The Firefighter Fitness Pentagon: Part 4 – Body Composition

April 1, 2004
Rod Hammer reports on the need for firefighters to lose weight and become healthier in order to reduce health risks.
Heart attacks have been the leading cause of firefighter fatalities for the past 30 years. On average, between 38 and 50 firefighters die each year of heart attacks. In addition, nearly 1,000 non-fatal heart attacks occur annually to on-duty firefighters.

Obesity has been associated with an increase in chronic disease and health conditions according to the American College of Sports Medicine. In fact, there is a strong correlation between being overweight or obese and the increased risk of heart disease, high blood pressure, diabetes and high cholesterol. All of these factors increase the likelihood of having a heart attack during extreme physical exertion.

Most people are under the impression that firefighters are strong and healthy. Perhaps that is also the assumption of many in the fire service. While this may be true in some departments, reality may be less comforting. In a recent study, 82% of career and volunteer firefighters were overweight or obese. This is appalling, considering the national average of overweight and obese adults is a whopping 65%. Another study showed that the average firefighter is overweight and nearing obesity. Ironically, we have an overweight nation protected by an even more overweight fire service.

This sounds harsh, but it is time we face the facts and decide if each one of us needs to make some changes. We can’t presume to be able to safely fight fires if we have health risks associated with being overweight and obese.


Researchers who look at the effects of being overweight or obese use the Body Mass Index (BMI). This index is a comparison of weight to height. The healthy weight recommendation is a BMI between 18.5 and 25. Between 25 and 30 is considered overweight and greater than 30 is classified as obese. Use the Body Mass Index table on page 102 to find your BMI value by finding your height in the left column and your weight in the top row.

While this measure is not exact, it is a good indication of your potential for health risks due to excess body fat. In fact, BMI is the number most used in obesity research. It should be noted that those of you who are very muscular with low body fat might inaccurately be given a higher BMI number. You should use a different measurement technique.

Besides the Body Mass Index, body fat is also discussed in terms of percent body fat. This is the percentage of your body mass that is made up of fat. The remaining tissue is referred to as the fat-free mass, for obvious reasons. Percent body fat is considered healthy if it is below 20% for men and below 25% for women.

Percent body fat can be measured using a variety of testing methods. Hydrostatic weighing is considered the “gold standard.” You sit in a chair attached to a scale and are lowered into a pool of water. Using several calculations, your body fat percentage is determined. This method takes about 15 minutes to conduct and requires you to wear a swimsuit for testing. Hydrostatic weighing is usually done at hospitals and university research centers.

Another body fat percentage measurement method that is easier to administer than hydrostatic weighing is the measurement of subcutaneous body fat. Calipers are used to measure skin-fold thickness at various sites on the body. The skin-fold values are entered into an equation and again, percent body fat is determined. This method takes about 10 to 15 minutes to administer. Personal fitness trainers in fitness centers as well as technicians in hospitals and universities conduct skin-fold measurements.

This method is considered slightly less accurate than hydrostatic weighing because of the variance in measurement between test technicians. It is also somewhat uncomfortable because the technician has to pinch the skin to create a fold that can be measured. Accuracy can be difficult due to the large skin-fold size if the firefighter is obese.

A third method for measuring percent body fat is through bio-electric impedance (BIA). This method can easily be done at home using a BIA scale. You must enter your height, age and gender into the scale before it can accurately determine percent body fat. Most BIA scales are combined with a standard bathroom scale. The output is a digital readout of body weight and percent body fat. Another BIA device is a hand-held body fat meter. This device works in the same way as the scale, but does not have the ability to read weight. It has to be entered when you enter your age, gender and height.

Accuracy in BIA measures depends in part on your hydration status. Excess fluids will skew the reliability of the measure. It is important that you repeat the test under the same conditions as the original test. I usually require subjects to not eat or drink four to six hours before any body composition measurement. BIA may not be as accurate as hydrostatic measuring, but test/retest reliability is fairly good. If you use the same scale under the same conditions, the probability of showing differences in body fat gain or loss is very good.

Finally, a cheap and easy way to determine if you are at risk of heart disease is if your waist measures greater than 40 inches. Use a cloth tape measure to measure your abdomen at the level of the navel. If your waist is more than 40 inches around, you have a significantly higher risk of heart disease than those whose waist measures less than 40.

Weight Loss

Maybe you discovered that you need to shed a few pounds (or a whole bunch) after doing the body fat assessment. How do you do it safely and effectively?

Before we get into that, let me explain a little about our metabolism. Body mass depends on a balance between the energy consumed (food) and energy expended (movement or exercise.) Think of your body as a reservoir of water being held back by a dam. If the amount of water coming into the lake from a river is the same as the amount of water flowing through the dam, the level of the lake stays constant. It doesn’t rise or fall.

Your body acts exactly the same way. The food you eat is like the river flowing into the lake and your daily activity is the water flowing past the dam. The level of the lake increases if water is not allowed to continue through. Your body does exactly the same thing. If not enough energy is expended, you gain weight. If you expend more energy by exercising, it is the same as if you open the dam and more water flows out, causing the level to drop and you lose weight. Or, you could decrease the amount you eat. Just like a river at the end of summer, the amount of water flowing into the lake is reduced so that less water is entering the lake than is passing through the dam and the water level drops. Again, you lose weight. There is an equilibrium between energy intake and energy expenditure. This determines your body fat.

