How many calories do you burn during weight training?

This blog is a poignant one for me because I hate seeing people work their arses off in the gym to then be greeted by minimal results at the end of the month. There’s nothing worse than trying super hard, or feeling like you are, and getting nowhere. It’s disheartening, but it happens, and I think that in part this is because our expectations of what happens when you exercise don’t quite match up with reality.

Don’t get me wrong, a lack of results can be for many, many reasons…

• You might not be training as hard as you think
• You might be eating more than you think (or not paying attention to your diet at all)
• You might not be sleeping well, which affects a lot in the pursuit of a better body and improved health
• Or it might be a combination of all of the above.

Let’s assume for now, however, that you are putting in the effort in the gym and you’re eating what you think should be a calorie deficit, but you aren’t losing fat. This is where we can talk about the training you are doing.

Recently I posted a poll on Facebook. Over 1600 people entered and the results were interesting. Have a look: 

On top of this a lot of people in the comments section of the post rightly pointed out that it depends. What about weight, height, intensity, volume, rest, sets, duration, etc etc etc…  

And of course this is completely correct, although I did ask in the post what people thought they personally burned in a session, not what they thought people burned in a session in general, but that’s not really important here…

Anyway.

The poll I did was spurred from a conversation I’ve had a few times with clients and people at seminars; in my experience people radically overestimate the amount of energy burned during a resistance training session and at least some of this is because of the popularity of activity trackers. These have become very popular of late, with it being completely normal to look at your steps, your calorie burn during training and your quality of sleep, all on a little wrist gadget. The problem is that some of this information is more reliable than the rest. 

The thing with heart rate-based calorie data is that it makes a few assumptions, namely that your heart rate being elevated correlates to additional movement and so additional energy burn, and this totally works (with a margin of error) when you’re doing continual training such as most forms of cardio.

Cardio is consistent; when you run, row, swim, or bike you are plodding along and your heart rate is relatively steady, thus it is easy to predict a calorie burn for a set time of that exercise. 

But weight training is stop start. Unless you’re supersetting everything and using low weight for high reps (which isn’t really weight training but more like circuit-based cardio) you probably spend as much, if not more time resting than you do actually moving. Despite this, your heart rate will be elevated for most of the time you’re in the gym! This means that your heart rate monitor will assume you’re moving more than you are, and dramatically overestimate your kcal burn. 

Unfortunately, you just can’t do a set, look at your watch and expect the calorie burn based on that heart rate to be correct.

During a typical one-hour workout you might only be moving weights around for up to 10-15 minutes. The rest of the time you are resting and waiting for the next set (and for many, scrolling Instagram). Some watches and trackers are getting a lot better at recording this, but the vast majority (including the popular ones) are still pretty inaccurate, and realistically quantifying resistance training calorie load requires technology to which most people just don’t have access yet.

The number of calories you burn in a resistance training session depends mostly on three factors – how much volume you’re doing, what movements you’re doing, and how big you are. A recent study (1) found that: 

• Training volume (sets multiplied by reps multiplied by weight) was one of the largest factors in predicting energy expenditure during a training session
• The muscle group matters – you burn more calories squatting than doing curls
• Muscle mass predicts burn, with men burning roughly 161kcal in the experimental session and women burning roughly 87, but the difference being explained entirely by muscle mass. For those interested, the ‘afterburn’ was also less than 10 calories, so don’t think you’re burning oodles of calories while you’re sat down after your weights workout

In fact, to predict your energy expenditure from a resistance training session they came up with this nifty equation (which, when broken down, isn’t as complicated as it looks). It’s not perfect as it doesn’t account for different exercises and that certainly matters (it equates squats and machine lateral raises, for example), but it’s the closest science has come to being able to answer the question we raised at the start of this blog and it’s probably pretty accurate if you only include compound movements:

Total net kcal = 0.874 (height, cm) - 0.596 (age, yrs) - 1.016 (fat mass, kg) + 1.638 (lean mass, kg) + 2.461 (total volume [sets x reps x wt] kg x 0.001) - 110.742

We’ll go through it now. Skip this bit if you’re not interested in the complex maths and just want to get to the point! 

