Why There’s No Such Thing As A Diet for Fast Metabolism.

Why There’s No Such Thing As A Diet for Fast Metabolism.

Hey Maria here. You won’t believe the amount of trash that comes up when you google for things like “foods that speed up metabolism!”

I saw even “organic food” marketed as a way to increase your metabolism. I mean, all the facepalms in the world are not going to be enough for this level of stupid.
foods that speed up metabolism

Going through the Google search results was painful really.

  • If you understand how metabolism works I suggest you avoid googling to save yourself from the pain.
  • If you don’t know how metabolism works I also recommend you skip the googling or you’re in danger of being led in a completely wrong direction: Similar to detox diet plans, a fast metabolism diet sounds good in theory but does not deliver, no matter “how clean” you eat.

But the good news is there’s a legit way to increase your metabolism. This knowledge will come in very handy especially if you want to lose weight OR avoid having to eat less and less as you age because “your metabolism slows down” and you “gain weight more easily.”

Tommy Cole, an exercise scientist, nutrition nerd, and personal trainer will review the research. Enter Tommy.


Before I entered the fitness and nutrition world, I couldn’t work out why some of my friends never seemed to add an ounce of fat to their toned physique no matter what kind of junk they scoffed down their gob.

Biscuits, chips, burgers, the lot; it never seemed to add an inch to their waist like it did to me.

And it didn’t make any sense because I was doing everything I could to follow a “fast metabolism diet”:

  • I was eating plenty of “clean foods” that wouldn’t drag my metabolism down like the junk they ate
  • I made sure I had my meals at the right time of day to maximize the amount of fat I burnt
  • And I ate little and often to keep my metabolic flame roaring

But it didn’t seem to make a scrap of difference.

Now I realise that what I was doing was completely wrong though.

And what I thought was helping me achieve the body I wanted was in actual fact doing the complete opposite.

It wasn’t a fast metabolism diet at all, and the reality is that I was missing the forest for the trees, focusing on boosting my metabolism in completely the wrong way.

Let me explain:

Foods that speed up metabolism: Even your morning croissant boosts your metabolism.

First things first, all diets, whether they’re jam pack with McDonalds, poptarts, or salad, will boost your metabolism.

This is simply because all food and drink you consume needs to be absorbed, processed, and in some cases, stored. No surprises there. What you might not have thought of previously is that this processing of food/drink requires energy and therefore increases the number of Calories you burn.

Yes, that means that even your morning croissant, biscuit with your tea, or post dinner Ben and Jerry’s will increase your metabolism:

  • This metabolism boosting effect of food/drink is known as the thermic effect of feeding (1,2); one of the three components of metabolism along with,
  • resting metabolic rate, and
  • activity thermogenesis (for simplicities sake, think of the words thermic and thermogenesis as synonymous to Calorie burning).

I like to think of the thermic (Calorie burning) effect of feeding as similar to how you must invest money in a business to make money; Calories must be invested in digestion to gain Calories and nutrients from food.

So when you read about metabolism boosting foods or diets for fast metabolism the main focus is on increasing the thermic effect of feeding component of your metabolism.

However, while it all sounds very sexy, and it’d be really neat if by choosing different foods we could really have a significant effect on our metabolism, this is simply NOT how it works.

Instead, it’s another part of our metabolism, activity thermogenesis that you’d need to focus on if boosting your metabolism is a goal of yours.

But before we get into what to do to boost your metabolism, let’s first review the rage about metabolism boosting foods.

Foods that speed up metabolism: less processed equals higher metabolism; protein and fiber burn more. But don’t get overexcited just yet.

Now, I know what you’re thinking: surely a big ass chicken salad will boost your metabolism more than a pack of skittles?

Well yes, it probably will.

Whilst it’s true that technically cookies, chocolate, and any other so called “fake food” will boost your metabolism, it’s no surprise that they shouldn’t make up a big part of your diet when trying to trim down.

Besides being jam packed with Calories, they won’t increase your metabolic rate as much as their less processed counterparts.

And as a generalisation, whole and minimally processed foods will increase your metabolism to a greater extent. This is because they typically contain more fiber, bioactives (like antioxidants), and other nutrients that require a greater enzyme action, churning, and processing in general after they’re consumed (5).

