5 years ago, I was scrolling through internet videos of various body builders I followed, and I came across a LOT of information about ‘stoking the metabolic fire’. Cue, advice to eat 7+ meals per day and the notion that your calories should be higher to lose body fat.

These guys had been doing this for WAY longer than I had, so I thought they had to be right…right? Well, a few weeks of 7 meals per day and I had started to develop a bit of a paunch. Turns out, increasing your calorie intake doesn’t lead to losing body fat after all.

I say this jokingly now, but I genuinely believed these guys back then and I can understand why. They were convincing, famous and in incredible shape. Little did I know how much the power of clever marketing lends to selling ideas, good or bad.

Thankfully, I’m much better educated now. So, to avoid you making the same naïve judgement call young Jack did 5 years ago…I’m going to dive right into this to help you understand WHAT metabolism is, WHY it’s not the problem and WHAT you can do right now to help with losing body fat.

What on earth is your metabolism?

In short, the processes that happen in your body to maintain homeostasis. Your body loves staying still basically. If we simplify this to look at both sides of the energy balance equation, we can see that there are things on both sides that impact how much energy is going in and how much is being used. It’s a bit like a see-saw.


1. Conscious Calorie Intake (the calories you know you are consuming)

2. Unconscious Calorie Intake (the calories you forget about or don’t know you are consuming through lack of understanding e.g. not realising how much oil you are using to cook with)


1. RMR (RESTING METABOLIC RATE- The energy you burn at complete rest i.e. the energy you use just staying alive)

2. NEAT (NON-EXERCISE ACTIVITY THERMOGENESIS- The energy you use doing daily tasks)

3. EE (EXERCISE EXPENDITURE- The energy you use during exercise)

4. TEF (THERMIC EFFECT OF FOOD- The energy you use to digest and use nutrients from food)

Does your metabolism actually ‘slow down’?

It CAN do, yes. BUT, and this is a big BUT, not by very much in the grand scheme of things. We’re likely talking the equivalent of 1-3 apples per day. To flesh this out a little bit, here are a few studies that shed some light.

In NYMO, 2018, 36 obese subjects were put through a very low-calorie diet, followed by a 4-week maintenance. Resting Metabolic Rate (your energy used at complete rest, before we take exercise, fidgeting, thermic effect of food, talking etc into account) reduced at 5% of body weight lost, but didn’t reduce further until 16% of body weight was lost. This adaptation was present in all subjects only after 10% of body weight lost. The number of calories dropped from resting metabolic rate was between 50-170 per day and this reduced after weight was stable. The lesson to take? Well, it’s only one study, but it suggests a few things. Firstly, your metabolism may slow slightly, but only at complete rest and not by enough to significantly impact fat loss. There were individual differences, but even at the very height of adaptation, it was only 170kcal. Lastly, it’s pretty logical this would happen. Your body has less mass when you lose body fat/weight, so you need less calories to support it. Forthergill, 2016, Johannsen 2012, showed a similar outcome in regard to metabolic adaptation in that there was a maximum lowering of RMR by 20%, with most cases between 5-10% once the new bodyweight was reached.

Let’s take an extreme example here too. In the MINNESOTA STARVATION STUDY (Ancel Keys), 36 conscientious objectors were put on a 50% calorie deficit, made to walk 22 miles per week (as well as doing manual jobs, meant to mimic the frontline). They lost up to 25% of bodyweight and dropped down to as low as 4-5% bodyfat. After a 3 month recovery phase where they gained weight back, the total amount of resting energy expenditure they had dropped was 600 calories. However, 400 of those came from metabolically active tissue (fat, muscle, organ tissue) and adaptation in resting energy expenditure (RMR) only accounted for a reduction of 200 calories. The take home here…don’t worry about very low calories being damaging for you. The likelihood is you won’t go nearly as low as this and these guys didn’t enter the mythical ‘starvation mode’ after literally being starved.

Now, instead of taking these as be all & end all fact…it’s worthwhile seeing them as examples of what COULD be happening. Everyone is slightly different and actually if we dive into the results a little closer, there is individual variance. However, they all demonstrate the theme of metabolism not acting in the way we’ve been so often told. It’s not as black and white as on or off, fast or slow. Your metabolism is very adaptive and so you should expect to have to eat less at a lower body fat/weight. But you can also have the comfort of knowing you won’t go into starvation mode if you drop your calories by 20%…even if all the magazines tell you that’s what happens. (hint: now magazine probably isn’t the most well informed source for your nutrition education)

So why do people talk about metabolism being the thing that is stopping fat loss?