To go step by step, you’ll need your height in cm, your bodyweight and your bodyfat percentage (this can be a guess for now), your age and your total training volume for a given session. To work this last bit out, multiply the number of sets by the number of reps you do, then multiply that by the weight lifted for that exercise. Add all the exercises together that you do and write it down.  

Step 1: Multiply your height in cm by 0.874. Write this down and label it as A

Step 2: Multiply your age in years by 0.596 and label it B

Step 3: Multiply your weight in kg by your bodyfat percentage expressed in decimal format (so for an 80kg person at 18% bodyfat, do 80 x 0.18). Now multiply this by 1.016 and label this C

Step 4: Multiply your weight in kg by your fat free mass expressed in decimal format (so for our 80kg example, their fat mass is 18% so their fat free mass is 82%, or 0.82. They would do 80 x 0.82). Once you have this multiply it by 1.638 and label it D

Step 5: Take the total volume that you worked out a moment ago and multiply by 2.451, then multiply that by 0.001. Label this E

Step 6: Put it all together. Calculate A – B – C + D + E, then subtract 110.742. That’s how many calories that session would burn for you over and above what you would ordinarily have burned in that time, roughly.

For some examples, let’s say that three people do a typical full body workout consisting of:

• Squats: 5 sets of 5 reps with 80kg
• Overhead press: 4 sets of 8 reps with 40kg
• Romanian deadlift: 3 sets of 10 reps with 80kg
• Barbell rows: 4 sets of 8 reps with 60kg

That’s a total of 7600kg of volume. 

• A 155cm 30 year old with 45kg of lean mass and 17kg of fat mass would burn 193kcal
• A 165cm 45 year old with 50kg of lean mass and 20kg of fat mass would burn 198kcal
• A 176cm 20 year old with 65kg of lean mass and 15kg of fat mass would burn 252kcal
• A 168cm 40 year old with 55kg of lean mass and 30kg of fat mass would burn 201kcal

These numbers aren’t very high for a session that would take 60 minutes (if the weights used were challenging) and your number probably isn’t all that high, either; but therein lies the point. Why is it that you are in the gym in the first place? If your goal is to burn calories, then your aim shouldn’t be resistance training, it should be cardio. Cardio is, minute for minute, enormously more effective than resistance training at burning calories.

So why do we recommend resistance training for fat loss? Because regardless of the modality, exercise is a TERRIBLE tool for fat loss. Cardio training, which burns the most calories by a long way, is at best associated with modest fat loss when you do a LOT of it, and the weight regain rate is really high (2). Why? Because if you do enough exercise to burn a meaningful amount of energy it makes you hungry, and so you’re likely to eat more (3). You also become fatigued, and so you move around less during the rest of the day, thus burning fewer calories overall (6). Finally, of course, unless you actually enjoy it you’re not going to be doing ‘a LOT’ of cardio for the rest of your life so as soon as you get bored, you’ll stop and your energy balance will adjust accordingly. 

As such, the idea of exercising for fat loss is one that gets too much weight. The data suggest that moderate exercise participation is an important tool in maintaining weight loss once it’s happened (2) (more on why that is another day) and of course the health promoting benefits of exercise can scarcely be overstated so we hope this doesn’t sound like us saying to not bother with it - exercise is important – but not every tool is right for every job. Exercise for muscle mass, bone density, strength, join stability, balance and mobility, use other things for fat loss.

Now with that being said it’s not true that increasing your calorie expenditure when trying to lose fat is a bad idea; you’re just better off doing it in a way that doesn’t make you tired or hungry, and that means that instead of increasing exercise, look to increase NEAT or Non Exercise Activity Thermogenesis: calories burned through non-exercise movement during the day. 