In fact, a study in 2010 found that a sandwich made with multi-grain bread and cheddar cheese increased participants’ metabolism by 47% more than one made with white bread and processed cheese (5).

fast metabolism diet
Graph Credit: Barr and Wright (2010). Postprandial energy expenditure in whole-food and processed-food meals: implications for daily energy expenditure. Food & nutrition research, 54(1), 5144.

This result was most likely down to a combo of the multi-grain sandwiches’ greater protein and fibre content.

You see, of the dietary macronutrients (protein, carbohydrates, fat, and alcohol):

  • Protein has the greatest thermic/Calorie burning effect weighing in at 25-30%. That means that if you were to consume 100 Calories worth of protein, your net gain of Calories would be 70-75, as 25-30 Calories would be burnt to digest and process it.
  • Alcohol also has a similar thermic effect (10-30%)
  • Carbohydrate and fat have a 6-8% and 2-3% thermic effect respectively, meaning they burn fewer Calories to be processed by your body (2,4).

So simply put, a food or diet high in protein (around 2g/kg bodyweight) will boost your metabolism more so than something lower in protein (2). The same goes for foods with lots of roughage, fibre, and nutrients, as it means they’ll take longer and demand more effort from your body to be broken down and processed (5).

“What about fat burners, hot food, and caffeine? I’ve heard they ramp up your metabolism too?”

Well yes, sort of.

You see, when you consume certain spices, herbs, and ingredients (eg: capsaicin in peppers, caffeine in coffee, and compounds found in green tea) the activity of your sympathetic nervous system increases.

This may ramp up your heart and breathing rate, increase your utilisation of energy stores, and as anyone who’s taken on a spicy vindaloo will know, leave you fanning away your curry induced sweat. All these effects may lead to a slight increase in your metabolism and overall daily energy expenditure (16).

Current research suggests that the boost your metabolism gets from these three compounds may be up to a max of around 4%, which means you might burn an extra 50-80 or so Calories a day with their help (16-19).

So there are indeed metabolism boosting foods! Nope – don’t get overexcited just yet! While this is the research that will be offered to you to make you follow a fast metabolism diet when you put this knowledge in context of how things work, you’ll immediately see why consuming all the metabolism-boosting foods in the world won’t do a great deal to move the needle with your metabolism.

Before I go on an explain that, let me bust another myth: that eating small and frequent meals has a metabolism effect.

I’m sorry, but eating frequent small meals does not boost your metabolism.

“Ok, so when I eat, my metabolism goes up. That means I should eat little and often to constantly spike my metabolism, right?”

Unfortunately, no; it doesn’t work like that.

Whilst it’s often said that eating lots of small meals will “stoke your metabolic fire”, that’s as much of a myth as my love for the treadmill, which I haven’t touched in years.

You see, whilst all food will boost your metabolism to some degree, the size of the meal plays a big role in its metabolism boosting effects, with large meals having a greater thermic effect than smaller ones.

fast metabolism diet

This makes a lot of sense if you think about the following for a minute:

Take yourself back to the last time you felt full. I’m talking the type of fullness you get post Christmas dinner. You know, yoga-ball-food-baby-full. Pretty uncomfortable wasn’t it?

Imagine how much time and effort it took for that food baby to be broken down, processed, and absorbed by your body. It would have required a lot of energy, that’s for sure. You might have been so full that you even had to go out for a stroll to help your belly with the digestion.

Now compare that to the effort it would take to quickly scoff down and process a small bowl of cereal. In comparison, the effort and energy required from your body to process this small meal would be much less.

The point I’m getting at here is that the increase in metabolism as a result of a meal is proportional to its size, with larger meals having a greater thermic effect than smaller ones (7).

That means meal frequency isn’t all that important when it comes to your metabolism and it is the total amount of food that you eat over the course of the day that matters instead (8).

For example, let’s say that one day you decide to eat lots of little meals because your friend told you it would keep your metabolic fire roaring. Each meal would increase your metabolic rate slightly, adding up to maybe 200 Calories burnt from the thermic effect of feeding over the course of the day.

If you were then to eat fewer, but larger meals the next day, each one would increase your metabolic rate to a greater degree than the individual meals the previous day. Provided you were to eat the same total amount of food over the course of the day, the larger meal size would compensate for the lower meal frequency, adding up to the same daily boost in metabolism as the previous day’s meal pattern.

