Cardio vs. HIIT vs. Strength Training: Which Workout Is Best for Burning Fat?

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What kind of exercise works best for weight loss and is it possible to wean off a bad diet?

I recently visited a gym that had a series of treadmills that had the text “Fat Burning Zone 60%” and “Cardio Zone 75%” clearly printed on the front. They reminded me of the days when some fitness professionals and companies were convinced that a certain style or intensity of training was the ideal way to burn maximum body fat. Part of this thinking continues to this day. It’s time to clear some of the confusion.

In-case-of-low-intensity cardiovascular exercises

The body uses different fuel sources during different training intensities. Low intensity activity, represented by the “60%” printed on the treadmill console (related to 60% of your maximum heart rate), uses fat as the main source of energy for fuel activity.

When the intensity increases, we can no longer use fat as a source of energy because the process of converting fat into a source that the body can use (glucose) is too slow. As a result, we are starting to rely more on carbohydrates, which can be processed and converted into glucose faster.

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Hence, the interpretation of these findings by many people at the time was that the key to weight loss was to exercise at the intensity that was using fat as the primary source of energy. It has also been argued that by exercising at lower intensity, it was possible to exercise longer, which increased overall energy expenditure. A somewhat logical and evidence-based conclusion, but one that does not address all aspects of weight loss. Gggggmyimg0

The case for high-intensity cardiovascular exercises

An alternative group of fitness professionals advocated a theory that uses evidence of “Excess Post-Exercise Oxygen Consumption” (EPOC) to suggest that we should exercise at a higher intensity. In layman’s terms, EPOC measures the increase in energy utilization after the end of a workout – it is known as “sports afterburn”, in which about five calories are burned for every liter of oxygen consumed.

In general, when you train at high intensity, you are using energy that is primarily derived from carbohydrate sources. High-intensity training creates an energy deficit that is greater than low-intensity training. So, if you do a high-intensity training session, the exercise makes an afterburn due to the energy deficit, which is primarily compensated for by the body fat reserves. This “bonus” period of calorie burning complements the energy used during exercise.

In addition, evidence suggests that an increase in metabolism can be observed. 48 hours after the first high duration bout, very high intensity exercises. Proponents found that this was the real miracle weapon, we had to train hard, sit on the couch and let the body “evaporate” for the next two days. Training styles that are able to utilize this acquired knowledge include HIIT training, MetCon (Metabolic Conditioning) and others, may base at least part of their popularity on this evidence.

Again, this seems to be a logical evidence-based approach, although it also neglects a critical component of the exercise in this hypothesis.


Increasing calorie burn for two days after exercising after intense cardiovascular exercise sounds pretty compelling to a lot of people. But our third group of fitness pros felt like the previous groups were easy to beat – and they didn’t even have to do cardio to do that. We know that skeletal muscle is not inert tissue that remains dormant until you decide to move.

Muscle is always metabolically active and while the energy used in resistance training is usually less than that used in cardiovascular training, it has been proven that more muscle mass means that the body uses an increased amount of energy for 24 hours a day , required seven days a week.

Hence, proponents would argue that an exercise that boosts metabolism around the clock would be the most compelling and best exercise method.

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The naked-numbers

Let’s look at the bare numbers – actual total calorie burn – is one way to gauge the effectiveness of all three of our zapping training styles. However, you will find that different studies lead to significant fluctuations in overall energy efficiency. We have selected studies that we think agree pretty well with most of the evidence. For more information on the quoted numbers and many others, search for Dr. Len Kravitz, who has published summaries and commentaries on the subject in many journals.

A study published in 1997 (Phelain et al.) compared the energy expenditure for two post-workout cardiovascular exercises. A low intensity workout and a high intensity workout that burned a total of 500 calories. Three hours after training the results were:

High intensity exercise:

  • 41 calories burned after exercise
  • 116 g total carbohydrate oxidation
  • 27.7 g total fat oxidation
  • A residual increased consumption of oxygen indicating further calorie expenditure, albeit at a slower rate

Low intensity exercise:

  • 22 calories burned after training
  • 85 g total carbohydrate oxidation
  • 36.9 g total fat oxidation
  • No increased oxygen consumption, no further calorie consumption

Donnelly et al. (2003) examined the EPOC of resistance circuit training with the following results:

Resistance training (weights):

  • This study does not cite actual exercise, but calorie consumption. Using Harvard Medical School guidelines for the prescribed program, the effort required during exercise could be estimated at approximately 200 calories and 58 calories after exercise.
  • Estimates of muscle metabolism are usually between 10-15 kcal / kg per day. At its best, by adding 2kg of muscle mass (a substantial amount), you can increase your resting metabolism by around 50 calories per day. So you can enjoy a single apple every day without feeling guilty about the metabolic activity of your extra muscle mass.

Put exercise-based-calorie-burning in context

Exercise and physical activity can have tremendous benefits for everyone, for a variety of physiological and psychological factors that would be too extensive for this article to cover. It should be an essential part of everyone’s everyday life. Gyms, health clubs, studios and fitness professionals should be paramount in helping people lead healthy and fulfilling lives.

However, those who are primarily interested in weight loss must recognize this important point regarding exercise: Any weight loss intervention based solely on exercise without regard to healthy eating and dietary management is doomed to failure. Here is why:

Total Daily Energy Expenditure (TDEE) is the term used to describe how many calories a person burns over a 24 hour period. TDEE has three main components. We have listed the average calorie percentage for the general population:

  1. Resting metabolic rate (RMR, 60-75% of all calorie burning processes)

RMR is the energy with which all normal body processes function. Your heart beats, your brain works. To demonstrate this in a caloric context, when they combine the energy expenditure of their heart, lungs, kidneys, brain and liver, their combined metabolic rate is between 15-40 times greater than their equivalent muscle weight.

  1. Thermal effect of physical activity (15-30% depending on a person’s level of activity).
  2. Thermal effect of feeding (approximately 10% of daily calorie burn).

As you can see, even if you are very physically active, you burn less than a third of your total daily calorie needs from exercise. For the vast majority of the population, there is one simple rule – you can’t work out a bad diet.

Nobody knows what “the best” is … and that’s fine

Assessing the effectiveness of any exercise style or combination is extremely difficult. Everyone is different and the variables are almost infinite. So it’s up to you yourself – find out what you enjoy and what is most important: what will bring the best results for you. With dedication, weight loss will be just one of the many benefits you can get for your endeavors.

Cardio vs. HIIT vs. Strength Training: Which Workout Is Best for Burning Fat?

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