Weight Q&A – Burning Fat or Carbs


Weight Loss Q & A: What Fuel

We received a question from a website visitor this week, we decided to publish it here. Hope it helps!


Hi. just want to clarify, is it correct to say that if I jog at a reasonable pace, which I can still converse, then I’m burning fat. But if I really push myself to jog faster till I’m breathless, then I’m burning carbohydrates instead?


Yes, basically if we train at a lower intensity we tend to burn a higher percentage of fat.


We actually burn all 3 types of fuel (carbohydrates, fat & protein) all the time. The difference is the percentage or ratio of each fuel used. While resting or doing light work we burn a higher percentage of fat, the only problem is we don’t burn lots of energy when activity is easy or light. As we work harder we burn more energy but the percentage ratio shifts. This is where burning more stored body fat is dependent upon the individual and the intensity of effort which is right for that person.

As an example, ( lets ignore the protein energy used for simplicity reasons) we may burn 80% fat, 20% carbs when resting but only about 60 calories of energy is burned per hour. That equals about 48 calories of fat per hour.

While walking we could burn up to 180 calories per hour, but the ratio of energy burned may shift to 50%, 50%, that equates to 90 calories of fat burned. It means we’ll burn a greater volume of fat when exercising. That’s one reason why exercising to lose weight is crucial. However, there is a limit, if we exercise at too high intensity we may shift the ratio too far (90% carbohydrates 10% fats), so even though we may burn about 500 calories per hour, it equates to only 50 calories in fat. Another problem with very hard training is if we use up our carb stores quickly we tend to crave sugar to replenish the glycogen (stores of carbs in muscles), this may lead to overeating because the body craves more sugar in order to drive glycogen levels higher than previously. We also burn more protein for energy when exercising harder, again stimulating the appetite to drive you to eat more protein sources to aid recovery. Many protein sources like animal produce contain lots of fat and calories.

To complicate matters fitness plays a huge role. The fitter the person the harder they can work and still continue to burn a high degree of fat calories – it’s basically because their energy system is in top shape. That’s why you never see an overweight distance runner!!

The idea is to decide on the correct balance of intensity which is suits you. Train enough to burn sufficient calories without overdoing it. As you gain fitness over the months of regular training sessions you can gradually workout harder to burn off more calories taken from fat cells.

A qualified gym instructor can help assess your present fitness levels and estimate a range for the intensity level which is right for you to exercise within.

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