How to Speed Up Metabolism: Understanding Metabolism for Body Composition

1 October 2022
Andy Tait

I have written this because I wish I had known this information when I first started training and went through my own weight loss journey. I was focusing on how hard and how much I could train instead of the other, more important principles I will explain in this article. 

Applying the concepts of this article helped me lose and maintain a healthy weight while providing me with the energy I need to live my life.

This article will give you an overview of how to boost your metabolism and how it affects your body composition.

Body composition is what your body is made up of, in the fitness industry we mean the ratio of lean body mass vs fat mass.

If you are worried that you have a medical condition like Hypothyroidism or Polycystic Ovarian Syndrome (PCOS) affecting your metabolism then you should consult your doctor.

Do you want to know how to speed up your metabolism? Let’s jump in!

What is Metabolism?

Your metabolism is responsible for all cellular activity within your body.  It is the amount of energy your body burns/requires throughout the day, also known as your total daily energy expenditure (TDEE).

Your metabolism converts your food into energy and building blocks for your body while removing excess cellular waste.

Your body will preferably get the energy to fuel you through food. However, when food intake is limited for whatever reason, your body will break down its own tissue (fat or muscle) to provide the necessary calories for your body to keep functioning. When the latter is the case, your body is smart and knows that it needs to slow down the rate at which it is burning energy/calories.

Your metabolism is unique to you and constantly changing day-to-day as your body requires more or less energy. Some people have a higher rate of metabolism and therefore burn more calories, while others have a lower metabolic rate and burn fewer calories. This is largely due to genetics, age and gender, but there are some aspects of your metabolism that you can control.

Many people ask the question “What metabolism do you need to lose weight?” Well, that isn’t the right question because you have your own unique metabolism and the choices you make will have an impact on it.

Do you have a slow metabolism and find it difficult to lose weight? Or, do you have a fast metabolism and struggle to gain weight? Let’s find out why…

Energy (Calories) In

This is the energy that you put into your body through food and drink. This energy can be measured in calories. Although energy coming into the body technically isn’t your “metabolism”, it’s important to discuss because it has a direct impact on the amount of energy your body uses.

What is A Calorie?

A calorie is a measurement of energy that your food provides you. It is dictated by the macronutrients that are in the foods you eat.

Each macronutrient contains a certain amount of energy for the body. For example, 1 gram of the following macronutrients is equal to a certain number of calories.

1g Protein = 4 calories

1g Fat = 9 calories

1g Carbohydrates = 4 calories

1g Alcohol = 7 calories

Although they all provide a set number of calories, their effect on the body can differ per macronutrient

Your food also contains micronutrients which are the vitamins and minerals your body needs to function properly. Although these are necessary, they do not provide energy for your body.

In very simple terms, if you feed your body with more calories than you use, then it will store that energy within the body. This will either be stored as glycogen in the liver or muscle tissue from carbohydrates, as fat within the body, or used to build extra muscle tissue just so long as you’re doing the correct resistance training (read more about this in Do Carbs Make You Gain Weight?). Your body is storing the energy so that it can draw from it in the future when energy coming into the body is scarce.

Note that the body can only store so many carbohydrates within the liver and muscle. Therefore when those macronutrients have been used by the body and there is an excess, they will be converted into fat stores. Excess fat intake will also be stored however it will not need to go through the same conversion process.

As you read through the rest of this article you will see that calories consumed from food and calories burned by the body are intrinsically linked to each other.

Do you want to know how to boost your metabolism? Let’s learn how that’s possible.


Energy (Calories Out)

This is the process by which your body is using the energy provided as fuel for movement, digestion, and storage of calories. This is your metabolism.

This is where things get both interesting and complex. This is because every calorie going into your body (or anyone else’s) through food, is the same amount of energy. But the rate at which your body uses that energy is at a completely different rate from anyone else. This is why your metabolic rate will differ from everyone else’s.


Total Daily Energy Expenditure Pie Graph.png



Energy out can be summarised into 4 criteria.

  • Basal Metabolic Rate (BMR)

  • Non-Exercise Activity Thermogenesis (NEAT)

  • Exercise Activity Thermogenesis (EAT)

  • Thermogenic Effect of Food (TEF)

These 4 are what’s known as your Total Daily Energy Expenditure (TDEE). These are the processes by which energy is used.

Basal or Resting Metabolic Rate (BMR)

Also known as Resting Metabolic Rate (RMR), BMR determines how much energy is required to keep your vital bodily functions working at complete rest. Resting Metabolic Rate includes breathing, circulating blood and other cellular activity. It is influenced by your genetics, sex, height, weight, age, current body composition (lean tissue), and previous eating habits.

