As a life-long athlete, I’ve never had the sort of intimate relationship with the fat battle that some people have, but a woman named Lisa brought reality home to me with her experience. “I was 135 pounds before the birth of my first daughter, but 210 pounds after the birth of my second. One day, my husband came home with a heart rate monitor. I’d heard about Sally Edwards and her Heart Zones Training system and decided to give it a try. I bounded into the Z2 zone and hung out there for one and one-half years, ate everything I wanted but limited my dietary fat intake to 30 grams a day and the fat slowly melted. I have maintained 135 pounds ever since.” Lisa sustained a healthy weight loss amounting to about one pound per week.
WHAT IT DOES
The Z2 Temperate zone is so-called for a simple reason: It’s a moderate and comfortable zone. In zone 2, approximately 70%-85% of all of the calories that are burned come from fat and the rest from carbohydrates (CHO). However, unlike the 4-6 calories or so per minute you can expect to burn in the Healthy Heart zone, in the Temperate zone an average person will burn about 6-10 calories per minute! So, in ten minutes of exercise, depending on your weight and other factors, you’ll burn about 100 calories. Approximately 85 calories will be from fat in your diet or your own body releasing it’s stored fat. This blend of fat and CHO, carbohydrates, changes based on your diet, current fitness level, genetics, amount of exercise, etc.)
As you continue to train into the higher zones, you burn more calories, but you also burn proportionately less fat as a percentage of your total calories. Is it better to burn more “total” calories during higher heart zone workouts, or to burn a higher “percentage” of your calories as fat calo-ries? The answer is – it depends. It is individual, depending totally on your fitness level and your goals. If you’re already in shape, it’s best to burn total calories; if you are on your way to getting fit, it’s better to burn fat calories. If you’re in great shape, you don’t need to hang out in the low zones, because you are fit not fat. If you are fat and not fit, this is the place for you.
By exercising in the temperate zone, you double your health rewards because you burn more fat and, at the same time, gain muscle mass. Consequently you have more muscle available to burn even more fat as your resting metabolic rate (RMR) increases. In other words, the more muscle mass you have, the more calories you burn just sitting still.
And, when you get into relatively good shape, you can hang out in zone 2 for a longer period of time – it can be a recovery zone or a long, slow endurance zone. If you use the Temperate zone for either purpose, then the blend of fuels your body burns becomes even more in your favor. With longer training sessions, more than 60 minutes in duration, your body begins to run out of the readily available carbohydrates in your system and relies even more on your body’s stored fat. In the first few minutes of exercise, there is a tendency for the muscles to grab carbohydrates for fuel because they are readily available and don’t have to be mobilized.
This makes sense because when you first start up, you’re body’s looking for whatever it can get its hands on to stuff into the furnace. The longer the exercise duration, the more body fat can be broken down and shuttled out to the muscles via the bloodstream. That’s what’s so great about long, slow training – it increases your fat mobilization.
Glycogen, or stored carbohydrates in the muscles, is depleted with long exercise sessions while fat can remain in abundance.
HOW IT DOES IT
The floor for the Temperate zone is 60% maximum heart rate, just above the Healthy Heart zone. The ceiling of the Z2 Temperate zone is 70% maximum heart rate, just below the Aerobic zone. As you exercise in the Temperate zone you realize even more of the health benefits that training anaerobically, that is, “without oxygen.” At these intensities, carbohydrates are burned, not fat.
These three steps in the process of fat loss – the release of fat from cells, the transportation of fat to the muscles, and the higher concentration of fatty acids, combined with the availability of oxygen with which to burn the fat, happen far and away the most efficiently in the moderate intensities of the Temperate zone. In other words, hanging out in the Temperate zone allows you to open up your fat cells and let the fat come out.
GETTING BETTER ALL THE TIME
The benefits of exercising in the Temperate Z2 zone go on and on. Studies show that those who work out at low heart rates burn more fat, even when they are not in the midst of a training session, than do those who don’t exercise. Training teaches the metabolic processes how to preferentially pick fat over sugar.
How does this happen? Remember when we talked about the training response in the last chapter? Working out in the Temperate zone causes these kinds of extended changes in your body’s structure or function.
