That's great! And it is probably the reason that you are reading this article, hoping to lose weight while or through exercising. But let me first dash your hopes: you probably won’t. The scientific ‘British Journal of Sports Medicine’ once put it rather succinctly: “You cannot outrun a bad diet”. Your weight, or rather your overweight is quite simply the result of the difference between your calorie intake and your calorie use. It would seem logical that when you increase your energy use by exercising, you will automatically lose weight. Unfortunately, it’s not that simple. To explain why this is the case, we first need to focus on the different types of energy consumption.

Do I need to burn fat to lose weight?

Your body relies on three types of energy sources; carbohydrates, fat and protein. Burning the latter is not a good idea, because those proteins are essential for muscle recovery. The body knows this and only starts using protein after the other two sources have run out. You might have experienced this once after a very, very long and hard ride, the tell tale sign is the (horrible) smell of ammonia. The first option, carbs, is the most efficient one. But the problem with carbs is that the body's storage ability is not that big. An untrained body has about 300 to 400 grams of carbs stored in the liver and muscles while a trained individual can double this capacity. The higher the intensity of a training session gets, the more your body relies on burning carbs. When you exercise at your FTP or threshold heart rate you will exhaust this storage in about an hour, while the maximum carbs intake is 60-90 grams per hour. By the way, at lower intensities, some carbs are also still being used as energy. For example to keep your brain and other vital organs functioning.

How to burn fat?

The body's real energy bomb is fat. The availability of it is nearly infinite, even when your body fat percentage is quite low and everybody else thinks you are really skinny! The only problem with fat is that the body needs a lot of oxygen to turn that fat into fuel. Exercising at a high intensity, your body depends almost exclusively on carbs, but at a low intensity your body burns mostly fat. If you want to lose weight then exercising at this low intensity is the only way to do it. Burning carbs, you lose very little weight because your body will be craving to replenish that carb storage in the liver and muscles after the training. This is a natural process that cannot be altered or tricked. Take also into account that the better your stamina gets, the higher the training intensity will be at which your body can still rely on burning fat. So especially for those who start exercising with the idea of losing weight, the intensity should be really low to actually burn fat. Even so low that it doesn’t feel like exercising. And then still, the training sessions should also really be very long to have any effect.

Don't forget the calories!

Here we have addressed the fact why you probably don’t lose much weight when you start exercising. But there is more. If you exercise you cannot just add those burned calories to the normal energy expenditure. Studies show that the basic metabolism of people who exercise is lower. It seems that when we have done a workout, we have a tendency to reward ourselves by being less active and even sin by having not that great food. By now you are probably thinking that the above does not apply for you. You are probably someone who will beat the statistics and start to exercise at exactly that low enough intensity and long enough duration, while also tackling the mental hurdles.

Keep it fun.

Even then losing weight through exercising just doesn’t make sense. It’s like eating soup with a teaspoon. It can work but it takes ages and you probably don’t even enjoy the soup. If you still want to have fun exercising, extremely low intensity and monotonously long sessions are not the way to do it. Having fun with what you do is actually one of the strongest and even scientifically proven incentives to stick to an exercise regime. On top of that, it would be a pity to exercise only at a low intensity because you will miss out on all the other benefits to your stamina of exercising at a higher intensity.

So if you want to lose weight you need to change what and how much you eat. If you’re struggling with your weight, more often than not there is something wrong with your diet and/or lifestyle. So start exercising because of all the associated benefits and the fun of it, but also as part of a lifestyle change. Don’t just try to eat the soup with a teaspoon although you will probably lose weight by doing so.