Non-Exercise Activity Thermogenesis (NEAT)

This is the amount of energy used for daily activity not including purposeful exercise. This is the second biggest influencing factor on the total energy used within a day. This includes everything from playing with your pet to doing the housework or even fidgeting.

Exercise Activity Thermogenesis (EAT)

This is the amount of energy used up within an exercise session. This would include weight training, yoga, indoor cycling, etc. Notice that this is only around 10% of TDEE. Exercise, specifically lifting weights, plays a huge part in building muscle when in a calorie surplus and maintaining muscle when in a calorie deficit.

Thermogenic Effect of Food (TEF)

TEF is the amount of energy it takes to digest your food and accounts for around 5% of your TDEE. An example of this would be that it takes more energy to digest protein than it does to digest other macronutrients. This is often a benefit of a higher protein diet.

Increasing Your Metabolism (Energy Out)

Increasing your metabolism means increasing the number of calories your body burns daily.


Basal Metabolic Rate (BMR)

As your BMR is dictated mostly by age, gender, genetics etc, there’s only so much control you have over this aspect of your metabolism. The biggest thing that you can do to improve it would be to increase lean mass (muscle).

Your muscular system requires a lot of energy just to maintain itself. However, if you’re going through a weight gain phase to increase metabolism then ideally it would be muscle because stored fat doesn’t require energy to maintain itself, but muscle does.

Non-Exercise Activity Thermogenesis (NEAT)

You can see from the image that non-exercise activity has a larger role to play than exercise activity when it comes to calorie expenditure. This means that although you think burning calories is related to gym training or exercise, you burn many more calories in the general day-to-day movement and activities that you do.

Increasing daily movement and non-exercise activities, like walking to work, vacuuming, etc, will increase your metabolic rate. This aspect of your metabolism plays an important role in determining how many calories your body burns. Understandably the 23 hours you spend outside of the gym will outweigh the 1 hour spent in the gym. This is very underrated when it comes to burning calories. Many people get frustrated when they see no weight-loss progress after they have been killing themselves in the gym, but it’s often the case that they’re training so hard that they subconsciously reduce activity outside of the gym.

Generally being heavier will increase your calories burned through movement and exercise as it requires more energy to move a heavy body in comparison to a lighter one. This means that when on a diet and trying to lose weight, as you get lighter you will burn fewer calories. This can cause the rate at which you lose weight to slow down unless you reassess your calorie intake.

NEAT is also the aspect that is most influenced by the amount we eat. If you’re trying to lose weight then subconsciously you will move less as your body is trying to conserve energy. On the flip side, if you eat more your body will subconsciously move more to burn the excess energy. This can happen without thinking about it. This doesn’t mean you should eat more to lose weight or eat less for weight gain. You still need to be in a caloric deficit or surplus to lose or gain respectively.

A tool that can be useful when trying to lose weight is a step counter. This is to combat the reduction in movement from lack of energy. Set yourself an average daily step target for the week and then try to hit that number on top of your training.

Exercise Activity Thermogenesis (EAT)

This is the most obvious and sometimes overrated aspect of metabolism and “burned calories”.

Of course, exercise will burn calories and can be a great tool for weight loss and is a must for building muscle.

You need to think about what kind of training you’re doing and ask yourself, is that the best way to achieve your goal? If you want to build muscle then lifting weights is a no-brainer.

When it comes to weight loss, however, there seems to be this understanding that more exercise (cardio) is better. Endurance training indeed burns a lot of calories. However, it does make you lighter and will likely burn muscle tissue as well as fat. This will decrease your BMR and therefore in the long term will decrease metabolism.

Now, I’m not suggesting that you do no cardio. There’s no denying that cardio is good for you, but you can have too much of a good thing. Especially when trying to lose weight.




If you want to become leaner and more defined then I highly suggest that you focus your attention on strength and hypertrophy (building muscle) training. This will ensure that you’re maintaining if not gaining muscle mass while in a caloric deficit.

Focus on creating a calorie deficit through nutrition and daily movement (NEAT), and then supplement that with strength training and a small amount of cardio for its physical and mental health benefits.

Something else that’s worth a mention is cardio burns more fat and weight training uses stored carbohydrates as fuel. This is because fat is the primary source of low-intensity activity and cardio. While carbs/glycogen is the primary fuel for higher-intensity activity and weight training.

So why not just do cardio? Good question, on top of what was mentioned above with a reduction in muscle mass and BMR, burned fat doesn’t necessarily equate to long-term fat loss. If you burn more fat, you will store more fat. If you burn more glycogen, you will store more glycogen. So weight loss comes down to an overall daily calorie deficit as opposed to just being in the “fat-burning zone” during exercise.

