Q: when I was doing cardio I kept my heart rate at about 125 beats/minute for 50 minutes but It was no longer helping me lose weight. Since I started doing cardio at my training heart rate (Between 140-155) I have lost 4.4 pounds in 5 days! And I was doing it for only 30 minutes. the total calories that I burn when I'am working out at the training heart rate level was no more than when i was doing 50 minutes at a 125.So how come I'm losing weight when these two different workouts yield the same calories?

A: Congrats on your weight loss and great job not giving up on your program just because results seemed to have stopped! The thing you have to keep in mind is that your weight loss will almost always come in spurts and only a small fraction of those 4.4 pounds was fat. Let me explain why...

The reason for rapid spurts in weight loss (or weight gain for that matter) is almost always due to diet and digestive tract changes. A small change in your diet can drop your weight by a few pounds very quickly -- it's not a true fat loss, but it's a change in water weight. Your body retains a lot of water in your digestive tract and starchy foods keep more water than non-starchy. So, for example if you go from eating a lot of bread and pasta and potatoes to eating just salad greens, then your weight will drop a few pounds within just a day or two. Other changes like eating a lot or a little in a day, drinking coffee and alcohol can bring about similar temporary drops or gains in weight.

Even if your diet stays absolutely constant (which is very unlikely), your system can still sometimes get a little backed up and then suddenly empty out quickly causing similar effect.

Finally, unless you always weigh yourself first thing in the morning on an empty stomach, your measurements are not going to be very reliable. I always always recommend that you weigh yourself without clothes right after getting up in them morning and using the restroom if needed. Don't eat or drink anything before weighing yourself.

Because of these spurts of weight loss (and gain as well), I usually recommend that you don't count the first few days when you go on a new diet and that after those first few days you keep track of your weight and take averages every 2-3 weeks. Averages over time give you a truer picture of what's going on instead of jumps up and down from day to day.

So how much of that 4.4 pounds of weight loss for you was true fat loss? Assuming you did intensive cardio for 1 hour each one of those 5 days, the most fat you could've burned would be about 1 pound (one hour of intensive cardio will burn around 700 calories. 5 days * 700 calories/day = 3500 calories or about 1 pound of fat's worth). More likely though, it burned both fat and muscle in a ratio that would depend on your diet and other physical activity you do.

That fact that you're losing both fat and muscle is another thing well worth discussing... ANY form of weight loss for most people, perhaps excepting those who are just starting out and are very out of shape or very overweight, will cause loss of both fat and muscle. This not widely known and appreciated but is very very important. Fat loss is great! Extra fat is what makes you look bulky or flabby and it's also what can cause a host of health problems. By all means you want to lose fat. Muscle loss however is a whole other matter. Muscle mass is very important for your strength and endurance and becomes absolutely crucial at old age. Healthy muscle mass at old age may well be the main thing that allows you to lead a full life well into your 70s and 80s and even beyond! BUT, even if you could care less what happens in your old age, your muscle mass is your biggest ally in BURNING FAT now!

Why? Because muscle is a metabolically active tissue constantly being rebuilt and repaired which uses up energy and burns fat! Fat tissue, on the other hand, is metabolically dead -- it doesn't require any energy to maintain itself. The less muscle you have, the less fat you'll burn -- it's that simple. When you lose weight, your body is put in a situation where it has to decide between burning muscle or fat for energy (both can be used for energy by your body). It will almost always burn both because your body voluntarily does not want to lose weight! So it reluctantly burns fat because that's what fat is there for -- to keep the body going through tough times! But it also burns muscle because by burning muscle it lowers its future metabolic needs and can reduce energy requirements to keep itself going without losing weight.

By now it should be clear that you want to force your body into burning as much fat and as little muscle as possible during weight loss. And that's where a good diet and a good training program comes in. A good training program should encourage your body to keep the muscle. The way to do it is by using the muscle to its maximum potential. The best way of doing it is heavy whole-body weight training -- it sends the signal to your body that says to keep the muscle because it's being used! Not only does heavy weight training send that signal, it also heavily damages your muscles forcing your body to spend a lot of energy repairing them and thus burning even more fat! If not weight lifting, then the next best thing is playing sports that require a lot of maximal exertion -- football (on nearly every play), soccer (sprints racing to the ball), etc. If you don't do weight training or sports, then the next best thing is to do as intensive cardio as possible -- again, telling your body that you need all the muscle you have. So the fact that you upped your cardio intensity is a good thing!

Finally, don't forget about the diet! It is equally important to continue stimulating fat-burning. I describe how to put together a good fat-burning diet in my Nutrition article.

So after all that my advice to you is: 1) think how you can improve your diet based on my article, 2) strongly consider doing weight training, and 3) if you decide you don't want to weight train, then continue doing your higher intensity cardio.