HRM Fat Burn vs Fitness

that is exactly what i asked my trainer, and the answer was Yes, push yourself to your limit. the reason why is because when you are doing on a lower heart rate your body uses fat, but after you eat that fat goes back on. if you work out at a higher heart rate, your body uses glycogen which is stored in between your muscles, so when you eat instead of fat you put back the glycogen and build muscles, muscles that burn fat. you burn also when you are not pushing but not as fast as if you were pushing harder. it works for me. in a month or so i lost 14 lbs of fat and gained 4 lbs of muscles. you want the muscles for many reasons, just one being that your skin will get toned and not hang after you lose the weight. (if you have to lose a lot of weight)

hope this helps,

good luck

I, personally, find extensive amounts of exercise strictly in the fat burning zone tedious. I also struggle with the idea that I am doing less than what I could be doing to improve my overall performance for my next work out. That being said, there are any number of controlled, peer reviewed studies that condemn our ability to effectively mobilize stored adipose into fatty acids for the purpose of actual weight loss. We can move the, clearly, but ever so slowly, and more effectively when we are just at an overall calorie deficit. I think you are better off at the higher rate of calorie consumption that your 'fitness' zone implies, and burning other fuel sources that might simply have become fat if they had not be utilized for function.

I think Jillian Michaels explains it really well here:
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If you're looking to shed stubborn pounds, the rule of the game is to increase the intensity of your workouts. I want you to be working out at 85 percent of your maximum heart rate (MHR). However, you may have heard the "fat-burning zone" theory that encourages you to work out at just 70 to 75 percent of your MHR. The outdated assumption is that your body is drawing predominately on fat calories for energy — WRONG! It's completely misleading and it's time to lay the "fat-burning zone" myth to rest.

During physical training, your body has three possible sources of energy: carbs, fat, and protein. Protein is a last resort — of the three energy sources, your body is the most reluctant to draw on your protein stores.

Whether your body takes energy from glucose, which it gets from the breakdown of carbs, or fat depends on the intensity of your workout. Training at a high level of intensity forces your body to draw on carb calories for energy — they are a more efficient source of energy, and your body goes for its premium fuel when you're working hard. If you are training at a low level of intensity, your body doesn't need to be as efficient, so it will draw on a higher percentage of fat calories for fuel.

Sounds like low-intensity training would be more effective when it comes to losing fat, right? Wrong. These physiological facts are the ones that spawned the mistaken belief that low-intensity activity is better than high-intensity activity when it comes to burning fat and losing weight. These days we know that even though the ratio of fat-to-carb calories might be higher during low-intensity exercise, fewer calories are used up overall. High-intensity exercise burns the biggest number of calories.