Weights vs. Cardio: Which should I be doing if my aim is to ‘recompose’?

The most common question I get when talking about exercises for recomposition is whether weights or cardio will be better for the client’s goals. The answer to this is going to depend very much on each client’s needs and goals, but there are a couple of universals. Some weight training as part of any general recomposition plan is a non-negotiable part of the plan. Cardio is a bit more particular, and I would only recommend it in certain circumstances. Lets take a look at the two forms of training, what they do and how they should be used.

What do we mean by body recomposition?

Recomposition is a process of changing your body’s composition – what it is made of. 80kg at 25% body fat for a man, is a very different picture to the same 80kg at 12%. Generally speaking, composition goals tend to be about getting more muscle and less fat into the same or similar weight footprint.

A comprehensive fitness program should consist of a combination of different types of training to maximize results, and build an overall level of ability in each area. This usually incorporates a combination of strength and conditioning, metabolic training, stretching, and functional training. This is to build an overall fitness program and optimize the body for all aspects of life. Of these though, functional training and stretching are more enablers in a recomposition programme, while the strength and conditioning and the metabolic training do all the heavy lifting (pun intended) with the actual recomposition.

When to use weights in recomposition

Weight training is often not the first thing most people think of when they think of exercising for a fat loss programme. Think of the countless images in ads and movies of people running or skipping or rowing. Weight training is more commonly associated with a goal to build strength and muscle mass. However, when considering the value of weights vs cardio for a recomposition programme, lifting weights has an essential function: to preserve the muscle mass we already have.

We will talk diet in more detail below, but in general terms, a recomposition diet will involve a calorie deficit of some form. That means eating fewer calories than your body is expending. In this context, we must limit out expectations of how much new muscle the body is going to be able to build. With the exception of people completely new to weight training, most people will not be able to gain a lot of mass while in a deficit.

So why do it? Well, muscle is incredibly expensive for the body to maintain. In other words it takes a relatively large number of calories to maintain your muscle mass when compared to maintaining fat or bone. The outcome of this, is that when your body is in a caloric deficit, the body will need to make cuts, and as a metabolically expensive tissue, the body will, if left to its own devices cut muscle first. It will do this unless there is some reason not to. The body is smart, in that it will not cut tissues which are actively being used. If you are sending signals to the body (by lifting weights) telling the body that you are using the muscles, the body will preserve those muscles which are being used. If you don’t send those signals, then the body will reduce tissue size in all tissues, but it will start with those tissues which will spare it the most calories, and that’s your muscles.

But I didn’t want all that muscle anyway!

Actually, you really do. Unless you are a professional sportsperson in some very specific sports, more muscle is almost always a good thing. We will all undergo some muscle loss eventually in our lives. The process accelerates in our 40s and 50s, and so I always advise clients to pack on as much muscle as they can before these ages, and then just work to preserve it after this time. With a good level of muscle mass, preserved through regular weight training, we can have full, productive, and quality lives into our 70s and beyond. Planned for well, we may never reach a time when we can’t get out of a chair by ourselves. But coming back to recomposition, more muscle mass, means a higher metabolic rate, which means we can eat more, while still losing weight. If you lose a lot of muscle, it will affect your metabolic rate, and you will have to eat an ever decreasing number of calories to maintain losing weight (to a point).

The upshot of all of this, is that weight training is an absolute essential parto f any recomposition programme, and separate to that, I would say is an absolute essential part of anyone’s fitness routine.

When to use cardio in body recomposition

Cardio is a type of training that involves working at a moderate-to-high intensity for a period of time. It is a form of training that can be used to help increase the body’s ability to use oxygen while improving overall health and fitness. A well trained cardiovascular system will mean you are able to climb stairs, run for the bus, or just generally go about your day without getting out of breath. Cardiovascular health is an absolute must for everyone. A healthy cardiovascular system is a huge mitigating factor in a host of health risks. To train the cardiovascular system well you need to do a couple of different types of training: long slow distance type at a low level heart rate (zone 2) will improve your aerobic base, while HIIT training will improve your anaerobic threshold. These types of training do take time, and are worth doing for their own sake. When it comes to recomposition however, the story is not as clear as all that.

We used to think that if you spent 1 hour on a given day running, and burned 800kcal in that run, that this would automatically put you into an 800kcal deficit, and that the body would take the excess from your fat stores. Cardio was therefore all about creating a deficit through greater activity. Unfortunately the most recent science on the matter indicates that this is not what happens. Instead, the body seems to want to stick within its own limited number of calories that it likes to consume, and, instead of burning new calories, will make cuts to other parts of expenditure in order to accommodate the extra calories required for the exercise. An 800kcal run, which is not replenished with food, may for example cause the body to cut the budget of the immune system by 300kcal, brain function 200kcal, and dopamine production of 100kcal, new calories burned then would be only 200kcal, and the rest would be calories redirected from other systems.

So when it comes to burning through calories, cardio is not anywhere near as efficient as we used to think. The body is too smart a manager of resources to always dip into storage when energy is low. So the real question of the article is really not a toss-up between cardio and weights, but actually a toss-up between creating a calroie deficit through cardio, or creating it through food.

I have limited time – what should I focus on?

It seems pretty clear from above, that as far as time-efficient ways to engage in a recomposition programme goes, weights is a non-negotiable, while cardio seems optional. The creation of a calorie deficit through cardio is incredibly inefficient, and most especially is time-inefficient. If we choose to instead take a calorie controlled way of eating, and create out calorie deficit through that, then cardio ‘exercise’ becomes an optional, and for some people I would not even suggest that they do any dedicated cardio ‘exercise’. I’m using ‘exercise’ here to indicate cardiovascular work which is just going through the motions in order to burn more calories. This is separate from cardiovascular ‘training’ which is specific and targeted work to train and get the cardiovascular system stronger.


If you thought I would end this article with an on-the-fence result saying that “Weight training and cardio are both important parts of any recomposition program” you’re about to be disappointed. In my mind weight training to preserve muscle whilst eating to a calorie deficit is the best and most sure-fire way to achieve success in a recomposition programme. If you want to simultaneously throw in a HIIT session to keep your heart in tip-top shape, then that’s great, and I’d recommend it, but don’t do it thinking you’re burning through new calories. One final thing I haven’t mentioned is NEAT – Non-Exercise Activity Thermogenesis. This is the general level of activity you have during the day outside of your workouts. It is getting up and moving around between zoom calls, walking to the shops or the station and so on. This type of activity is really important to keep high for general health and will be a great plus to your recomposition programme. As ever if you’d like to discuss this and more, and get specific in how to recomp yourself, get in touch and book a DEXA.

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