Cardio or weights – which should you do?

When people decide that they want to improve their health they tend to alter two primary things, namely their nutrition and their exercise habits. Most of the blogs on this site are designed to help you with the former but this will be a quick overview of the way that we’d like you to think about the latter.

First of all, the title of this blog is a completely false dichotomy – the question shouldn’t be “cardio or weights, which should I do?” because it’s perfectly fine to do both. Rather, it would ideally be viewed as “which should I focus my attention on the most”, which is a valuable question because you only have a limited amount of time and energy, and there are definitely pros and cons to take into account with both fitness approaches.

The best way to answer this question is to look at the effects of – or perhaps the purpose of – both kinds of exercise so this is what I’m going to do now, starting with cardio.


Cardiovascular training is extremely beneficial, as you should expect, for the cardiovascular system (Your heart and associated blood vessels). In short, when you do cardio your heart gets far more efficient and this reduces your risk of a number of different health issues down the road – extremely valuable, of course. In the realms of body composition changes, the purpose of cardio is a very simple one: it increases the number of calories you burn during the day. Running a mile burns somewhere in the region of 80-110kcal depending on your weight, for example, and if you’re looking to create a calorie deficit in order to lose fat it makes logical sense that this would be extremely useful!


This isn’t the way to really look at it, though.


Cardio does burn calories, but the problem is that unless you’re extremely fit it doesn’t burn all that many in the grand scheme of things – a 10k run will burn in the region of 500kcal – not to be sniffed at, but it comes with the following consequences:

  • Unless you’re very fit that will take a long time to do
  • It’ll make you really hungry, which can make nutritional restraint far more difficult
  • It’ll make you tired, which means you move less during the day, which means that although you burn a lot of calories while running, you then don’t burn a lot of the calories you otherwise would have during the day. Some research has suggested that after around 300kcal of exercise calories, your body compensates for further burn by reducing activity elsewhere.

In short, from a body composition standpoint, the only way that cardio will help is to burn calories and honestly, it’s not even very good at that. If you want to do cardio because you’d like to do it competitively, because you genuinely enjoy it, or because you want the cardiovascular benefits, then doing SOME is a good idea – but if your aim is to alter or control your body weight, there are better options…

This is where resistance training gets a mention.

Now the first thing I want to say is that it’s an absolute myth that resistance training burns more calories than cardio, or indeed that it burns many calories at all. Sure, it does burn some, but that’s not really what it’s for and this shouldn’t come as a surprise to anyone that’s ever lifted weights in a gym – you spend most of your time resting between sets! Some will say ‘what about the afterburn’ and this is worth mentioning – if you lift weights your metabolic rate is elevated after the workout but the effect of this is MASSIVELY overblown. The increased burn will total somewhere in the region of 15% of the calories burned in the session, which will be about 200kcal or so in total, meaning you burn 30 more kcal over the coming day than you otherwise would have.




But this is where I want to make something extremely, extremely clear:

The purpose of exercise is not to burn calories. If you fall into the trap of exercising to burn calories, it’s then a very short leap towards using it to punish yourself for eating or earning the right to eat in the first place – both of these ideas are flat out wrong and an extremely unhealthy mindset to adopt. If you’d like to create a calorie deficit or keep your intake at a weight-maintaining level, then find a way to use your nutrition to manage this in a sustainable way which you enjoy. Use nutrition to control your weight, exercise for your health.

And when it comes to health, resistance training comes out on top. Resistance training gives all of the cardiovascular health benefits I’ve already mentioned (though not the cardiovascular fitness – if you want to be able to run a long way for whatever reason, I’m afraid you have to practice it) but also a ton more, for instance:


  • Resistance training improves glucose tolerance, meaning that it is incredibly useful for either managing or avoiding diabetes. This happens because resistance exercise increases the amount of glucose that your muscles can absorb, and the ease with which they do it
  • Most famously, it helps to build muscle which improves joint stability, is an independent predictor of increased length and quality of life, and makes daily tasks easier
  • It also helps retain muscle both as you age and during a fat loss phase


Cardio doesn’t do any of that (not to mention the higher injury rate in runners compared to literally every other exercise modality) and so if you’re going to do only cardio or only resistance training, hit the weights – it really is a no brainer.

But won’t it make you lose weight slower? Yes, it will, but here’s the dirty secret:

1lbs of muscle contains way less stored energy than 1lbs of fat, thanks to the amount of fatty acids, protein, and water in both. In short 1lbs of body fat contains roughly 2500kcal while 1lbs of muscle contains about 400. Here’s an example scenario: If you create a 2000 calorie deficit (eat 2000 fewer kcal than you use in a week) then your body needs to take some energy from its own stores to function, and if it takes 1000kcal from muscle and 1000kcal from fat stores you’ll lose 2.5lbs of muscle and about 0.3lbs of fat. You’ll see a 2.8lbs change on the scales – but most of that is muscle!


If you do resistance training you won’t lose any – or will lose a tiny amount – of muscle, and so maybe all of that 2000 comes from fat. All of a sudden instead of 2.8lbs you’ve lost 0.6lbs and so weight loss is slower. But that’s a GOOD THING because you’re maintaining the tissue you don’t want to lose. Scale weight, as I hope you know, isn’t everything.

So should you do cardio or resistance training? Well, honestly, do both. The WHO recommends the following weekly:

  • 150minutes of moderate-intensity cardio OR
  • 75 minutes of intense cardio

And on top of this, two resistance training sessions hitting the full body. You could do more than this if you have lofty goals of course, but for general health this is a great place to start. The resistance training would ideally be free weights but there’s no harm in using machines when you first start out and I’d definitely recommend hiring a coach to help you learn the ropes.


But in short, when it comes to choosing resistance training vs cardio – do both! And if you can’t, you’re going to benefit a ton more from pumping iron than hitting the pavement…

"All in or all out" Rachael is a vibrant, no-bullshit-talking Scottish nutrition geek and coach helping women to lose weight without giving up their confidence OR their favourite foods.

Previous postNext post

Sorry, the comment form is closed at this time.