Burn, baby, burn.

Throughout the 7 years that I have been working in the health and wellness field, 8 out of every 10 people I see have expressed a desire to decrease their body fat. It's a great goal, since obesity is increasing at an epidemic rate in this country.

Currently, 61 percent of Americans are overweight, and one-third of them are obese. It is expected that, in the next 10 years, deaths related to obesity will surpass those related to tobacco as the number-one killer of Americans. Thus, it is vitally important that Americans get active and decrease their body-flit levels.

To lose body fat, it is essential that you follow a healthy diet and a regular exercise program. Remember, weight loss primarily comes from eating healthy, low-flit foods and minimizing the intake of refined, processed carbohydrates. Exercise does not give you free rein to eat whatever you like--unless you work out 6 hours a day! Exercise is much more beneficial in maintaining weight loss and in providing immense health benefits than it is in producing weight loss.

A key point to remember is that it actually is better to be obese and physically fit than to be lean and sedentary. Individuals who are lean but not physically active are at twice the risk for cardiovascular death than their counterparts who are obese but physically active.

Your Diet Makes a Difference

Okay, so you understand and are following a low-fat, high-fruit, and high-vegetable diet.

Sure, I know, you are sitting there saying, "Dave, what about the high-protein diets?"

Hey, I didn't say there was anything necessarily wrong about consuming a slightly higher protein intake, but a low-carbohydrate diet is not wise. This has been proven at the world-renowned Cooper Institute, where researchers have had hundreds of successful weight losers maintain a diet of choice that has the highest percentage of calories coming from carbohydrates.

So don't let the hype throw you off course. Eat small, frequent low-fat meals--especially breakfast--throughout the day and avoid processed and high-sugared foods.

Determining the Intensity of Your Exercise Regimen

Now, let's take some time and talk about how to use exercise to assist in reducing body fat. It has been a common misconception in the health industry that exercising at low intensities is the best way to burn body fat. To understand intensity, we briefly have to address heart rate training.

Intensity, or how hard you are exercising, can be gauged by several methods: the talk test, rate of perceived exertion, heart rate, and V[O.sub.2] percentage. (V[O.sub.2] training is more applicable in performance laboratory testing, so we won't discuss it here.)

The talk test simply means that you exercise so you can carry on a conversation. If you are unable to complete sentences while you are exercising, then you need to slow down.

To gauge the rate of perceived exertion, use a scale such as 1 to 10 or 6 to 20, the lowest number indicating a very easy intensity and the top number indicating a very hard workout. And, of course, you have all the levels in between.

Now, with heart rate, the standard rule of thumb is first to estimate your maximum heart rate (MHR), assuming you have never had your true MHR measured. To do this, simply take the number 220 minus your age. Thus, if you are 30 years old, your estimated MHR would be 190.

There are other prediction formulas out there, but this one seems to work reasonably well for individuals under 60 years of age. This value indicates that if you work out as hard as you possibly can, your heart rate would not increase any higher.

Establishing a Target Training Zone

Continuing on, the next step would be to identify a given percentage of your MHR to establish a target training zone. (There is also the Karvonen, or heart rate reserve method, used to calculate heart rate zones. It is a better method for regular exercisers, but it is not essential for this discussion.)

Many people--and that includes professionals in the field--recommend exercising at 55 to 65 percent of one's MHR. For the 30-year-old in our prior example, that would correspond to a heart rate zone of 104 to 124. At that level of intensity, the body uses a higher percentage of flit calories, compared to carbohydrates, since it relies heavily on fat as a fuel source.

But the amount of calories expended at such intensities is very low. As exercise intensity increases, the percentage of fat calories burned decreases, but the actual amount of fat burned increases. This is because the total caloric expenditure increases dramatically as your body works harder. More importantly, it is the calories burned that dictates flit loss--as opposed to whether the calories come from fat or carbohydrates.

Some people believe that one needs to exercise at least 20 minutes before the body starts burning fat. That is not correct. Remember, you can predominantly use your anaerobic energy system only for about 90 seconds. After that time, your body will start relying more on the aerobic system (that is, fat burning) if exercise is to continue.

It is true, however, that the longer you exercise, the more fat will be burned. This is because your body has limited stores of carbohydrates but a vast store of fat. Your body will definitely expend more fat calories the longer the exercise session is performed.

In case you're scratching your head at this point, just remember that your body always is burning a mixture of carbohydrates and fats. The more aerobically trained you are, the more efficient you become at using fat as an energy source. And, to become more aerobically fit. you must train at higher intensities.

I'll leave you with one question to answer, given what you've learned: Elite marathon runners run 26.2 miles at 85 to 90 percent of their MHR. What is their primary fuel source during this run?

Take-Home Points

* If time is held constant, the harder you work out, the more total and fat calories used.

* There is no "flit-burning zone." Don't use the far-burning programs often seen on cardiovascular gym equipment.

* There is nothing wrong with training at lower intensities. Your body can't go at warp speed every workout--and long, slow workout sessions are needed for physiological and mental recovery.

* Try to increase the speed of your workouts. Using interval training is a great way to accomplish this task.

* To lose weight, you must expend more calories than you consume to lose weight. Unless you were abducted by extraterrestrials and have alien DNA, you can't violate the first law of thermodynamics.

* As of today, there is no safe magic pill to replace exercise and diet as a means of reducing body far and increasing health benefits.

David J. Holes is a health educator for the Fit To Win program at the DiLorenzo TRICARE Health Clinic. In addition to his duties in planning and instructing health promotion classes, he also serves as a staff exercise physiologist/personal trainer for the program. He thoroughly enjoys working with people and helping them understand how to lead a healthy lifestyle.

He received a dual B.S. degree in physiology and kinesiology from the University of California and an M.A. degree in exercise physiology from the College of St. Scholastica in Duluth, Minnesota. He holds personal training certifications from ACSM, NSCA, ACE, and the American Academy of Health Fitness and Rehabilitation Professionals.