This is why I highly suggest that you do resistance training for your daily exercise and then you can burn fat the rest of the day for your other activities.


Thermogenic Effect of Food (TEF)

This is the last and smallest factor when it comes to your metabolism.

This is the caloric cost it takes to digest your food. Understandably, it requires energy to digest and distribute your food and nutrients. It was previously believed that eating 6 small meals per day would increase your metabolism. However, it’s not the meal frequency that dictates the increase in metabolism, but the number of calories consumed throughout the day in total.

Therefore this means that you will have the same metabolic response from eating the same food in 3 larger meals as you would in 6 smaller meals.

One thing that will impact TEF is protein intake. Protein requires more energy to break down and therefore will increase the thermic effect of food. This doesn’t mean that you should only eat protein. For someone that trains, you should aim for 0.8-1g of protein per 1lb of body weight. More on this in my Weight-Loss Article.


Metabolic Adaptation

Metabolic adaptation is where your metabolic rate adapts over time to meet your current lifestyle and diet.

If you’re in a daily calorie surplus for a prolonged period then your body’s metabolic rate will gradually increase over time. This has a small part to do with increased muscle and/or body weight, metabolizing extra food, and more energy for training. However, the biggest factor that is impacted is NEAT. As mentioned above, you will subconsciously move and fidget more throughout the day. This is an attempt for the body to use up excess energy to keep you at homeostasis.

The same can be said if you’re trying to lose weight and are in a calorie deficit for a prolonged period. As you progress further into your diet your metabolism will adapt. Your metabolism will decrease because your body isn’t digesting as much food, and your workouts will start to suffer as you don’t have the same amount of energy. Your body will move and fidget less subconsciously, all as an attempt to conserve energy. Not only that but when you do move and exercise you will burn fewer calories because you’re now lighter and potentially (god forbid) have less muscle to maintain.

You will often see bodybuilders either struggle to eat the amount of food they need to while on a “bulk”, or be super hungry the leaner they get on a “cut”. This is the body’s way of signalling that it wants to get back to a level to which it is accustomed, often known as the “set” or “settling point”.

This is an issue for people that have a relatively petite frame that wishes to increase their size. It can be so difficult for them to put on any weight, let alone increase their muscle mass.

This is also problematic when attempting to lose weight. If you’ve been chronically dieting for months/years then you will likely see a decrease in your metabolic rate as a result. Because you’re always in a calorie deficit, or because you yoyo between an extreme calorie deficit and binge eating, your metabolism adapts by reducing your calorie expenditure to ensure that you’re conserving as much energy as possible. This is because, from an evolutionary standpoint, your body thinks that food is scarce and is trying to keep you alive.

This would be a time when people use tools like a “reverse diet” or “recovery diet”. This is where, each week, you would gradually increase your daily calories by 50-100 in an effort to restore your metabolism to what it should be.

This would very gradually undo some of the negative aspects of the diet you’ve been on. It will give you more energy and you will subconsciously start to move more therefore you will be able to maintain your weight while feeling more energetic and eating more calories. This is a topic for another post but it can be beneficial if you’re trying to lose weight. The higher your metabolism, the more you can eat to maintain your weight. This makes losing weight somewhat easier as you’re able to eat more food and feel more satiated. I’m not suggesting by any means that there will be no amount of hunger while in a calorie deficit, but it can make the process less daunting.



I wanted to write this to help you understand the full picture when it comes to body composition and metabolism.

Maybe you do have a “slow metabolism”, either from your genetics, age, frame size or metabolic adaptation. However, many things are in your control. For example daily movement and activity with the addition of resistance training.

Your body is a very complex and clever system. When you’re restricting food intake it will draw upon its own tissue for the fuel needed to support itself, all while reducing calorie expenditure in an attempt to keep you alive.

I often see people lean on a “slow metabolism” as an excuse for not losing weight when there are plenty of things they could be doing to increase calorie expenditure. This can often lead people to look for “hacks” and “quick fixes” in an attempt to increase their metabolic rate.

Let me tell you that there’s no amount of jumping in freezing water, eating chillies, or drinking apple cider vinegar that will lead to any significant increase in metabolism. Trust me, I’ve tried it all.

To increase your metabolism you can:

  • Increase muscle mass

  • Move more throughout the day. Walk to work instead of taking the bus.

  • Exercise 3-6 times per week with an emphasis on resistance training with added cardio.

  • Eat a high-protein diet (1g per lb of body weight)

  • Don’t be in a calorie deficit for long periods of time. When you are in a caloric deficit, don’t be too restrictive.

This is a lot of information to take in. I’m sure you have many questions, if you do, please leave a comment below and I will respond to you.

Thanks for reading,


Aka “CoachTaiters”

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