October 20

Calories and energy balance: It’s simple, right?

Calories in, Calories out. How many times have you seen this on your social media recently as the holy grail of nutrition? The only thing you need to consider. Generally, this is talking fat loss, and although the message is wholly accurate, it can also be pretty misleading- even harmful if not fully understood. So, here’s something for athlete’s, coaches and gym goers to try to cover some of the key considerations when we’re talking energy balance.


First off, what is energy balance?

Energy balance is a simple concept. If energy in (Calories we consume) exactly meets energy out (Calories we burn), we are in a state of energy balance, and weight will remain stable. This is the thing plastered all over your news feed, about how there’s nothing more to consider. The thing is, as soon as we get past this initial concept, we run into problems.

Now, before you throw your phone/ laptop away in disgust, I’m not saying the concept is wrong. It’s absolutely not. I’m just saying it VERY misunderstood.

Here’s just a few of many issues we face:


#1 Weight change, fat loss and Calories

The idea is, you consume less than you burn, you’ll lose weight. You consume more than you burn, you’ll gain weight. SIMPLES. Well, not quite.

What do we mean by weight loss? I’d argue that more often than not here, we’re talking about fat loss. If not, we’d need to consider hydration status, etc, and that absolutely doesn’t stand true when it comes to energy balance. So, we’re talking fat loss. Naturally then, we should probably consider the potential to drop bodyfat WITHOUT a decrease in weight….

Hang on a minute! How would this happen? We’d need to be in an energy deficit to drop weight?! Yep.

But we can’t build muscle in an energy deficit? Ahh, now that’s not quite true.

We probably won’t maximise muscle building, but we certainly can increase lean tissue in a slight deficit overall, particularly if you’re not already advanced with this. But here’s a key point: Certain nutrient intakes make this much more likely than others. Protein can contribute to exercise energy metabolism, but generally far less than fats or carbohydrate. Remember, building muscle/ lean tissue will require adequate protein intake (and exercise stimulus), and ENOUGH ENERGY to cope overall. So, where does that energy come from?

Just the food we consume at the time, mainly carbs or fats?

Now, from an evolutionary perspective, that would make storing HUGE amounts of body fat pretty redundant, right? See where I’m going with this?

We store energy in our body- primarily as glycogen (carbs in the muscle and liver), and as fat, in the muscle and adipose tissue. Why? For future use….


#2 Stored Energy

Our nutrition, exercise, and training status can all influence where we get this stored energy from. The issue is that people often inhibit fat loss by either being sedentary and inefficient at utilising stored fats, by consuming carbohydrate in quantities that will inhibit fat burning (but not energy use),  or by consuming low carbs as to avoid this inhibition, but then consuming more total calories than they need, meaning they burn fat- lots of fat- but total fat doesn’t reduce.

And, why’s protein important for this? Protein isn’t a particularly good “energy source”, and is essential in structural processes such as building lean tissue, building enzymes, transport, and all sorts of other goodies. So, consuming plenty of protein allows these processes to run pretty efficiently, even if you’re taking in less energy than you’re using.

So, in a moderate energy deficit on paper, we can actually be building some lean tissue, staying perfectly healthy, and getting less fat. And this relatively long term energy deficit may not result in weight loss.

That’s when it goes well.

But be careful. You could also be in a perfect energy balance, and get a little bit less lean, and a little bit more fat, depending on how you’re using the fuel and nutrients you take in. To be fair, intuitively, you probably had a hunch, I’m just here to explain that this is actually possible. Calories in, Calories out. Here’s how that equation really looks if we go a layer deeper:

Energy Intake + mobilised energy stores:

Calories consumed, absorbed and assimilated + stored energy available and mobilised.


Energy Output:

Resting metabolic rate (RMR), Thermic effect of foods (TEF), Physical Activity (exercise energy expenditure and non-exercise activity thermogenesis) (PA)


Sure this stored energy will come from somewhere, but the nutrients we consume, the times and amounts we consume them in, may all have a big impact. Fats can be converted to glycogen (although not easily), but the more important point is with high carbohydrate available, this is our preferred energy source: meaning more fats are stored. For this to not matter, we’d need to assume the role of fat and carbohydrate is the same when it comes to energy metabolism, and that there are no differences in hunger, appetitie or function between the nutrients, and that’s simply not the case.

