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The Truth About Exercise Intensity and Weight Loss: Old Myths and New Realities

Thomas Fahey, Ed.D.

Sixty percent of women are overweight and most will remain that way because they don't have the will power or knowledge to lose body weight. That's understandable because we live in a no-fault society that makes it easy not to take responsibility for anything. It's painless to blame cellulite and an expanding dress size on genetics, time restraints, stress, birth control pills, family, or a recent pregnancy. Also, women hear so much conflicting information about diet and exercise that it's difficult to know what to do. Obesity is not inevitable- millions of women face challenges, yet manage to stay lean and fit.
Some experts think the obesity epidemic is unsolvable and that America is destined to drown in its own fat. That's a copout. We have not always been a nation of fatties, and people in many countries around the world are still largely lean and fit. A new spectator sport in some countries is to go to the airport and count the number of fat Americans getting off airplanes. Don't be imprisoned by excess fat. Exercise vigorously and watch what you eat and in six months you will have a lean, shapely, healthy-looking body that will turn heads.

How Much Exercise Do You Need to Lose Weight?

In 1996, the US Surgeon General's office recommended that people exercise moderately for 30 minutes, preferably every day of the week. Acceptable activities included mowing the lawn, waxing the car, walking from the car to the supermarket, and gardening. This was a far cry from past recommendations that asked people to exercise 20-60 minutes, 3-5 times a week, at 60-85 percent of maximum effort.

Why did the Surgeon General's report recommend less intense exercise than before? They sold out! Only 12 percent of Americans followed vigorous exercise programs. Rather than tell the truth about how much exercise people really need, they reduced the exercise recommendations so that more people would exercise. They reasoned that getting many people in the country to do some moderate intensity exercise was better than a small group of people exercising intensely.
What's happened since the 1996 Surgeon General's exercise report? Obesity rates skyrocketed and people are no more active than they were then. In some states obesity rates have climbed more than 100 percent in only three years. To make matters worse, people no longer had to feel guilty about exercising vigorously because the Surgeon General's office told them it was okay not to. The US National Academy of Sciences and the World Health Organizations- in separate reports- recognized that exercising moderately for 30 minutes a day will not help people lose weight, let alone make them look lean and fit. So, each group recommended that people exercise 60 minutes or more per day.

Americans do not want to be fat. The mega sales of books such as Dr. Atkins Diet Revolution and The South Beach Diet and our national obsession with fit, lean celebrities like Janet Jackson, Angelina Jolie, Demi More, and Brittany Spears show that Americans want to be healthy-looking and have nice looking bodies. Unfortunately, most of us aren't willing to work hard enough to achieve these goals. If you are overweight, do you want to stay that way, or are you willing to do the work it takes to create a new you?

Old Myths and New Realities about Exercise Intensity and Weight Loss

Elegant studies by Dr. George Brooks from the University of California, Berkeley showed that the body uses mainly fats for fuel at rest and low exercise intensities. Above 65 percent of maximum effort the body switches abruptly to carbohydrates and uses much less fat. The rate of fat breakdown in fat cells also decreases with increasing exercise intensity. The best method for losing weight through exercise looks like a no-brainer: train at low exercise intensity because you use fat as fuel. The studies suggest that the longer you exercise, the more fat you use as fuel and the more body fat you'll lose. Exercise equipment manufacturers have taken note of these studies and have included so-called fat burning zones programmed into treadmill workouts that have people exercising at 30-60 percent of maximum effort.

The real answer to the question of how to lose fat through exercise is not so obvious. True- you use more fat as fuel when you exercise moderately. But, you lose more body fat when you exercise intensely during a 24-hour period because you use more fat for fuel and increase metabolism (increase calorie use) more after exercise. Also, you burn more calories during the exercise itself. The total daily energy use is more important for fat loss than the kinds of fuels used during exercise.

You lose fat by using more calories than you take in. You will burn many more calories training intensely than exercising slowly. The body does not metabolize fats by themselves. Rather, fat use is integrated with carbohydrate and protein metabolism. Even if you used more fat during exercise, fuel storage balances itself out according to energy balance - calories in versus calories out. Intense exercise causes you to burn more calories and fat after the exercise is over. So, when trying to lose fat, work harder and burn more calories.

Intense exercise builds muscle tissue- particularly if you include weight training in your program. Muscle uses more calories than any other tissue in the body. The more muscle you have, the more calories- and fat- you will use.
Intense exercise increases fat use after the exercise is over. You use the readily available carbs during intense exercise, and then switch to fats during recovery. The body uses more fats as fuel after an intense workout than after an easy one.
Intense exercise increases post-exercise metabolism more than light exercise does. Run for an hour at 70-80 percent of maximum effort and you get an extra post-exercise calorie-burning bonus of nearly 100 calories.

