Does Cardio Really Work for Weight Loss?

When I first started on my weight loss journey I was just as lost as everyone else as to what I really had to do to achieve my goals. Some friends touted just dieting, others were proponents of a lot of running. I was referred to Bill Philips’ Body-for-Life program by a friend as a starting point. Bill takes a holistic view on changing your lifestyle to achieve your fitness goals. It then became clear to me that while cardio was an important aspect of losing weight (fat), it was only one of 3 things one had to do to get there. An overall bodyweight loss of about 14 KGs in 12 weeks is testament to the fact that the trio really works. You’re probably thinking, what are the other two things? Read on.

How does one lose weight?

First let’s get into the simple mechanics of weight loss. Weight loss occurs when the body is put through an energy deficit which is measured in calories. When you consume less calories than what your body requires to maintain a steady state (homeostasis) you end up losing weight. That’s the simple science behind it. Consume less calories than required and you’ll lose weight. Of course the energy requirement will vary based on your age, gender, lifestyle and current bodyweight. I’ll cover the specifics of how this can be achieved in the next section and what sort of results you can expect.

How does one reach calorie deficit?

There are only 2 ways to ensure you have less calories in the body.

Eating less is fairly straightforward and you basically cut back on the amount of food consumed through the day. While this will result in weight loss you’ll end up losing both muscle and fat. Fat loss is good but muscle loss isn’t because this kind of calorie deficit isn’t sustainable. Although you’ll lose weight doing so, cutting back too many calories can be detrimental to your health.

Exercising is where different viewpoints come into play. You have the choice of doing cardio alone or just weight training or a mix of both (concurrent training). While each exercise style will be beneficial for creating a calorie deficit a combination of both cardio and resistance training is sure to boost fat loss and at the same time increase muscle mass. Increase in muscle mass leads to better metabolism and you could be burning calories away even while you rest. Cardio on the other hand only burns calories when the activity is being performed, unless of course you engage in high intensity interval training or HIIT. Marc Perry from Built Lean has an in-depth post on whether cardio or weight training is better for weight loss.

What does cardio do to the body?

Cardio exercises get your heart rate up and get oxygen pumping through your blood. They’re great for your lungs and heart and help ligaments and tendons in preparation for higher intensity exercises. Overall a great way to get in shape if you just like being active. Cardio done the right way will result in fat loss.

So what is the right way to do cardio exercises? It comes down to your goals. If you’re only trying to improve endurance low intensity steady state (LISS) cardio will work but only if you can spare between 30–90 minutes. Low intensity cardio uses the body’s fat stores as an energy source. If you want to build muscle then anything over 45 minutes is going to be detrimental to progress due to catabolic reaction which causes muscle tissue breakdown. This is a great way to get started if you’re new to exercising. Just take the pushbike out or go for a run. Too easy!

This is where HIIT comes in. HIIT is a short and intense workout which winds your body’s metabolism up like a clock and keeps it ticking well after the workout is complete. The high intensity ensures that you burn just as much if not more calories as a 45 minute low intensity session. High intensity here means pushing your heart rate up to about 90–95% of your max heart rate for intervals as short as 15–30 seconds. This can be very demanding on the body and should only be undertaken once you’ve reached a certain degree of fitness.

You can follow the LISS vs HIIT cardio debate at Gymaholic.

Why is cardio alone not as effective?

This comes down to something known as the basal metabolic rate or BMR. OMG! More jargon. Let’s break this down: BMR is the amount of energy expended when the body is resting. Low intensity cardio only burns calories when performing the exercise and does little to help the metabolism rate once completed. The fat is only expended as an energy source AFTER the workout is completed. Its unlikely that you’ll spend 5 hours a day doing light intensity cardio only to burn of calories. It’s just plain boring. HIIT on the other hand is known to boost your BMR for up to 24 hours after performing the exercise which means you end up burning more calories even after the workout is completed. This is known as the afterburn effect.

All of this works for as long as you continue with your cardio exercise routine. But what happens when you stop? You end up in a calorie surplus because you haven’t built up muscle mass to sustain a higher BMR. Remember high BMR = high calorie burn while resting. Packing on more muscle increases the BMR. The body likes to stay in a state of steadiness and thus in order to preserve muscle mass the body expends more energy. Muscle mass is built through resistance training.

What really works?

Steve from Nerd Fitness puts it across really well:

If you are interested in getting in shape, the MOST important thing you can do for yourself is adjusting your diet.

Cardio on top of a diet is found to produce marginally better results compared to dieting alone. Concurrent training i.e. a mix of both cardio and weight training along with diet control has been found to deliver 40% more fat loss than the previous two methods.

Adjust exercise to suit your goals

Cardio definitely has a place in your fitness routine. If you’re only starting out and have a grip on your diet and just want to feel active go for cardio alone but don’t overdo it i.e. keep it under 45 minutes per session. If you want to step up your fat loss and body transformation to the next level it’s important to incorporate resistance training with cardio and diet. If your preference is just to stay active cardio alone can be great way to keep your body ticking. Be advised though that it will take longer to reach your fat loss goals with cardio alone.

Professor Boutcher from University of New South Wales has this to say about exercising:

Overall, any type of exercise is good. You just have to work out your objectives, whether it is to increase muscle, lose fat, or enhance other aspects of your life such as improving the quality of your sleep

Originally published at on May 26, 2015.

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