So, energy balance matters, but so does nutrient availability. Completely true, but not completely simple.


#3 It’s an educated guess anyway, so don’t worry so much!

So, now that we’ve got the complex bit out of the way, here’s just another consideration. See the equation above?

EI= Calories consumed (+ stored energy available (let’s ignore this bit for now, I’ve made my point))


So, the goal is, to balance the equation for adequate energy intake and weight maintenance (or obviously bias it one way for a change in weight). Here’s where tracking everything to the gram isn’t perfect regardless of how much you try.

So, energy intake….

We can track food, but this has a whole host of errors. From the tracking software we use, to this bits we forget to track, to the changes in the actual calorie composition of different foods, this will be approximate, but not perfect. And that is the best out of the lot!

The next step relies on good, healthy digestion, which plenty of people lack. I wonder how many calories are lost along the way? In addition, we use energy to break food down, transport it, store it, and more. And this leads us nicely on to Energy Out….

So, the above is both a part of the thermic effect of food, and possibly the resting metabolic rate, depending on which part of the process we’re looking at. But clearly here, calculating exact amounts of energy used will be difficult outside of the lab. Again though, we can have a good guess, and just account for some possible errors. We will still be in the ballpark, and there’s some great ways to help you to stay consistent with this (activity trackers, etc).


#4 Activity Calories (Here’s the best bit..)

Physical activity. Now this is more difficult to track the energy expenditure for. In a lab, we can get a really good estimate through direct or indirect calorimetry, and even have a good idea on what fuel we’re using (carbs or fats), but in the real world, this just isn’t going to happen. So, that workout calories estimate may be way off.

And beyond that, we actually don’t care that much about the workout calories. It’s only a part of the equation! We care about the total balance of the equation (and some!), and our body has some cheeky little tricks to get around this.

First off, compensatory mechanisms mean that if we’re low on energy, we may find that we move a little bit less for the rest of the day, subconsciously trying to conserve energy to keep within that energy balance. Or if not, substitution effects sometimes do the work for you, meaning you swap one form of activity (Eg. housework and walking the dog) for another (a gym session). And beyond this, we’ll usually up regulate appetite initially, so we may train harder than usual, burn more calories, and then eat more to make up for it.

Sometimes, the net benefit is officially zilch, zero, nothing. Ever found you didn’t lose weight on that new exercise plan? Well, this is probably why.

I’ve not even mentioned tracking progress here, but I covered that in a recent post. Check it out here!

Our body is smart. It’s trying to keep you alive. Don’t hate it, just be smart and hire a coach.

So, all things considered, you need to be ok with using educated guesses, and looking at the big picture when it comes to fat loss.


So, what can we do to succeed?

It’s actually pretty simple. We can have a good guess with all of this. Estimate a rough energy output, and get pretty close with tracking energy consumed. We can keep track of our digestion (and lifestyle), and deal with issues as they come up. But the main thing, is probably to stop being obsessed with calories.

They matter. Absolutely. Still track your nutrition, be consistent with your activity, and make sure it works for you.

But particularly during your workout, think about what you’re trying to achieve. That calories used tool on your HR monitor isn’t as important as you think when it comes to fat loss. New to exercise, and wanting to burn fat and build baseline fitness? Low/ moderate intensity, with an appropriate fuelling strategy (probably limiting carbohydrate) is probably a great approach. Advanced looking to maximise performance? You probably want to include enough carbs to fuel the high intensity performance, and ensure you fuel yourself appropriatey for the secondary adaptations, and the calorie burn can help you to understand how to fuel for this, providing you’re aware of inaccuracies.

Consider the big picture.  I know, you won’t be able to just guess with this. You’ll need a coach.

But it will work. If you want to get started, book a call, or email josh@fxfitness.uk

So, Calories in, Calories out. Simples.


Josh Kennedy MSc, ASCC, CSCS


P.S. Here’s my social links! I try to get simple, useful content out on here! Facebook & Instagram.


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