Why more cardio is not better for weight loss

You can sweat it all out - to a point. (Image) iStock

If you're trying to lose weight or build fitness, it can be tempting to think you need to run all day every day. But experts say that cardio is not the be-all and end-all – and too much could actually sabotage your exercise efforts.


"Sometimes less is more – it's a case of training smarter, not necessarily harder," Greg Stark, trainer at Better Being, told Coach.

"When you do more, you start to increase your risk of injury which could set you back even more. You can also start to put yourself under chronic stress because your body is not getting that opportunity to recover and that causes inflammation in the body, which slows down your body's ability to process fat."

If weight loss is your goal, Stark says you generally want to do cardio and a couple of weights sessions a week.

"The biggest danger is that by doing a lot of cardio and no resistance training, you are going to sacrifice some muscle tissue " he explains.

"If we're trying to lose weight, at a minimum we want to maintain what muscle tissue we have while burning body fat."

That's because a greater muscle mass will burn more fat when your body is at rest.

"Having more muscle is like a car with a bigger engine – you will burn through more during the day when you are at rest," Stark says.

"Getting your heart rate elevated by doing the cardio-based stuff is going to help with your overall expenditure and create a slight calorie deficit, and your resistance training and protein intake is going to help maintain your muscle mass."

So that's not to say cardio is pointless – it's definitely one of the best things you can do for your body.

"Cardio is great for energy expenditure and benefits your cardiovascular fitness," Stark says.

"It also has brain benefits and will probably enable you to make better, healthier decisions. That's because your brain releases a hormone called BDNF – brain-derived neurotrophic factor – which is basically fertiliser for your brain that brings better clarity of thought, mood and focus."

Diet will always make the biggest difference

Stark is at pains to point out that you can't "out-run" a bad diet, and that if weight loss is your goal, then you need to make sure you're eating slightly less than you're burning.

"With weight loss, first and foremost you have to create a calorie differential between what you are expending through exercise and what you are consuming," he explains.

"Saying that, you don't want huge calorie deficits because that can have a negative impact on your ability to lose weight – cutting back by 500 calories is what the recommendation is."

So even if you're working out like a Trojan and are ravenous, unfortunately you can't eat heaps more and still expect to drop centimetres.

"If you're eating more than what you are expending you are not going to get that weight loss," Stark says.

How much cardio is best?

The Australian Physical Activity Guidelines suggest doing up to five hours of moderate intensity exercise or up to 2.5 hours of vigorous exercise each week, plus do muscle strengthening exercise at least twice a week.

Stark says that's generally a good rule of thumb.

"To get a significant benefit out of resistance training you need to do it at least twice a week and you want to try to do something active twice a week as well," he says.

"Sometimes your body will feel fresh so doing something intensive and harder is a good recommendation, but if you're feeling sore and a bit rundown, go out for a nice gentle walk and still expend those calories but not necessarily put your body under too much stress."