Apr 11

Do you have a slow metabolism?

This is a serious question, ask many people and its a resounding yes. I was going to talk about whether calories counted today, but I though people would just come up with excuses as to why they are different and how they have a slow metabolism, so I thought I’d debunk that first.


What we normally hear is someone who’s overweight or struggles to lose weight say, “its really tough for me to lose weight, I’ve got a really slow metabolism”. The question here then is, do these people who say they have “slow metabolisms” actually have them? And has 2 3rds of the UK and USA’s populations metabolisms slowed down over the last 40 years contributing to our obesity epdiemic, or is it, something to do with the 20% increase in calories we’ve had from eating more food over the last 40 years? (1)


Generally we see larger people saying they have slower metabolisms than thin people, well the interesting thing about this is, the bigger you are, the more cells you have and the more energy you require for each of those cells to function.


Also if people have more body-fat, although it doesn’t burn a lot of calories, excess body-fat is metabolically active and does burn calories, so the fatter someone gets, the more calories they burn at rest, larger people will also burn more calories from exercise, just because of the fact they have more weight to shift, and I can attest to this after running with a 30kg weighted vest, its bloody hard work.


But don’t take my word for any of this, the studies are very clear, as people get heavier, their metabolisms go up, and it doesn’t matter if its lean muscle or excess fat, if people are heavier, they have a faster metabolism than people who are lighter, also as people gain weight, they generally gain 33% of the weight as muscle anyway. (2)


As you can see from the graph, the heavier a person, the higher their metabolism, of course some people do have slightly higher metabolisms than others, but that will mainly be to do with different levels of lean body-mass as muscle does burn more calories than fat, but the main point is, the heaviest people have the highest metabolisms.

Of course the above study was comparing different people, what happens if you “gain weight easily” do you have a slower metabolism then? And does your metabolism stay low or does it get faster because you’ve got heavier?


Well interestingly, in overfeeding studies, where scientists find peoples resting energy expenditure, and then go beyond this by getting them to eat more, they continuously find people gain weight and have an increase in metabolisms, which makes sense really, you eat to much, you get fatter and your body increases its metabolism to try and burn off the excess weight and because your body it simply has more cells using energy now. (3,4)


In a study on non obese young individuals, who according to most people can eat what they like, were subjected to overfeeding and gained an average of 8kg’s 2rd of which was fat mass and one 1rd muscle all had an increase in metabolism.


In another study when subjects gained 10% extra body-weight, they had a total energy expenditure increase of almost 500 calories, and when they lost 10% in body-weight from the original weight, they had almost a 300 calorie decrease as you can see below.


As you can see, the studies show, the ultimate predictor of your metabolism is how much you weigh, this also explains why larger people lose weight faster, its not necessarily that they have more weight to lose, its that they have a higher metabolism, meaning they burn more calories at rest and when exercising. It also explains why peoples weight-loss starts to slow down as they get lighter, they get slower metabolisms and this is not because they have been dieting for to long, its simply because they weigh-less and burn less calories daily than when they were fatter.


So the moral of the story is, if you are overweight, you don’t have a slow metabolism, you actually have a faster metabolism than someone smaller than you, the real problem is much more likely you eat to much of the wrong food or even to much of the right food, don’t exercise enough or reward your exercise efforts with food.


Before we end this, you are probably thinking what about your hormones, people have told probably told you the reason your overweight is because you have a hormone problem and need to sort out your thyroid, contro insulin levels etc… and you’ll lose weight.


First I stand by my point that over the last 40 years we’ve started to consume 20% more calories a day and thats why we are overweight, not because everyone has hormone issues, but i’ll give people the benefit of the doubt.


So in a study comparing people with subclincal hypothyroidism, so these are people with real thyroid issues here, not someone getting you to fill in a sheet and then saying you have thyroid issues and blaming all your excess weight on that and telling you they have the magic cure.


So if anyone has slow metabolisms from thyroid problems, it would be these people, yet when compared to controls of the same weight and age, we find they have metabolisms which are exactly the same as controls. (5)

















Next the other myth we often hear is, insulin is making you fat and your high insulin levels will be making you store more calories as fat, yet when we look at people with normal glucose tolerance, impaired glucose tolerance and type 2 diabetics, we see the diabetics have highest resting metabolic rates and then the people with impaired glucose tolerance and finally the normal glucose tolerance have the lowest resting metabolic rates.(6)

I won’t go into the myth that insulin makes you fat today as that myth will take some explaining and killing, but in summary although hormones are an extremely important part of health and wellbeing, they are also extremely complex and every cell in the human body requires energy and always will until it dies, so even if one organ is not working at 100% efficiency, this does not mean the whole bodies metabolism will come to a halt, the only true way for that to happen would be for cells to start dying.


The real reason people think they have slow metabolism is often because they underestimate how much food they eat and overestimate the amount of exercise they do, for example a study looking at obese people who claimed to have slow metabolisms were actually underestimating food intake by 47% and overestimating exercise levels by 51%. (7)

So now you know that when someone says they can help fix your broken metabolism, its very likely they are lying, they might be able to help improve your eating, lifestyle and exercise habits to lose weight, but they won’t be fixing your metabolism because its not broken.


Stay tuned and I’ll debunk the myth about calories and whether they count next time.


2 pings

  1. Do Calories Count – Part Two » The Place For Information on Rapid Fat-Loss, Body Transformation & Improved Performance | The Place For Information on Rapid Fat-Loss, Body Transformation & Improved Performance

    […] as I pointed out on my article about slow metabolism, is much more likely reason why we’ve gained weight than as many authors claim, which is […]

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