question of the NFL's responsibility to those bigger players once their career ends. "For 3-5 years they've told these players to gain weight, gain weight, get bigger, get bigger," says Potteiger, "and now they have cardiovascular disease and high blood pressure." The NFL has committed $30 million dollars to research into the long-term effects of head injuries, but they're largely silent about the metabolic troubles that all that increased weight can bring on. There's little in the way of help for players to slim down after their careers - and for people who have spent 20 years getting big, breaking those habits is hard. "If NFL players and college players are encouraged to gain all this body weight, doesn't the league have some level of responsibility to help that individual lose weight and become more healthy after their career is over?" Potteiger asks.

The future football star

Of course, there is a limit to just how big players can get. No one is sure what the upper physical limit is, but Potteiger thinks we're close. "At some point in time, they can only get so big, and I've got to believe that we're getting close to that upper limit." As players approaching 350 pounds, it's hard to imagine a much heavier team being able to keep up.

There's also more to football than just being the biggest on the field, says Potteiger. "You can't just take 11 physical specimens and put them out there on defense and expect them to do well." Which is something, he says, that many coaches seem to have forgotten in the race for size. As coaches look for a physical match for their opponents, they overlook players who might be smaller, but smarter. "Often what I hear is coaches or general managers will talk about the physical abilities of the players," Potteiger says, "and there's physical ability there, but yet they aren't very good at playing the game."

The future of football doesn't have to be a battle of giants though. If a team were to break from the arms race, and assemble an offense of smaller, smarter and quicker players, they could throw the league for a loop. That's essentially what that Washington Redskins did the early ’80s when Charlie Brown, Alvin Garrett and Virgil Seay - three small wide receivers all around 5' 9" - helped the Redskins win the Super Bowl. These little receivers – nicknamed “The Smurfs” – were smaller, but quicker than the defensive backs they were playing. The type of offense a team plays could also break the bigger-is-better tradition. A coach who came straight from a college system, like Chip Kelly who left the University of Oregon to be head coach for the Philadelphia Eagles, could bring with him a fast paced offensive style, and some of the biggest players might soon find themselves outpaced.

But Potteiger isn't holding his breath for any of that to happen. "I think it will continue to be like an arms race," he says. "Teams will continue to look for the biggest and the best athletes." It's simple math, really. Aaron Gibson, who retired in 2004, was 6' 6" and 440 pounds - possibly the biggest player ever. King Dunlap, currently with the Eagles, is 6 '9" and 330 pounds (that's just four inches shorter than Shaquille O'Neill, and five pounds heavier). And in just a few weeks, when the Ravens face off against the 49ers in the Super Bowl, the two teams will have a combined 26 players over 300 pounds. So for the time being, the motto of the NFL still seems to be "go big or go home."