“Judge a man by his questions rather than his answers.” – Voltaire
«What is the exercise that burns the most calories»Is a frequently asked question, but it’s a bad question. It is based on the same simplistic logic as low-fat diets. As fat has more calories, let’s minimize its consumption so as not to gain weight. And as you know, it doesn’t work.
Of course calories matter, but they are only part of the story. Different types of calories (foods) produce different brain, hormonal and intestinal results.
Beyond calories, food is information for our body. If we talk about the output calories (exercise), the same thing happens.
If your training burns 500 calories, the result will be different depending on the impact produced by that energy expenditure:
- Have you burned more fat or more glycogen (during and after training)?
- What impact has it had on your hormones (testosterone, catecholamines, cortisol …)?
- What about protein synthesis?
- Have you built muscle or destroyed it?
- Have you generated EPOC effect to increase post-workout fat burning?
- What metabolic adaptations has this energy expenditure produced?
These are best questions that simply «How many calories have I burned?«
The goal of training is to maintain a healthy metabolism, build muscle, and impact hormones in a favorable way.
Assuming that your diet is under control, we will analyze below the benefits and drawbacks of the three main types of training and how to combine them to optimize your results.
Simplifying, we will talk about:
- Cardio or aerobic exercise.
- HIIT or high intensity interval training.
Cardio or aerobic training
The myth persists that medium intensity cardio is the best exercise for burning fat. This idea is mainly due to two factors:
1) The lower the intensity, the higher the percentage of fat used as fuel. By increasing the intensity, the body burns more glycogen.
2) The energy from fat (in absolute terms) is maximized with an intensity of 60-70%. It is the famous fat-burning zone that you will see on many cardio machines.
Although these ideas have some physiological validity, they are limited. They don’t let us see the global photo. Basing your training on long-term aerobic exercise has serious problems:
- Promotes muscle loss (study) in caloric deficit and the conversion of fast to slow fibers (review). The latter limits your strength, power, and hypertrophy gains.
- Excessive increase in cortisol (study). Maintaining a good testosterone: cortisol ratio is key to improving your physique. It’s the reason many marathoners can’t shed their belly fat.
- Requires prolonged sessions to be effective, especially as the body adjusts, burning fewer calories per minute invested.
- It’s boring. Yes, it is subjective, but for a reason the treadmill was originally invented as a torture machine :).
This is not to say that you stop doing cardio or that it is bad. Used well it has its benefits, but in the right proportion, as we will see later.
HIIT or High Intensity Interval Training
You already know the benefits of high intensity interval training:
- Increase catecholamines, facilitating the mobilization of fat (study), especially important when we talk about stubborn fat.
- Works the three energy systems simultaneously, also improving cardiovascular endurance (meta-analysis).
- Generates greater EPOC effect, burning more fat during the hours after training (study).
- Produces increased loss of body fat than an equivalent cardio (studio) program.
- Although some advise against high intensity training in those with cardiovascular problems, this meta-analysis in people with diseases cardiometabolic demonstrates a very significant improvement in cardiorespiratory fitness without negative effects.
- Takes less time. A 15-20 minute session is enough to generate a good stimulus. You spend fewer calories during training, but burn more fat overall (study).
As always, more is not better. High intensity is very effective, but it is also stressful on the central nervous system. Here I speak of concrete examples.
Prolonged low-calorie diets have two serious dangers:
- Slowing down of metabolism
- Muscle destruction.
Including strength training mitigates both risks, but not all strength training is equally effective.
When the main objective is to lose fat, many trainers recommend reducing the weight and increasing the number of repetitions, trying to increase the caloric expenditure. But if you are in caloric deficit it is better to do the opposite: increase the intensity (more weight) and decrease the repetitions.
When your body receives little energy, get rid of what you don’t use. Increasing the weight lifted sends a clear signal to your body: you need that muscle.
Resume: intensity is the key factor when it comes to maintaining muscle mass, not the number of repetitions.
Some example results:
- This study compared the results of the same hypocaloric diet in two similar groups, with the difference that one group only did cardio and the other only did weights. Those who did only cardio lost a little less fat but lost 4 kg more muscle. In addition, those who trained strength maintained their metabolism, while it was significantly reduced in those who only did cardio.
- Another study finds greater fat loss in different areas (lumbar and visceral) with strength training.
- A study in obese adolescents also shows greater fat loss in the group that trained only strength compared to that trained only cardio.
Strength training doesn’t necessarily require lifting weights. The muscle responds to a specific resistance, regardless of its source: a bench press or a push-up. The benefit of weights is that they make it easy to create progressive overload, but you can achieve something similar if you learn to master your body.
The perfect mix
Any type of training is better than doing nothing. But since our time is limited, we must maximize the impact of every minute invested. Endless cardio sessions burn a lot of calories, but they’re not the healthiest or most effective way to burn fat.
A recent meta-analysis, which reviewed more than 200 studies, perfectly sums up my opinion:
- Strength training (calisthenics and free weights) gave better results than cardio for fat loss and muscle development. Insulin levels also improved to a greater degree.
- Interval training produced better results than aerobic training.
And he concludes: «the focus of treatment should be on produce elevated metabolic stress rather than energy imbalance«.
Namely, let’s think more about the metabolic impact of our training and less about how many calories it burns. It is the best way to achieve results.
You should not exclude any type of training, they all contribute something, but use the appropriate dose of each. The following pyramid summarizes my general recommendation, the one that my programs follow, although of course it is customizable according to individual situations and objectives.
At the base I place strength training, with your own body or free weights (kettlebells, bar …). Three or four sessions a week is enough.
One or two weekly HIIT sessions, such as sprints, Tabatas etc.
You can complement with some cardio, either after the HIIT session or on a separate day. One benefit of combining HIIT + cardio is that HIIT is very effective at mobilizing fat and flushing glycogen. Some post cardio helps to oxidize mobilized fat, which will also be burned more easily with low glycogen stores. You can use some carbohydrate periodization strategy to optimize results.
As far as possible, don’t combine cardio and strength in the same sessionas you will limit strength gains.
Cardio is also interesting to modulate the caloric deficit. Although this deficit must come mainly from food (it is very difficult to achieve it with exercise), at a point it is dangerous to continue lowering calories. Adding more Strength or HIIT sessions can also be counterproductive – your muscles need to rest. At this point, some extra cardio can accelerate fat burning without the risk of overtraining or nutritional deficiencies.
And don’t forget the end goal: Fitness Global
We have focused on the impact of exercise on body recomposition (more muscle and less fat), but do not forget that, in addition to a beautiful body, we want a healthy and useful body, prepared for life.
Your training should help you:
- Improve your mobility. Move well before you move a lot.
- Develop all physical qualitiess in a balanced way. Use these tests for example.
- Save your life or that of others if necessary.
Train to live longer and better, not to burn calories.