Specifically, the amount of stored fat you can burn is related to the rate at which you can supply fat to your muscles. When you increase the rate, you increase the percentage of fat burned. That’s what training in the Temperate zone does – the more you train in the Temperate zone, the more efficient your body becomes at using fat for energy since, with exercise, there is an overall increase in the activity of the fat-burning enzymes. This makes more fatty acids available, leading to an increase in the availability of fat as the primary energy source. There is another factor that determines the rate at which you can supply free fatty acids to be burned: the amount of blood flow to the muscle. When you engage in regular training, you increase the blood transport system’s ability to deliver blood by increasing the number of capillaries surrounding the muscle fibers, so more blood flows to your muscles. Training in the Temperate zone allows you to increase the amount of free fatty acids released out of your cells and into your bloodstream as well as to increase the amount of blood flow to your muscles.
Also, by training in the Temperate zone, you substantially increase the number of mitochondria in each muscle fibre. Since fat combustion takes place in the mitochondria, the more you have of these small energy factories, the more fat calories you can burn. Next, the size of the mitochondria increase with exercise. With bigger energy factories – mitochondria – you can combust even more fat calories. Research has shown that mitochondria get about 35% bigger with training, while there can be as much as a 15% increase in the quantity of mitochondria.
The mitochondrial enzymes’ activity increases, too. Increasing this activity increases the mitochondria’s efficiency and, thus, the muscles’ aerobic capacity (your ability to utilize oxygen). With an increase in the number, the size, and the activity of the mitochondria, the Fat Burner is well-equipped to release, transport, and burn more and more fat as a source of energy. As you hang out in the different zones, another one of your body’s training responses is to increase the amount of your muscle tissue or lean body mass. You want this. The more muscle mass you have, the more calories you burn at rest and your resting metabolic rate, the amount of calories you burn by just being alive, increases.
None of these changes happen overnight, so don’t expect to start a Heart Zones Training program and see improvements on your second day. When you add a weight loss component to your training there usually isn’t immediate weight loss. This is normal. We often think we can “beat the system.” We can’t. Heart Zones Training works within the system, optimizing the way the body works.
At some point as you increase the intensity of your exercise, your muscles shift to using a higher percentage of carbohydrates than fats. This intensity level is called the “cross-over point.” That is, as your heart rate increases, your metabolic response crosses over from using mostly fat as the energy source to predominantly CHO. One of the definitions of fitness is to change this crossover point to a higher heart rate. As you get fitter, you burn more fat calories at lower heart rate numbers than when you are less fit.
In the old school, coaches preached the philosophy of “LSD” workouts. Now, before you start thinking that all those runners out there in the ‘70s were so stoned out of their minds that it was a miracle they weren’t tripping over their own feet, let me clarify. To us, “LSD” stood for “Long, Slow Distances.” We did twenty a day’ers – twenty miles a day of running – as frequent workouts. We were convinced that the longer we ran, the more fat we would burn (which is generally true) and that this was one of the tracks of the road to true runners’ high. We ran and ran and ran for years and years and years. But, as students of both our experience and of ongoing scientific research, we began to cut back, run fewer miles, and set more personal bests. We learned the Heart Zones Training lesson, that the quality could be more important than the quantity of our exercise.
Today we’ve entered the era of SSDs – short, slow distances. That’s really what the Temperate zone is, at least in the beginning. The results are huge on the health continuum as well as in the mind.
So, how do you put the Z2 into practice? Do what a friend of mine named Juanita does four times a week – twenty-aday’ers but minutes not miles. She loves a variety of cross-training, so in the summer she swims one day, circuit trains in gym for one, bikes another, and walk-runs a fourth – each for twenty minutes, and each in the Temperate zone. In the winter, one day a week she circuit trains for 20 minutes, the next she sport snowshoes for 20 minutes, the third she cross-country skis, and on the fourth she uses a stair-stepper or treadmill machine. Twenty minutes, four times a week is enough to melt the fat away, so long as it’s twenty minutes in the Temperate zone.
Each time, fitness enthusiast Juanita burns fat calories as her primary fuel source, even though she doesn’t burn as many total calories as if she were in the Aerobic zone. And she enjoys the workout because it’s fun and not painful. Because of the variety, she keeps her motivation and interest high. Each time she knows that she is investing in her health – the most important thing she has in her life.
Remember, though, training in the Temperate zone is only half of the fat-loss game plan. If you eat a high fat diet, then your fat cells are competing with what you just ate as the source of fat for energy. Muscle fibers prefer dietary fat over stored body fat, after all.