What I really think it comes down to is facts being taken out of context. Your resting metabolic rate may well slow down a little when you lose weight/fat. What it doesn’t mean is that your body is going into starvation mode, crashing or eating itself. What it does mean is that the energy you use at complete rest drops by up to 20% max (even if your resting metabolic rate is really high this is still only about 3 apples worth of calories per day!). This is because:

1. You lose metabolically active tissue– fat, organ tissue, maybe a little muscle

2. Your muscle contractions become more efficient- essentially your body preserves energy for when it really needs it, so daily tasks use less energy

3. You may well subconsciously make up for trying to eat less by eating more without realising (forgotten foods, portions slowly increasing etc) and moving less without realising (less fidgeting, less moving around at work and at home etc)

4. You are eating less, so you use less energy from digestion.

It’s easy to seek one simple answer that lies at the heart of something more complex, because we’re human after all! But really, metabolism is more than just SLOW or FAST. You also can’t switch it on or fire it up…. if you needed to switch it on you’d be in serious trouble (remember, metabolism is all the processes that your body goes through to maintain itself every day).

This is why I think metabolism has been such a talked about topic in popular magazines and the fitness world in general. It’s become the scapegoat for fat loss not happening. Which brings me on to my next point.

So, if it’s not my metabolism, what can I actually do to lose body fat?

By this point, you’re probably wondering what you can do with all of this information. In short, you can relax. Your metabolism is more than likely not the issue if you can’t lose body fat and it is WAY more likely something you can actually measure and change to get the results you want.

What can happen when you try to lose body fat is that it gets harder and harder the more you lose. You drop calorie intake over time, your activity level becomes harder to maintain and your hunger levels tend to go up.

What we need to do is put some strategies in place to make sure the following things can happen…

You have some form of measure of your activity levels, food intake and training.

There are a few things I would consider useful, easily measured and valuable here. First off, keeping a track of steps you do each day. This allows you to keep a tab on activity without having to put too much thought into it. Next up, you’re going to have to measure portion sizes in one way or another. Whether that’s having a set of guidelines or rules for meals, set meal plans, tracking calories or measuring portions…that depends on you really. Lastly, keeping track of training is going to make sure you can keep progressing forward. Think of training like the ‘shaping your body’ part of fat loss.

You are prepared to deal with hunger when it inevitably increases

Preparing for hunger is very individual. Some people just don’t seem to get hungry. However, if you’re anything like me, hunger hangs around like a bad smell. There are a few things that can really help though.

First off is having some high volume, low calorie, easy to cook foods at hand. Think cauliflower, broccoli, squash, swede, low fat Greek yoghurt, berries, apples, melon, egg whites, frozen mixed veg, tins of tuna/salmon, pre-cooked lean meat/eggs, whey protein to give a few examples. Sometimes having low calorie or zero calorie items can help, that’s your choice…but best not to build every meal around a giant bowl of jelly.

Secondly, is identifying WHEN in the day you are most hungry. Without even taking a look at any population studies, I can say with confidence that most people I have met who have struggled with losing body fat are much more likely to over eat on an evening. This is usually because: tired from work, can’t be arsed to cook from scratch, have made a lot of decisions and don’t want to have to think about food and as such end up eating anything or everything in sight, have high energy convenience foods readily available in the house.

If you know WHEN you are going to be the hungriest, you can either 1. Save some of your calories or eat your biggest meal then (this could be the time where you have something you just want because it’s delicious- plan it, stick to the said amount and enjoy it without guilt) or 2. Plan to have some of those options stated above at hand to make sure you can make something that isn’t too high in calories but still fills you up!

If you plan on going for a large deficit…make sure to take a ‘break’ from low calories every now and again, so you can mentally recover and go again.

Maintenance is the lost skill of fat loss. In my eyes, this is the biggest reason people aren’t successful with fat loss. It’s well worth making time for when you’ll take your foot off the gas and bring calorie intake up to maintenance levels again for a short time. This can be entirely personal, however I’m a big fan of trying to push for at least 6-8 weeks then taking a week or so at maintenance before going again. That being said, it can be variable from person to person.

A cautionary note though, if you’re taking breaks so often you’re only spending every other week in a deficit…you’re going to be trying to lose fat for a long time. Breaks can also depend on how low you go with your calories. If you’re only aiming for a small deficit, you might not feel the need. But remember the trade off your making- a longer time trying to lose body fat. Larger deficits mean a shorter time losing body fat, but as you can imagine are harder to sustain and so call for the occasional break. We’re all adults here, so it’s your call on the trade-off.

Following on from the last point… consider the things you will need long term to maintain your fat loss.

The biggest successes I’ve seen with fat loss being maintained are with those people who carry on doing the things that got them there, just at a lower intensity. Think of this like a temperature gauge. Turn that sucker up high and you’re going to have to turn it down sooner, because you’re going to get hotter quicker. You’ve got above where you’ve wanted faster, but you’ve been sweating like a beast and you’re having to cool down a bit to reach that ideal temperature. On the other hand, you could increase the temperature gradually, take longer to get there and deal with a slower process of warming up. Either way, when you get there you’ll have to maintain the same temperature on the gauge.

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