You can increase activity by walking more, fidgeting more, taking walking meetings, taking the stairs, playing, dancing, lifting bits around the house, gardening, just MOVING more. This could significantly improve your success losing body fat because it increases your energy burn without increasing appetite or fatigue. Just as importantly, daily activity may improve your mood and overall wellbeing in general, with inactivity seeming to be a massive factor in the development of both mental (4) as well as physical (5) ill health.

Too many people are too sedentary thanks to the modern lifestyle, so getting up, moving, walking, taking the stairs, and all of the other little things you can do to minimise sitting time are useful. It really is a win win, there just is no downside. 

Indeed, the importance of NEAT is one reason why exercise is such a poor tool for fat loss. Many people train hard - so hard that later on or the next day they feel knackered, fatigued and sore. This could stop you from moving around as much. Ever done a heavy leg day and the day after you avoid the stairs, don’t want to walk much, and generally slouch about? 

While you may have had an awesome leg session and feel good about that, your next day might see you burn significantly fewer calories because you are in sloth mode. Instead of being vibrant and walking about and generally being active, you are the king of sitting and taking the elevator.

Indeed, while there seems to be variation between individuals the evidence suggests that participating in anything over moderate exercise reduces NEAT (6).

There is SO much inspiration and so many ideas online; people doing amazing things, people lifting mad weights and seeming super strong, people flogging themselves daily on their WOD - this is all well and good, but ensure you are shaping your training for your goals and you know the effect of that training, not just in isolation, but as a part of a wider lifestyle. Exercise is a poor tool in weight loss, and it doesn’t burn as many calories as people think, and the answer to that is not to exercise more.

It's to realise that exercise is a tool for improving your health, building muscle, making you feel awesome and boosting your mood.

Then find and utilise other tools, namely nutrition and NEAT to manage your daily calorie balance. This will see you lose and maintain weight far more sustainably, after all, what happens if you can’t get to the gym for a week, does your fat loss stall?

In short: 

• Exercise for health, strength, and fitness
• Eat for bodyfat control
• Use NEAT when you need a boost

Squatting for the calorie burn misses the point…

Want more science on nutrition and training? Ensure you’ve nabbed a seat on our free short course, which you can get below. 5 days to a more knowledgeable you… 

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References

1. Lytle, J., Kravits, D., Martin, S., Green, J., Crouse, S. and Lambert, B. (2019). Predicting Energy Expenditure of an Acute Resistance Exercise. Medicine & Science in Sports & Exercise, p.1.
2. Swift, D., Johannsen, N., Lavie, C., Earnest, C. and Church, T. (2014). The Role of Exercise and Physical Activity in Weight Loss and Maintenance. Progress in Cardiovascular Diseases, 56(4), pp.441-447.
3. Martin, C., Johnson, W., Myers, C., Apolzan, J., Earnest, C., Thomas, D., Rood, J., Johannsen, N., Tudor-Locke, C., Harris, M., Hsia, D. and Church, T. (2019). Effect of different doses of supervised exercise on food intake, metabolism, and non-exercise physical activity: The E-MECHANIC randomized controlled trial. The American Journal of Clinical Nutrition.
4. Elfrey, M. and Ziegelstein, R. (2009). The “inactivity trap”. General Hospital Psychiatry, 31(4), pp.303-305.
5. Villablanca, P., Alegria, J., Mookadam, F., Holmes, D., Wright, R. and Levine, J. (2015). Nonexercise Activity Thermogenesis in Obesity Management. Mayo Clinic Proceedings, 90(4), pp.509-519.
6. MELANSON, E., KEADLE, S., DONNELLY, J., BRAUN, B. and KING, N. (2013). Resistance to Exercise-Induced Weight Loss. Medicine & Science in Sports & Exercise, 45(8), pp.1600-1609.