Why Calorie Needs Can Vary Between Individuals

By Aadam | May 22, 2024

People waste an inordinate amount of time and mental energy worrying about how many calories someone else is eating compared to how much they’re eating.

Fit_bro99 posts about how he’s maintaining his weight while eating 3000 calories per day. And your sorry ass can’t even lose fat eating half that much.

You accidentally tell Susan from accounts how much you’re eating, and she responds with, WOW, THAT’S SO LOW and later forwards you an article on starvation mode (god bless your fucking soul, Susan).

And now you’re all kinds of confused. Instead of actually doing something, you spend your days going down rabbit holes and getting even more confused. In the words of the great philosopher DJ Khaled: Congratulations, you played yourself.

In reality, the number of calories you need to eat to lose fat (or gain muscle) will be different to someone else. Yes, even if that person seems fairly similar to you on paper.

Here are two reasons why.

1. Everyone burns different amounts of energy

On the surface, this seems fairly obvious. I mean, a 6’2” male who weighs 200 lbs will burn more calories than a 5’4 female who weighs 130 lbs.

This is true broadly speaking. However, people can burn drastically different amounts of calories at any given body weight.

The image below is taken from ​a 2021 study​ in which researchers examined the total daily energy expenditure (TDEE) of ~6,400 people worldwide. 1

As you would expect, the heavier the individual, the higher their energy expenditure. But even at the same weight, there’s substantial variability in TDEE. I currently weigh about 80 kg (170 lbs), and my TDEE is ~2500 kcals, which is around the average mark in the image above. But at the same weight, another male could be burning almost 6000 kcals. The same is true for females. If a female maintains her weight on 2000 kcals, she could lose a pound per week while eating 1500 kcals. Conversely, if another female maintains her weight on 1500 kcals, then she might need to eat 1100 kcals to lose a pound per week.

Quick aside: The ‘pound per week’ is totally arbitrary, and it’s not how I recommend setting the deficit. I’m just using it for the sake of simplicity.

As such, we can’t make blanket statements about how much someone should and shouldn’t eat without considering the individual’s context. For instance, the study referenced above noted–

There is considerable metabolic variation among individuals, with TEE and its components varying more than ± 20% even when controlling for fat free mass, fat mass, sex, and age.

Meaning two people could appear similar (based on height, weight, sex, and age), but their caloric needs could be vastly different.

It’s also worth remembering that it’s all relative. If my daily energy expenditure is 3000 kcals/day and I’m dieting on 1500 kcals, that’s a very aggressive deficit of 50% (you gon’ fuck around and find out). However, if I’m only burning 1900 kcals/day, dieting on 1500 kcals represents a pretty moderate deficit of 20%, which is a fairly common recommendation.

2. People respond differently to a calorie deficit

At some point during a diet, you’re going to need to make adjustments to your caloric intake to account for ​metabolic adaptation​––i.e. the reductions that occur in the metabolism with ongoing weight loss.

But here’s the thing: Some people experience more metabolic adaptation than others.

In one study, researchers had a bunch of young, healthy men eat in a 50% deficit for three weeks, followed by a 50% surplus for two weeks. The average reduction in their metabolic rate during the deficit was ~100 kcals, but there was a lot of inter-individual variability (see image below). Some of the men hardly saw a decrease in their metabolism, while others saw a pretty steep drop. 2

Individuals who experience more metabolic adaptation tend to lose less weight than those who don’t experience as much. 3

In practical terms, this means two people could start a diet eating the same number of calories, but the person who experiences more metabolic adaptation would need to eat fewer calories to achieve the same amount of weight loss as the other.

Ok, I lied––there’s actually three reasons.

3. Energy compensation

This topic can tread even deeper into the realm of “WOW, this shit is a mindfuck” when we factor in things like ​energy compensation​.

In an ideal world, more physical activity would increase your daily energy expenditure in a 1:1 fashion. That is, if you burned 500 calories during a run, your daily energy expenditure would also increase by 500 calories (what’s referred to as the additive energy model).

But it’s not that simple.

If you’re pretty sedentary and increase your physical activity levels, you will see an increase in energy expenditure. But if you’re already pretty active, doing more exercise won’t result in a linear increase in energy expenditure because the body will reduce other components of your metabolism to ‘constrain’ total energy expenditure within a narrow range.

Moreover, the likelihood of this compensation is higher in an energy deficit compared to when you’re eating at maintenance or a surplus.

So, let’s say you’re fairly active and create a 500-calorie deficit based on your current activity levels. If you experience a higher degree of energy compensation, that 500-calorie deficit might only be a 250-calorie deficit. So, on paper, you should be losing a pound per week. But in reality, you’re only losing half a pound per week due to energy compensation. Consequently, you might need to adjust your intake further to account for this.

Conversely, someone who isn’t that active won’t experience as much energy compensation, so they could lose weight by eating a bit more while doing less exercise.

Again, on paper, this would be super counterintuitive––that person is doing more exercise, you might think, but eating less and potentially losing a bit slower than someone who isn’t as active. It’s also easy to see why that active person might assume there’s something wrong with their metabolism or be accused of lying about how much they’re eating, even if they’re not.

Speaking of which–

All of this is based on the assumption you’re tracking your food intake accurately

Oh, you thought I wasn’t going to mention this? You thought wrong.

More often than not, when someone’s dieting on fewer calories than they think is reasonable, it’s because they’re ​not tracking as accurately as they think​ they are.

For instance, let’s say you need to eat 2000 kcals to lose fat. But you’re forgetting to log 200 kcals. In your mind, you’re eating 2000 kcals. In reality, you’re actually eating 2200 kcals. The result? Your progress is slower than it should be.

After a week or two, you might decide to reduce your calories by 200 to try and get things moving. Totally reasonable. But you’re still forgetting to account for those 200 additional kcals. So you think you’re eating 1800 kcals when you’re actually eating 2000 kcals. Progress is still slower than it should be.

Frustrated, you decide to shave off another 200 kcals––now, you’re logging 1600 kcals, but in reality, you’re actually eating 1800 kcals (assuming a consistent 200 kcal discrepancy). You’re finally in a deficit, progress picks up, and you’re losing the right amount of weight each week.

In this example, the individual thought they needed to eat 1600 kcals to lose fat, but if they were tracking accurately, they could have lost fat by eating 1800 kcals.

Now, if you’re consistently misreporting by the same amount each day, that’s not a huge deal––as you continue to adjust your intake, you’ll eventually fall into a deficit.

However, consider a situation where someone’s misreporting fluctuates wildly each day. They misreport by 100 kcals on one day, 600 kcals on another, and 300 kcals the next, etc. Let’s say, on average, they’re misreporting by 500 kcals each day. They could have lost fat eating 2000 kcals/day, but due to the misreporting, they’re eating 1500 kcals/day––cue metabolic damage or starvation mode, and the point where I bash my head repeatedly on my desk.

I hope this illustrates how, in the real world, things are a lot more nuanced.

You might be able to lose fat by eating a bit more than someone who, on the surface, seems fairly similar to you. Or, you might need to eat less than someone who’s fairly similar to you.

Instead of worrying about how much someone else is eating, focus on what you need to do to make progress. Ultimately, that’s the only thing you have control over.

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