I normally try to focus here on ideas related to motivation and the mental aspects of fitness and weight management, but this entry is going to talk about some info you can use to make sure you're getting the most out of your fat burning potential.
We all know that getting fit and healthy is more about losing fat than about making the number on the scale go down. In fact, most of the things people do to get dramatic or fast results on the scale either don't have much to do with losing fat, or may actually make it harder by forcing their bodies to cannabalize muscle and organ tissue--the same tissues that actually use the most fat as fuel.
So, if you want to be in the business of burning fat, it pays to know as much as you can about how and when your body actually does that.
Fat is your body's "default" energy source. It's the preferred fuel source when nothing special is going on, while you're at rest or doing fairly light activity. You're never burning just fat, because your body can't burn fat unless some glucose (sugar) is available, along with oxygen. At very low intensity levels (like while you’re sitting in front of your computer reading this) you’re body might be getting 80% or even more of the energy it’s using from the fat you have stored in your body.
The problem, from a weight loss perspective, is that you’re not burning up very much total energy (calories) when you're at rest, so 80% of this small number of calories doesn’t amount to much actual fat burning. At the other extreme (like when you’re running a 100 yard dash) you’re burning tons of calories per minute, but virtually no fat, just carbs (glucose). That high intensity level is great for creating a calorie deficit, but by itself, it may not be the best way to maximize fat loss, mainly because you can't maintain that level of intensity for very long.
Somewhere in between these two extremes there will be an ideal mix of activites and intensity levels that produces just the right combination of total calories burned and total fat burned. Finding your ideal mix is the name of the game when it comes to losing fat. And this is not
the same thing as trying to create the largest calorie deficit you possibly can. If you think about it for a minute, you can see that there's a limit on how much fat your body can use in a day, because this is determined mainly by the intensity of your activity. If your calorie deficit is larger than the amount of fat you can burn, you are going to lose some muscle and organ tissue.
Fat Burning Facts You Need to Know
Your Aerobic Threshold and your heart rate.
There is an actual “point of maximum fat burning” at which your exercise intensity and your body’s ability to use fat as fuel combine to generate the largest amount of fat burned per minute of time spent. That point is called your aerobic threshold. This point differs for each individual based on several factors, including your fitness level and how efficient you are at doing that activity.
Your exact aerobic threshold can be determined by a procedure that measures and analyzes your exhaled breath while you exercise at different intensity levels. You can probably get this done for around $150-200 at a college with a graduate level exercise science program, or at many athletic training programs or sports medicine clinics. It will also tell you what heart rate corresponds to your maximum fat burning point.
Fortunately, though, you don’t have to know exactly what your personal aerobic threshold is in order to use this approach effectively for weight loss. The amount of total fat burned shifts gradually upward until you get to your aerobic threshold, at which point it starts declining fairly rapidly until you get to your anaerobic threshold--the point at which your heart and lungs can no longer deliver enough oxygen to burn fat, and lactic acid starts builing up faster than it can be removed, causing your muscles to "burn" and eventually, forcing you to stop or slow down your activity.
For most people who are neither very unfit nor extremely fit, you’ll be working close to your aerobic threshold, and burning the most fat, when your heart rate is between 65-75% of your estimated maximum heart rate.
Now, I hope you’re not sitting there thinking something like: “Oh, good, now I can drop those awful high intensity interval training workouts, and focus on the easy stuff.” The idea here is not to downgrade all your high intensity workouts into lower intensity workouts. You do not want to decrease your total calorie burning, or miss out on the health and fitness benefits of including some high intensity exercise in your weekly schedule. The goal here is to simply expand your focus so that you’re thinking about burning fat as much as you are about burning calories. Your ideal plan will still include a mix of high and low intensity exercise, strength training, and as much other activity as you can manage to include in your life.
You’ll need to figure out for yourself what kinds of activities keep your heart rate in the “aerobic threshold zone” of 65-75% of your maximum heart rate. If you haven’t done it already, this might be a good time to think about getting a heart rate monitor, or really familiarizing yourself with the Rating of Perceived Exertion scale. For many people, though, it will probably be as simple as adding a little uphill to the daily walk or bike ride.
Timing your meals to maximize fat burning.
Another thing you can do to enhance your fat burning potential during your moderate exercise sessions is to avoid eating anything (and especially fast-digesting carbs) for an hour or two before your workout. Eating carbohydrates stimulates your body to release insulin into your bloodstream, which enables your body to get glucose into your cells where it is used as fuel. Insulin also inhibits use of body fat as fuel a little, which is fine when you’re working at high intensity levels that don’t burn much fat anyway—your body will do the fat burning when it’s making up for your calorie deficit after the exercise. But you won’t need as much glucose for a lower intensity workout, and minimizing the insulin response right before exercise will allow your body to take a little more fat out of storage and get it to your active muscles. If you can handle the amount of aerobic threshold exercise you have planned without a pre-workout meal, do that. If you need something to eat to provide energy or keep your blood sugar levels from dropping too much, try eating a snack that includes protein and complex carbs an hour or so before your workout. But don't risk getting dizzy or having a blood sugar crash just for the sake of burning a few more fat calories.
If you're one of those lucky people who have time for lots of physical activity in your day, a great way to maximize fat burning and fitness is to include both a fairly short, high intensity workout and a longer, aerobic threshold workout.
A final thing that's important to keep in mind is that all activity helps burn fat. Many studies have shown that the difference between people who find it easy to maintain their weight and those who tend to gain easily is often not in how much they eat--it's at least partially in how active they are even when "at rest." Your hollow legged friends may seem that way mainly because they do a lot of fidgeting and moving around even when they're sitting in front of the TV.
So, don't just sit there. Fidget.