Do you already know what is the reason why fasting cardio helps lose fat? For some people it may sound really crazy, because since we are kids, our parents always told us to have breakfast before doing anything, but this has a reason... It's because it relieves your blood glucose levels and goes down just like your insulin levels.

In the presence of insulin you don't burn fat! Because the body doesn't release fatty acids into the bloodstream to oxidize them as energy when insulin is high. Just 2 mg of carbohydrate per 100 ml is enough for the pancreas to secrete insulin.

Some may ask to themselves: Carbohydrate generates a large insulin response, but why not eat protein? Because, although the protein generates a minimum insulin response, the body will prefer it over fat as fuel. The body through gluconeogenesis can convert the protein into glucose and use it as fuel, and as you are fasting / insulin deficiency, any amount of protein, even if minimal, will trigger a gluconeogenesis.

Remember that body fat is a reserve of energy. It's gold for the body! Which will keep you alive in extreme emergency / famine. So when you are very close to your goal, or at a healthy weight and you are looking to tone up your body, losing these last pounds of fat is very difficult.

You don't wear out muscle mass if you do your cardio fasting correctly. Don't wait more than 15 minutes from the moment you wake up and don't do it at high intensity: Do it with an intensity that you can have a conversation that lasts 40 minutes, no more.

Right at the end of cardio, you can eat protein and a complex carb with a low glycemic index.

What you should never do is train with weights without having eaten, to do that you should eat protein and carbohydrates before.

If you have insulin resistance or you are hypotensive you shouldn't do cardio on an empty stomach.

The subject of fasting cardio is controversial. Many studies support it, but not everyone thinks it's okay to do it; but since each body is different, every person is free to follow what works best for them!