Is Cardio Really the Secret to Fat Loss?

One of the most talked about subjects in the fitness industry is cardio and fat loss. Here's what our clients (and yes, even us trainers) want to know: Is cardio necessary to lose fat or, similarly, to achieve a weight loss goal? The good news is that there is some pretty clear research that can answer this question. 

First, it’s important to understand how cardio is different from weight training. Then we’ll discuss the role this type of training plays in fat reduction. We end with a comparison of cardio workout options for reducing body fat, also providing additional actions to effectively lose weight.

Aerobic Exercise vs. Anaerobic Exercise

There are two basic types of physical activity: aerobic and anaerobic. To understand how our bodies lose fat during training, and to be better able to explain it to clients, it’s helpful to know what these terms mean.

• Aerobic activity. Aerobic training requires the presence of oxygen. This type of activity primarily works type I muscle fibers. This helps increase muscle endurance and capillary size. It also generally helps the heart muscle pump blood more efficiently. 

Aerobic activity is done at a pace you can sustain for an extended period. Think 50% to 70% of VO2 max and a heart rate between 120 and 150 BPM. Lower-intensity jogging, swimming, or biking are examples.

• Anaerobic activity. This is the opposite of aerobic activity. Anaerobic training involves exercise that does not require the presence of oxygen. It works the type II muscle fibers, which leads to greater muscle size and strength. Sprinting until you gas out or weight lifting with heavy weights is anaerobic. 

When you work at 90% or more of your VO2 max during anaerobic activity, oxygen builds up. Lactic acid also builds up and you start to feel the burn. You can't sustain anaerobic exercise for extended periods like you can aerobic exercise.

Knowing how the body reacts to each type of exercise makes it easier to recognize their different effects. It also makes it easier to answer the burning question: If your goal is to change your body composition and lose excess fat, is cardio necessary?

Is Cardio Necessary for Fat Loss?

The quick answer is no. You do not need to do cardio exercise to lose fat. That said, it’s not completely useless. Research has shown that doing cardio can aid in weight loss.

One piece of research analyzed reviews of 149 different studies. Each involved subjects who were overweight or obese. Those engaging in cardiovascular exercise achieved both fat and weight loss. 

Just because cardio isn't necessary for fat loss doesn't mean you shouldn't do it. Other cardio benefits make it beneficial to perform. For example, in the research mentioned above, subjects doing cardio also lost a good deal of visceral fat. Visceral fat is also known as belly fat since it sits around the midsection. Reducing this fat helps improve cardiometabolic health.

The Cleveland Clinic shares additional benefits of regular cardiovascular exercise, including:

• Protecting the brain from age-related cognitive decline

• Contributing to better joint health

• Improving skin health, reducing effects of stress or normal aging

• Aiding in muscle health

• Assisting with digestion

• Increasing energy

• Improving sleep quality

• Bolstering immunity

• Decreases risk of sexual dysfunction

In short, cardiovascular exercise contributes to optimal health while assisting with fat and weight loss. And certain types of cardio are better for the latter.

HIIT: The Best Cardio for Fat Mass Reduction

There are several ways to engage in cardio exercise. One option is to do low-intensity steady-state cardio. An example would be walking on the treadmill at a lower speed or incline for the duration of the workout. Another option is high intensity interval training or HIIT. During a HIIT workout, exercise intensity varies from easy to hard in timed intervals. 

Which type of cardio will optimize fat loss? Should you do low-intensity steady-state cardio or focus primarily on high intensity cardio interval workouts?

The traditional outlook on cardio and fat loss was that a good, long, low-intensity workout on an empty stomach would lead to the greatest fat loss. A long, slow run first thing in the morning is the go-to daily workout for a lot of people. Views on this are changing, though, with research to back it up. 

Research tells us that HIIT is a powerful way to lose fat when compared to steady-state training. Lower-intensity aerobic cardio can lead to fat loss, though in lower amounts. It may even hinder muscle growth when compared to HIIT workouts.

For example, one study reports that fat oxidation, the use of fat molecules for energy, is significantly higher after high intensity interval training. In other words, HIIT causes the body to target fat stores for energy. This means greater fat loss.

One explanation for the greater fat loss experienced with HIIT is that this type of exercise may increase excess post-exercise oxygen consumption (EPOC). After a HIIT session, you continue to oxidize fat more than after a low-intensity steady-state workout.

Researchers have also found that HIIT workouts can increase the levels of growth hormone in the body. This may further contribute to fat loss.

Other Effective Ways to Burn Fat

Cardiovascular exercise is only one way to lower body fat. You can also lose fat by restricting calorie intake, doing strength training, or with a combination of both.

Create a Calorie Deficit

The main factor in losing body fat is taking in fewer calories than we expend. This creates a caloric deficit. When we consume fewer calories than needed, body fat is used for energy. This is why you can lose weight on low-calorie diets. You aren’t eating enough to meet the body’s energy demands.

The key is to keep one’s calorie deficit reasonable. Cut calorie consumption too much and it can make weight loss harder. Plus, once you go off a very low calorie diet, the consequence is often weight gain.

Start Lifting Weights

Restricting caloric intake is an obvious solution to fat loss. If you consume fewer calories, you will burn and lose more fat. But, what about weight training? How does that help with fat loss?

Strength training is one of the best ways to get lean because you’re building muscle. When you add muscle, you raise your resting energy expenditure (REE). This is the number of calories you burn when you're just sitting still.

Muscle tissue requires more calories to function than fat tissue, even at rest. The more lean muscle you have, the more calories you burn per day. Over time, this contributes to weight loss.

Combining a Calorie Deficit with Strength Training

Combining the two approaches helps attack body fat both ways. Limiting calorie consumption forces the body to use its fat stores for energy. You’re burning calories just to survive, let alone exercise. 

Adding weight training increases lean body mass. The more muscle mass you have, the easier losing weight becomes.

Vary Cardio Training for the Best Results

There is a time and a place for all types of exercise and both types of cardio. Both aerobic and anaerobic training provide a lot of benefits. But if you want to majorly change your body mass, HIIT is the front-runner when it comes to burning fat.

So, if your client's number one goal is to lose weight, focus on HIIT. But don't leave out other types of training. Also remember that if your client is a beginner, HIIT may not be the right method of training right out of the gate. They may need time to work up to a fitness level where they feel comfortable enough to do interval workouts. 

Resistance training builds muscle and leads to higher resting energy expenditure. Steady-state cardio also has benefits. They include increased muscle mass in the heart, better disposal of metabolic waste, more use of fat as a fuel instead of sugar, and increased fat oxidation. This lower-intensity cardio may not burn as much fat as HIIT, but it still does the job while also providing health benefits and a little variety.

Expand Your Strength and Conditioning Expertise

Now that you have the answers to the most pressing questions about cardio workouts and fat loss, you can better plan a fitness schedule for yourself and your clients. Ready to add more to your bank of knowledge and skillset for personal training? Sign up for the ISSA's Strength and Conditioning course!