It fills weight rooms throughout Bismarck. It's responsible for clanging iron and the whirl of aerobic equipment. It motivates people to run an extra mile or force out another rep.

The look. A combination of low body fat and plenty of lean muscle mass. Ripped, shredded and cut are some of the words used to describe it, but hard work in and out of the gym is about the only way to obtain it. And according to local personal trainers and workout enthusiasts, the hard work only begins after weight training and aerobic exercise ends.

A key to developing and maintaining the desired body is nutrition, according to certified physical trainers Jamie Grismer and Derek Ternes of Nutri Sport and Optimal Fitness and Renita Brannan of Focus Lifestyle Coaching and Pilates Studio.

Grismer has a bachelor's degree in exercise science and is National Endurance and Strength Training Association certified. Ternes is certified to train by the American Counsel on Exercise and the World Instructor Training School. Brannan also is ACE certified and has a bachelor's degree with an emphasis in physical education.

Shunning the USDA Food Guide Pyramid and fad diets, they say a nutritious lifestyle requires more meals and, for some, added calories.

"The food pyramid is a guide to obesity," Grismer said.

"If you eat according to the food-guide pyramid you'll look like the food-guide pyramid," Brannan said.

Grismer, a former high school, college and Arena football player who once tipped the scales at 330 pounds, lost 100 pounds and kept it off by monitoring his carbohydrates. He said the key to reaching a healthy body fat level is "figuring out your carbohydrate sensitivity level." Carbs are found in a variety of foods, including bread, cereal, fruit, vegetables and potatoes.

"It's finding out that right carbohydrate level for you because everyone is different," Grismer said. "Protein and fat won't make you fat, it's too many carbohydrates."

Finding the carbohydrate level that works requires trial and error and consideration of the types of carbs being consumed, he said. Keeping carbs as low as possible is a must, but dizziness, weakness or cravings means levels are dipping too low.

"Take in the least amount of carbohydrates as you can while maintaining your energy levels," Grismer said. "That's the key to a lean body."

Carbs are digested at different rates, depending on their glycemic level - high, medium and low. Most fruits and potatoes have a high glycemic level and are quickly released into the body while vegetables and other high-fiber sources have low levels and take longer to digest, Grismer said. An index rating glycemic levels of foods can be found in some health food books or on a variety of Web sites such as http://www.glycemicindex.com.

Grismer recommends filling carb quotas with low glycemic or "complex carbs" because more energy is burned digesting them. The best time to fill cravings for high glycemic or "simple carbs" is after exercise because they'll be used in recovery and won't be stored as fat.

"After a workout you want high glycemic carbs to replenish your body," Grismer said.

While keeping carbs low, protein levels should stay high - one to one and a half gram per pound of body weight, Grismer said, although Brannan recommended a maximum of .75 grams of protein per pound of body weight.

People who lift weights need more protein to repair micro-tears in muscles during weight training. Natural sources, such as egg whites, poultry and beef, are the best choices - provided they are lean and trimmed of visible fat - but supplementing with a whey protein found in bars and powders makes it easier to reach high protein levels, Grismer said.

Weight-lifters should drink plenty of water to offset any potential damage to the kidneys caused by the added protein.

Cutting out fat isn't the answer to weight loss and can hamper workout recovery and cause joint aches, Grismer said. Find the "good fats" and stay away from saturated fats found in beef, butter and dairy products. Some good sources include flaxseed and olive oil and fats found in fish and nuts.

The timing and makeup of meals also is crucial. Six to eight small meals made up of protein, carb and fat sources should be spread out evenly throughout the day, Grismer and Brannan said. Making your body constantly work to digest speeds up metabolism, which helps burn fat.

"Keep feeding that motor all the time. It will speed up metabolism," Grismer said.

Weight lifting and aerobic exercise also will speed up your metabolism. Ternes says weight training increases metabolism levels in the long run because added muscle burns extra calories.

But the heart also is a muscle, so aerobic exercise such as running or biking is needed to stay healthy. Grismer recommends aerobic exercise four to seven days a week with a target heart rate of 60 percent to 80 percent of your maximum heart rate - the number of times your heart beats when you are working at maximum capacity.

"Listen to your body. Learn your body" Grismer said. "It will tell you everything."

Brannan says not to take diet to an extreme. She said that while competing for Miss Fitness North Dakota in 1999, she cut her calories to 1,000 a day and was eating less than 10 grams of fat and no carbs. Although she won the contest, she said her body suffered and her metabolism was wrecked for life.

Kelly Fisher, a licensed and registered dietitian at Medcenter One, said she agrees with some components and disagrees with others. She said 30 percent of calories should come from fat, and agreed that everyone should consume the aforementioned healthy fats and avoid saturated fats.

Protein levels shouldn't exceed a half a gram per pound of body weight, she said. Too much protein is hard on kidneys and drinking more fluids won't save them, she said.

"They may never see kidney problems, but they may be at a higher risk," Fisher said. "It could increase the possibility of them having problems with their kidneys later in life."

Carbs should make up 50 percent of the daily caloric intake to restore glycogen stores, Fisher said. Low carb levels can cause hypoglycemia or low blood sugar.

"If you're not getting enough glucose you're not able to think clearly," Fisher said.

She said high fiber intake is good and everyone should focus on consuming carbs high in fiber.

"Get a balance of all kinds of foods," she said. "You shouldn't be eating the same kinds of foods all the time."

(Reach reporter Mike Albrecht at 250-8261 or cops@ndonline.com.)