There are times when Matt Kalil is so full he can't take another bite. Yet he chews on because the consequences of not doing so are too dire to consider as a 21st century left tackle in the National Football League.

Giving in to his overwhelming craving not to maintain his consumption of 6,000 to 6,500 calories per day would cause Kalil to essentially shrink. Rapidly.

"I know, I know, 'Poor guy. Must be tough having to eat all the time,' " says Kalil, the Vikings' 6-7, 307-pound rookie. "But, really, it is sometimes. I mean there are times when I feel completely stuffed and it's time to eat again."

Carrie Peterson, the sports nutritionist for all the pro sports teams in town, never has seen anything like it. In the 10 years she has worked with the Vikings, Kalil is the first offensive lineman she has had to help gain weight. It's quite the reversal from 14 months ago, when the Vikings released their previous franchise left tackle, Bryant McKinnie, in part because he had let himself balloon close to 400 pounds.

"You've seen some of the old-school offensive linemen that we've had and actually dismissed, like Bryant, who just never bought into the [nutrition] program," Peterson said. "But Matt is a totally different guy to work with. He buys into the program because he's been trying to do the right things [nutritionally] for so long. He maintains the weight and takes care of it. The guy is just a machine."

The NFL's 'expansion'

Hall of Famer Art Shell was considered mammoth when he played left tackle for the Raiders from 1968 to 1982. He weighed 265 pounds.

Anthony Munoz, another Hall of Famer, joined the league in 1980, two years after revolutionary rules changes laid the foundation for what would become a passing league. Munoz played until 1992 and is remembered as perhaps the greatest modern-era left tackle in league history. His weight: 278 pounds.

Neither Shell, nor Munoz, at their playing weight, would have been a match for the guy Kalil will help block Sunday at Mall of America Field. Calais Campbell, an end in Arizona's 3-4 scheme, has never made the Pro Bowl or been selected an All-Pro. But he is 6-8 and 300 pounds.

"That's a big man," Vikings coach Leslie Frazier said. "He creates problems just with his sheer size alone."

In 1970, the NFL had one 300-pound player. In 1990, it had fewer than 70. Last year: 354. Talk about incentive to keep chewing.

"I don't think naturally that I'm meant to be 310 pounds," Kalil said. ''If I wasn't playing football, I'd weigh 240, 250. But gaining weight, putting it on the healthy way has been something I've done my whole career."

Father did know best

Neither one of Frank Kalil's boys wanted to be offensive linemen at Servite High School in Anaheim, Calif. Ryan, the center in Carolina, wanted to play quarterback. Matt, the fourth overall draft pick this year, had visions of catching touchdown passes as a tight end.

"Ryan was no quarterback and maybe Matt could have played tight end," said Frank, who had a brief career as a lineman in the USFL. "But they weren't playing much when they were younger. And my philosophy, which I told them, was the most important thing was to get on the field."

So the Kalil boys became linemen.

"You had two slender, fast, athletic kids playing the line against a bunch of fat kids," Frank said. "So Ryan and Matt stood out."

Putting healthy weight on his boys was like an ongoing science project for Frank. Protein shakes mixed with peanut butter, carbohydrate mixes and five well-balanced meals a day were combined with rugged weight training, cardiovascular work and intense line-specific drills at a nearby park.

"Ryan is 27 and Matt is 23, so Ryan was like our test kitchen for Matt when it came to nutrition," Frank said. "So many kids get involved with illegal substances and drugs and enhancers and all this stuff. But we always preached to do it the right way. No shortcuts. I laid out the road map for them, but they worked their butts off and that's why they're in the NFL today."

As a high school freshman, Matt was 6-3 and 185 pounds. He was 240 his sophomore year, 275 as a freshman at Southern California and 295 as a senior.

The new prototype

Probably the worst Kalil felt in years was when he put on 16 pounds in a hurry for the pre-draft NFL Scouting Combine. He was 311 pounds and yet every team he visited with had the same No. 1 question for him.

"How much weight do you think you can gain?" Kalil said. "That's all they seemed to want to know."

He had his answer polished by the time he sat down with Frazier.

"He told me, 'Coach, I'm going to change how left tackles look in the NFL,' " Frazier said. "He said, 'My lean build is going to create more left tackles who want to be like me. They'll want to have this basketball build so that they can mirror these fast defensive ends.

"I said, 'We'll see. We'll see.' At the time, he didn't know that we were going to ask him to gain weight, too."