The Fastest Way to Burn Body Fat

Numbers that don't lie when it comes to weight loss


Jan. 24, 2007 — -- Thank goodness the holidays are over, and the new year is here.

But are you finding that holiday celebrations have resulted in a new "you" as well?

As a personal trainer, I hear the same thing every year after the holidays: "Stefan, I gained fat over here," and "Stefan, I gained fat over there."

Be honest. Are you really surprised by the change in your body composition due to your calorie intake over the last few months?

You shouldn't be.

First, understand that your body's metabolism slows down 2 percent for each decade of your life after age 20. This means that your body burns calories more slowly with each passing year.

As a result, you should also be more careful with your calories as you get older. How much more careful? You can figure it out with the simple calculation below that will give you your basal metabolic rate, or BMR:

The number you end up with is your minimum daily calorie intake.

So say you are a 50-year-old man who would like to keep your weight at a trim 140 pounds. Here's how you would calculate your BMR:

Now keep in mind that some of you are more active than others. Hence, you should add on 180 calories per hour of housework (or if your house is already clean, feel free to come by and help me!), 650 calories per hour of cycling, 800 calories for every hour of running, and 1,200 calories per hour for cross-country skiing.

If you want to lose body fat, however, calorie control is only one side of the equation. The question you still need to ask is: "How do you burn the most calories and, best, the most fat calories?"

Interval training! Yes, you need to push yourself. You need to vary your training intensity between 65 percent of your total capacity to 85 percent and 95 percent. This approach will help you to lose the most calories from fat.

Stefan Aschan is a fitness consultant in New York City.

To understand the benefits of true interval training, let us look into three different training approaches for a 150-pound person who rides a stationary bike for 30 minutes:

This person who is exercising for 30 minutes at 65 percent will burn overall 82 calories, of which could be 41 from fat. This means that he or she will only be on the same speed and the same activity day in day out.

Think about it. Have you been in the gym and seen people day in, day out doing the same thing? And when you seen them two years later, does their body still look the same?

I have seen this many times, and I don't call this working out but rather flaking out. This training would fall in the aerobic, with oxygen, category -- also referred to as a low intensity workout.

If this same person is still exercising for 30 minutes but increases the intensity to 85 percent, this individual will burn overall 157 calories, of which could be 10 calories from fat.

This is the person who is sweating all over the treadmill, has water bottles staggered next to the bike and a second T-shirt to change into nearby. I have seen this many times as well, and I have not seen this person change either.

Yes, this individual has much stronger aerobic capacity. But again, if you take this person into a different environment, he or she will have difficulty performing on the same intensity level. This training would be without oxygen, in the anaerobic category -- also referred to as a medium intensity workout.

Now it gets interesting. When this person performs true interval training for 30 minutes and changes the intensity level of his or her workout from 65 percent to 95 percent and back to 65 percent, this person will burn 173 calories, of which 50 calories could be from fat.

Through this training, a person is able to train both energy systems, aerobic and anaerobic, to take advantage of the benefit of the most calorie-burning effects. This is true interval training and is referred to as a high intensity workout. These workouts are a killer, and if you don't feel like you are challenged and tired after those workouts you only performed a medium intensity workout.

Stefan Aschan is a fitness consultant in New York City.

The fact is that interval training burns more calories and fat, and it increases motivation, endurance and metabolism.

One of my favorite things about it is that it prevents boredom. Why else do individuals stop working out? And no, it's not the hassle of going to the gym. That has nothing to do with it. You can work out at your office, or even in your home, and reap the same benefits without a gym membership.

As I always say, take the common sense approach. If you do the same physical activity day in and day out, you will most likely perform a low intensity workout and therefore will not reap the benefits of weight loss that you are looking for. Neither will you continue reaching your best results when you don't change your nutritional intake.

Change your habits slowly. Start cutting back on excessive calories, and start implementing interval training as described above.

Stefan Aschan is a fitness consultant in New York City.

ABC News Live

ABC News Live

24/7 coverage of breaking news and live events