The Cardio Fat Loss Plan

Start a conversation about cardio, and you might as well be talking politics and religion. After all, no matter what you say, someone will be pissed off and likely challenge your every thought.

On one end of the spectrum, you have the “cardio haters.” You know them as the people that believe cardio is a complete waste of time and will kill your muscles and your body. (I even saw one article go as far to say it will actually kill you. That’s a bit much.) Then there are the “cardio lovers,” they’re typically distance runners and mileage junkies that pound the pavement—or the treadmill—and feel that running is the best form of exercise. (Expect rampant “Born to Run” references.)

The truth always depends on the context. Instead of asking if cardio is good (it is, and in many forms), you should be asking a different question:

For fat loss, HIIT workouts will definitely have more bang for you buck, but lower intensity cardio still plays an important role for your health and training.

“Why am I doing cardio?”

Maybe more appropriately, “What do I hope to achieve by running?” Or what most people really want to know: will cardio speed fat loss? 

If you’re looking to burn the most fat with an efficient approach, let this article be your guide. -AB

The Cardio Fat Loss Plan

By Chris and Eric Martinez

Cardio always appears to be the solution to burning fat. That’s what runners will tell you.

Talk to someone that lifts weights and they’ll tell you to move those weights faster or to perform intense intervals.

It might sound simple, but that sums up the great cardio debate: The slower, longer steady-state approach (sometimes referred to by researchers and internet scientists as LISS) versus the shorter, high-intensity plans (HIIT).

So what’s the right cardio for you? The answer isn’t necessarily as black and white as you might think, but in less than 5 minutes we can teach you a more efficient way to burn the most fat.

The Difference between HIIT & LISS

HIIT stands for High-Intensity Interval Training, which consists of short sprint intervals coupled with low-moderate intensity work. An example of this would be a 10 to 30-second sprint followed by a 3 to 5-minute steady pace walk to cool down and bring your heart rate back to normal and then repeating it.

LISS stands for Low-Intensity Steady State cardio, which consists of low-to-moderate intensity work. An example would be walking on the treadmill or riding the bike while holding a conversation. (We tend to see a lot of this at commercial gyms.)

The Burn: What You Really Want

We love science and as complicated as it might seem sometimes, researchers have made it increasingly easy for us to figure out exactly how we should be spending our time in the gym. You see, two tests, in particular, paint an interesting picture: lactate threshold (LT) and anaerobic threshold (AT). The LT and AT are extremely powerful predictors of performance in aerobic exercise (cardio).

There are 2 ways your muscles can burn glucose (blood sugars): aerobic (with air) and anaerobic (without air). For example, long bouts of LISS cardio are considered aerobic work, while weight training or HIIT cardio can be classified as anaerobic work.

The AT and LT are a great test for HIIT and LIIS cardio because it provides a great predictor of which type of work produce ATP. (Adenosine Triphosphate) It’s best to think of ATP as a quick burst of energy whenever you contract your muscles. (For example, every time you do a bicep curl you receive a surge of ATP).

HIIT produces better changes in exercise capacity as opposed to LISS cardio. High-intensity training will hit the AT and LT, and that’s what causes your body to experience metabolic changes. When you are doing LISS, you are considered below the AT and LT.

Translation: When performing HIIT style workouts you’re improving your metabolism. And when that happens you can expect more fat loss over time.

Changing Your Metabolism with Cardio

Even though genetics play an important role, you can “convince” your metabolic to change…if you force it. The easiest way is to increase muscle mass and your muscle’s oxidative capacity. Your muscles have these energy-producing units called ‘mitochondria’ and this is where ATP is made and fats are burned.

The more mitochondria you have and the more active they are the greater oxidative capacity you have for fat loss. HIIT increases mitochondrial capacity and you actually increase the number of mitochondria you produce.

Studies show that you achieve greater fat loss through high-intensity training because of the increase in oxidative capacity. Whereas with LISS you’re only burning calories at that precise moment, there’s no 24-hour energy expenditure (boost in metabolism) and it hurts you down the line because your body adjusts to it and you end up needing more and more to lose fat.