Research Studies on Exercise Intensity and Fat Loss

Women are much more sophisticated about new weight loss programs than they used to be. They are less apt to fall for dramatic weight loss claims made by supermarket tabloids. Exercising intensely will help you lose fat faster than any other weight loss plan. This is supported by studies on animals and humans.
The benefits of intense exercise have been supported by a series of studies conducted for more than 10 years at Laval University in Canada. These results suggest that women who train intensely have more muscle and less fat than women who exercise at lower intensities. People exercising more intensely lost much more body fat, even though they exercised for less time than a moderately intensely training group.
Researchers from Duke University- led by Dr. Cris Slentz found similar results in a study published in January 2004. The 8-month study showed that people could lose weight through exercise alone without dieting (the average energy intake was slightly more than 2000 calories per day). People who exercised intensely lost much more fat than those who trained moderately. However, even moderate intensity exercise caused some fat loss.
A notable exception to these findings was a study published in the prestigious Journal of the American Medical Association in September of 2003 by researchers from the University of Pittsburgh, led by Dr. John Jakicic. They found that exercise duration or intensity had no effect on weight loss in obese women. Moderate exercise was just as effective as intense or long duration exercise. The major problem with the study was that the workouts were not supervised. Many women- particularly those who are severely overweight- feel uncomfortable training intensely unless they are closely supervised. Also, the study didn't measure changes in body fat- only weight and body mass index (determines if weight is proportional to height).
You use more fat as fuel when you exercise slowly but you lose more body fat when exercising intensely. High intensity training- particularly when using interval training (bouts of intense exercise interrupted by rest) increases release of fat from fat cells, fat use for fuel, and metabolic rate after exercise more than low- or moderate-intensity exercise, so you lose more body fat. Also, high-intensity exercise decreases appetite more than moderate or low intensity exercises. You're interested in the bottom line- does the program help you lose fat and make you look better in your clothes? Overwhelmingly, research studies shows that intense exercise is best for losing fat.

Losing Body Fat Through High Intensity Exercise

Train intensely - combining aerobics, interval training, and weight training- and you will lose weight and keep it off. Combine your program with a well-balanced diet. Do not follow a low carbohydrate diet, such as the Atkins or South Beach diets. They will not provide the carbs you need to train intensely. With this program, you won't have to worry about excess carbs: you will metabolize them rapidly during exercise and then chip away at your body fat for the rest of the day. As with any exercise program, begin conservatively and progress gradually. Below are some important principles for getting the most from an intense workout program.
Do 60-90 minutes of aerobic exercise at 60 to 85 percent of maximum effort, 3-5 days per week. This will burn about 500-1000 calories a day, which is enough to get rid of about a pound of fat per week if you train 5 days per week. That doesn't sound like a lot, but you will lose fat and not muscle. What's more, you will lose weight and it will stay off. Add a sensible diet to the equation and you will rid your body of excess fat before you know it.
Include Interval training in your workout: Interval training includes intense running (sprinting) interrupted by periods of rest or light exercise. If training on gym equipment, such as a treadmill or elliptical trainer, exercise intensely for one minute at near maximum intensity, rest for one minute, then repeat 6-20 times (depending on your fitness level). If training on an outdoor running track, begin by sprinting the straight-aways and walking the turns. As you increase fitness, increase the distance of your sprints to 200 meters and then 400 meters (rest 1-5 minutes between sprints). You will notice rapid increases in fitness and fat loss with this kind of training.
Train with weights at least two days per week: Weight training increases muscle mass that will give you a higher metabolic rate. More muscle mass means that you burn more calories during the day. Also, you will look fit if you have more muscle. Women do not usually build large bulky muscles from lifting weights, so train hard when you train.
Stretch after you workout, when the muscles are warm: Maintaining flexibility will help you prevent injury and maintain normal range of motion in the joints. Stretch after exercise during the cool-down period rather than before.
Eat a well-balanced diet: Eat a balanced diet containing a variety of foods. Include wholesome foods, such as fruits, vegetables, lean meats, whole grains, monounsaturated oils, nuts, and fish. Avoid simple sugars and saturated and trans fats. The Atkins type diet- high in protein and fats and low in carbohydrates- is not appropriate for this kind of exercise because you need carbs to train intensely. The Atkins diet works well for people who want to lose weight but are only moderately active.
Back off if you get injured: Intense training greatly increases the risk of overuse injuries. People who train intensely ride a thin edge between peak performance and injury because they push hard all the time. Back off on the program when your knees, Achilles tendons, hips, or back hurt. Take a few days off and then begin again at a lower intensity.

Train intensely and Lose Weight Fast

You can lose weight and look fit and healthy if you are willing to pay the price. Losing 10, 20, 30 pounds or more is no problem if you follow a few basic principles and stick with the program. More importantly, you can maintain your new weight. If you start today, one-year from now there will be a new you. You will be thinner, vibrant, healthier, and look terrific. The ball is in your court- promise to make fitness and diet a priority in your life and you will achieve the kind of body you want.

Sample High Intensity Exercise for Fast Fat Loss

(Build up to this program; Begin with walking and light weight training if you haven't been exercising. Increase the volume and intensity of your program gradually)
Monday: Aerobics (track or treadmill running, cycling, elliptical trainer, etc) 60-90 minutes at 60-85 percent of maximum effort.
Tuesday: Weight training (Do 1-3 sets of 10 repetitions for 8-10 exercises, emphasizing the major muscle groups of the body)
Wednesday: Interval training (Do six 200 meter sprints at 90 percent of maximum effort, resting three minutes between sprints; or ten one minute sprints on an elliptical trainer, with one minute rest between intervals); Aerobics, 45 minutes at 60-85 percent of maximum effort.
Thursday: Rest
Friday: Weight training (Do 1-3 sets of 10 repetitions for 8-10 exercises, emphasizing the major muscle groups of the body). Aerobics, 45 minutes at 60-85 percent of maximum effort.
Saturday: Interval training (Do six 200 meter sprints at 90 percent of maximum effort, resting three minutes between sprints; or ten one minute sprints on an elliptical trainer, with one minute rest between intervals); Aerobics, 45 minutes at 60-85 percent of maximum effort.
Sunday: Rest

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