So in a nutshell, it is the total amount of food over the course of the day that determines how much your metabolism increases from eating, not the frequency of your meals.

Now with all that science out of the way, let’s get back to the chicken salad vs skittles example I mentioned at the beginning.

Fast Metabolism Diet: A salad will boost your metabolism more than candy – by a whooping 5 calories!

To keep things realistic, we’re going to take a standard serving size of both. So 55g of skittles vs a pre made supermarket chicken salad. Here’s the nutritional breakdown:

fast metabolism diet

Straight off the bat, you might think the skittles would trump the salad simply based on its Calorie content. Whilst it’s true that the greater the Calorie content of a food, the more likely it will boost your metabolism more, you have to look deeper and consider what else the food/meal is made up of.

As you can see, the skittles are mostly carbs, whereas the salad is more mixed with a much higher protein content. By now you should be pretty clued up on the fact that protein will ramp up your metabolism more so than any of the other macronutrients. In this instance, this higher protein content of the salad is a game changer and gives it greater metabolism boosting properties than the skittles despite its lower Calorie content.

In fact, after a quick bit of maths, I worked out that your body would burn in the region of 15 Calories to process the skittles, but over 20 for the chicken salad. Whilst these calculations just give an estimation, they demonstrate just how important the macronutrient composition of a food is when it comes to its effect on your body.

With that said, the difference is only 5-6 Calories. If we were to extrapolate this to a full day of eating 1500-2000 Calories from solely salad or skittles, that would equate to around 50 more Calories burnt by eating just salad; not exactly anything to call home about, which leads me on to a very important point.

Now I know it may seem as though I’ve bigged up the metabolism boosting properties of some foods here, but whilst it’s true that certain foods do increase your metabolism more than others, in the grand scheme of things, the effect that food has on your metabolism is quite small.

In fact, it’s hardly worth worrying about any sort of “fast metabolism diet” whatsoever.

Why A “Fast Metabolism Diet” or metabolism-boosting foods sound good in theory but don’t deliver.

You know I explained how the thermic effect of the different macronutrients ranges from around 2-30%?

Well, in the context of a healthy diet with a mix of protein, carbohydrates, and fat, the overall thermic effect of feeding generally accounts for roughly 10% of your daily energy expenditure. As an example, if you were to burn 2000 Calories per day, the thermic effect of feeding would account for around 200 Calories of that.

Now remember the thermic effect of feeding was only of three components of our metabolism. If we compare it to them, you’ll see that’s a pretty miniscule figure:

  • Your resting metabolic rate typically accounts for 50-60% of the Calories you burn. That’s 1000-1200 Calories using the same example above.
  • Non exercise activity thermogenesis and exercise activity thermogenesis (together referred to as activity thermogenesis) can vary massively between individuals because as you well know, some people are more active than others. For a standard sedentary person, activity thermogenesis might add up to around 30-40% of the Calories burnt per day. 670-800 Calories using the example above.

foods that speed up metabolism

Because the thermic effect of feeding has such a minor effect on your total daily energy expenditure, there really isn’t such thing as a fast metabolism diet, and you can’t really change your metabolism in any meaningful way by eating particular foods, or by following some fancy meal schedule.

Simply eating a balanced diet will do the job. Yeah, boring; I know.

So from a dietary perspective, you should focus primarily on the basics if your waistline is of concern; not because they’ll ramp up your metabolism to new heights, but because the science says they’ll help you drop the pounds:

  • Eat a moderate to high amount of protein (6, 15).
  • Consume mostly nutrient dense foods like fruit, legumes, veg, lean meats, nuts, seeds, wholegrains, and dairy (9,10).
  • Consume a moderate deficit of Calories (ie: roughly 20% below the amount you need to maintain your weight). This will maximize the amount of food you can eat while dropping weight at a rate of around 1-2 lb per week (6).

Whatever you choose to do to create this caloric deficit, make sure you don’t find it terrible; pushing yourself to adhere to a regimen that is either too difficult to implement or too punishing may help you lose weight  in the short-term but it won’t help with keeping weight off in the long-term.

Have you ever fallen for those “foods that speed up your metabolism?” What did you try? Tell us about your experience in the comments.

Click here to view the sources referenced in this article.