In other words, when you crank up the intensity you’re actually changing your muscle’s metabolism, thereby boosting your caloric burn because you increase the mitochondria density of your muscles.

While it sounds great on paper, here’s what you must realize: HIIT isn’t a walk in the park. (Literally.) You must make your body a little uncomfortable (but not painful) because you’re pushing your body to an extreme.

Slow Cardio Is Not Bad. It’s Misunderstood

Your body is very adaptive. We tend to see a lot of people doing hours and hours a week of LISS and according to calculations they should be losing pounds, but they don’t see changes because their metabolism adjusts to low-intensity exercise.

If you do LISS all the time, you’re basically trading calories in and calories out and you can cut these same calories through diet and still get the same effects. Let’s put it another way: Say you burn 200 calories during 30 minutes of work on the treadmill.

That’s a good workout, but the caloric deficit is just 200 calories. If you wanted, you could cut out 200 calories through carbs or fat and basically get the same effect as opposed to receiving a 24-hour metabolic boost through HIIT cardio.

A study conducted by Wilson et al. from the University of Tampa, FL, found that when you add in LISS you experience a temporary boost in weight loss. Subjects lost a couple of pounds the first week and after that, they lost nothing. This happened because their metabolism completely adjusted and that became their new set point to what they had to do just to maintain.

Maybe, more importantly, the research suggested that steady-state cardio with a low-calorie diet is not ideal for fat loss and could cause muscle loss.

You see, with lower intensity cardio your metabolism becomes adjusted to the pace and you constantly have to do more and more to receive similar results. In that way, it’s almost like a drug. Your body creates tolerance and you need higher and higher doses just to create the same effect.

Even worse? Oftentimes those people doing cardio to lose fat are also on a low-calorie, low-carb diet. When this happens, your body doesn’t have much stored glycogen (the carbs you store in your muscles) so your body goes searching for other sources of energy.

One of those energizers? Protein. And when that happens, you might start tapping into your muscle stores, which isn’t exactly what you want to do on a fat loss plan.  Just to prove the point, in the same study by Wilson et al, people who did slow steady-state cardio lost more muscle than those who performed the high-intensity intervals.

Creating Your Cardio Fat Loss Plan

What does it all mean? On the surface, it might appear that you should only do high-intensity cardio, but that’s not completely accurate.

For fat loss, HIIT workouts will definitely have more bang for your buck, but lower intensity cardio also plays an important role in developing your different energy systems, helping with cardiac health, and even promoting recovery from sore muscles. We’re big believers in combining both high and low-intensity cardio. Here’s a checklist of why:

  • You can’t do HIIT 5 to 6 days a week because eventually it will have a negative impact on your weight training and it’s too much stress on your central nervous system. Imagine driving your cardio at its max speed every day. The engine would burn out. Your body works in similar ways.
  • Many people have legitimate orthopedic, cardiac, and even psychological reasons to avoid HIIT, so LISS is their only option
  • HIIT could be dangerous if not used right and could lead to injury

There’s also another X-factor: your mind.

Some people have trouble pushing themselves to the max, and thus HIIT cardio becomes something that’s not enjoyable and not performed. It might sound like an excuse, but for anyone that’s worked with clients, it’s a real barrier. The goal is not to force action, but to instead try to offer the best solutions.

HIIT is quicker, proves to be more effective for fat loss, creates metabolic changes, improves body composition, and helps with muscle retention—but everyone can’t do it. LISS is safer, but takes twice as long to accomplish similar goals and has physiological limitations in terms of metabolic changes.

Better Fat Loss Solutions

If you’re looking for diet and fitness help, learn how you can work one-on-one with a Born Fitness coach to create your own personalized plan. Learn more here. 


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  1. So far i must say this is the best information i have come across for HIIT/LISS.
    There are plenty of videos out insisting on just HIIT but i am now clear that even Low-intensity workouts are beneficial mainly to build your stamina.
    Nice information Adam.

  2. Exactly! But too many high-intensity workouts can lead to burnout, overtraining, or even injuries. The key to a well-rounded cardio program is to include all levels of intensity each week so that your workouts don’t get stale and your body isn’t always doing the same thing all the time.

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