In theory, cardio training on an empty stomach after a long night of hunger stimulates and spurs fat burning. If only that were true.
In 1999, Bill Phillips published the bestselling fitness book Body for Life, which promised a body transformation in 12 weeks.
In the chapter on cardio training, Phillips theorized that morning aerobic exercise on an empty stomach stimulates maximum fat burning.
The rest, as they say, is history. Since then, every Tom, Dick, or Harriett spun miles on a treadmill in the morning before a small serving of oatmeal went into their mouths.
The author argues his position as follows: prolonged lack of food leads to a decrease in blood sugar levels, which is accompanied by a decrease in glycogen stores (reserve carbohydrates). As a result, your body has no choice but to use fat rather than carbohydrates during exercise.
What’s more, low insulin levels during hunger promote fat burning and increase the availability of fatty acids as an energy source during a workout session.
The strategy has become popular among bodybuilders and representatives of allied sports disciplines, in which athletes tend to dry out to the maximum. After all, who doesn’t want to burn more calories without putting in the extra effort?
I’m sorry to say this, but all this pre-dawn workout on an empty stomach was a big mistake.
And that’s why.
Morning cardio and metabolism
To begin with, simply estimating the amount of fat calories burned during a workout session is a short-sighted strategy. Your metabolism does not take place in a vacuum.
In reality, the body continuously adjusts the proportion of fat and carbohydrates in energy generation, taking into account many factors. The more carbs you burn in a workout, the more fat you burn in the post-workout period, and vice versa.
Hence the question
What is the point of burning a little more fat calories during exercise, if literally in an hour the balance will swing towards more active utilization of carbohydrates?
Ultimately, there is no difference. You need to measure your fat utilization throughout the day – not over a couple of hours. This is the only way to get tangible dividends from the influence of this process on body composition.
But let’s say you’re a skeptic who thinks it’s best to burn more fat now rather than later. A tit in the hand is better than a pie in the sky, right? Not in our case.
Indeed, research provides compelling evidence that fasting cardio can increase fat loss during exercise when compared to post-meal cardio. The caveat is that this only happens at a very low intensity level. During moderate-to-heavy workouts, the body continues to break down significantly more fat compared to post-meal workouts.
Sounds good so far. Unfortunately, the increased levels of fat breakdown exceed your body’s ability to use excess fatty acids for fuel. In other words, excess fatty acids are circulating in your circulatory system, but you cannot use them to power working muscles.
After all, all of these fatty acids are packaged into triglycerides after exercise and sent back to fat cells. It turns out that you have made an extra way … only to return to the starting point.