This is a very contentious area. Mr. Weightless will only tell simple truth, so below is information that has been proven to be true, but final judgment is yours.

Slow and Steady Wins Race...

Slow and steady exercise that raises your heart rate a significant amount, but that still allows you to breathe without struggling for at least 20 minutes will encourage fat loss. This is called aerobic exercise. The term aerobic means "with air", meaning that your muscles are burning sugar and fat in presence of oxygen. To be able to burn calories in presence of oxygen, you have to be taking regular breaths, so activity you're doing must be a moderate pace, at most. For many people who are overweight, this can mean simply a fast walk. For many athletes, this may be a quick jog. It doesn't matter where you are along spectrum as long as your heart rate is raised and you can breathe normally or carry on a conversation.

Why 20 minutes? At first, your body will only burn blood-sugar because it is readily available. If you keep going long enough, your body realizes that blood-sugar won't be enough, so it starts burning fat as well. If you stop exercising before this happens, then your body will simply be tired and you will feel hungry because your blood-sugar will be low (see my article on Satiety, click here). Your body wants to retain fat and avoid burning it. This is a survival mechanism... read my article on Adaptation that you can find on my website.

...Or Does Maximum Intensity?

There is another school of thought that has had similar success with just as much good theory behind it. Vigorous exercise for 10-15 minutes will burn just as many calories from your blood-sugar as a longer duration exercise, but it will also raise your metabolism for many hours afterwards. In other words, you won't burn fat during your workout, but you will slowly burn fat for a period of time after finishing. This method has been shown to have more dramatic effects on lowering body-fat than low-intensity exercise described above. This is anaerobic exercise, meaning "without air". You'll be going fast enough that your breathing won't be enough to fuel calorie burning. Carbohydrates (blood sugar) will burn without oxygen, which leads to creation of lactic acid. This is what accumulates in your muscles, and makes them feel like they're burning.

However, there are serious drawbacks to this method, which make it difficult to recommend this strategy exclusively. Before embracing high-intensity mindset, read below.

First, if a person is just starting a program, they risk serious injury if they try to exercise too vigorously. Knees, hips and ankle joints are very common injury sites, and muscle cramping can be very painful even if it is short-lived. Don't exercise at your peak intensity until you're used to exercising!

When average person hears word “ephedra” they generally think of two things: “weight loss” and “banned.” The millions of people who have safely used ephedra to burn fat and lose weight were devastated when U.S. ephedra ban was imposed in early 2004. The FDA was claiming a high death rate attributed to use (or misuse) of ephedra and ephedrine (the main “active” ingredient in ephedra plant). However, further research showed that only five of these deaths could be attributed to ephedra use, so ban was lifted. To put number of adverse events into perspective, consider that over 12 million people reportedly used ephedra during 1999.