Your daily energy expenditure can be divided into three categories:

  • Resting metabolism
  • Daily activity
  • Exercise

We typically discuss this energy in terms of calories. Most of us are familiar with this. All food is required to have the number of calories in the nutritional guidelines on the back. For instance, a 12-ounce can of non-diet soda has 150 calories per serving. Your energy expenditure is also measured in calories. Each activity has a different caloric expenditure, depending on the activity and your weight. More of these will be described later.

Resting metabolism rate (RMR) is the amount of energy you burn when you are completely at rest. It typically accounts for 50% to 70% of your total daily caloric expenditure. You burn calories from the bodily processes required to keep you alive. This can be estimated by using the Harris-Benedict equations below:

Resting Metabolic Rate

Men = 66.473 + (6.25 x weight in pounds) + (12.71 x height in inches) – (6.75 x age)

Women = 655.0955 + (4.301 x weight in pounds) + (4.698 x height in inches) – (4.6756 x age)

For example, a 180-pound male who is six feet tall and 30 years old has a resting metabolic rate of: 66.473 + (6.25 x 180) + (12.71 x 72) – (6.75 x 30) = 1,904 calories.

Your daily activity caloric expenditure can be calculated using a multiple of your resting metabolic rate. Use the chart on page 102 to find the number to multiply to your RMR.

Multiply your RMR by the number that is next to your activity level. In the example above, our 180-pound male is a line firefighter. He finds his daily activity level by multiplying his RMR of 1,904 calories by 0.50 to equal 852 calories.

Any additional activity during your day will increase the number of calories you burn. These are activities like exercise. Each activity will burn a different number of calories, depending on your weight.

You can find tables on the Internet to see how many calories each activity burns. One good website for such data is For example, our 180-pound male firefighter runs on a treadmill for 30 minutes each day at 8.0 mph. He burns about 580 additional calories from exercise. To find the total daily caloric expenditure, you add the RMR, the activity level multiplier and any additional calories burned through exercise. Our firefighter would burn:

This firefighter has a pretty active lifestyle that leads to good caloric expenditure, but now we have to look at how many calories he eats. This is fairly easy to figure. You can look at the labels on food packages, or you can get on the web and find sites that can figure it for you. You just enter the food you eat and it calculates number of calories based on the food and the size of the portion. Again, works well for this.

Our firefighter starts the day with breakfast from the fast-food joint just down the road from the station. He has a sausage, cheese and egg muffin and a 12-ounce cup of coffee (with sugar). For lunch, he has time to grab a burger, fries and a soda (super-sized) between calls. Things slow down in the afternoon and he has time to eat most of a bag of chips sitting on the counter. The rookie cooks chili for dinner, and it actually tastes pretty good for a change. Our firefighter is hungry from working hard, so he has a second bowl with another soda. Later, he sits in the recliner and enjoys a candy bar and a 12-ounce soda before heading for bed. Let’s total his caloric intake:

Now, let’s compare his intake and his expenditure:

He is eating 733 calories more than he burns. That means that on a weekly basis he is eating about 5,000 extra calories. Since a pound of fat equals about 3,500 calories, he would gain one to two pounds a week, if he keeps this up.

As you can see, even with the exercise, this firefighter’s diet is causing him to gain weight. If he wants to maintain his weight, he must cut 733 calories or add another 40 minutes of running. Research has shown that individuals who exercise more than 280 minutes per week or roughly one hour per day for five days per week can maintain weight loss.

This is a general overview of how the body’s metabolism works. There is certainly much more information about other aspects of the diet. Volumes have been written about nutritional supplements, protein, carbohydrates, fats and just about every diet that creative people can come up with. The most popular diet right now is the Atkins high-protein diet. While it is true that many people have lost weight with this plan, it doesn’t mean it is right for everyone.

I recommend moderation and balance. Don’t try to lose more than one or two pounds per week. This is roughly the same as eating 500 to 1,000 calories per day less than you burn. Weight you lose will come right back if you don’t make lifestyle changes. Healthy eating has to become a habit if you want real change to occur.

It is important that we realize the need to lose weight and become healthier. Research has shown that weight loss of even 5% to 10% results in a dramatic reduction in the health risks discussed at the beginning of this article.

Whether you are a career firefighter spending 24 hours a day on shift or a volunteer who tries to grab something to eat before drill, most people have difficulty maintaining a balanced, healthy diet. It takes dedication, and sometimes re-dedication, to stay on track. Do the best you can to find something that works for you and be healthy.

Rod Hammer is a captain and training officer with the Lewiston, UT, Volunteer Fire Department. He has a master’s degree in exercise science and is the director of Human Performance Research at Icon Health and Fitness, a manufacturer of fitness equipment. Hammer also is the fitness coordinator for the Cache County Fire District. He consults with career and volunteer fire departments to establish firefighter fitness programs. Hammer can be reached at [email protected].

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