Metabolism in a nutshell [infographic!]

Updated: Jul 31, 2019

We all have that friend - the one who can eat what they like and doesn't seem to put on an ounce of fat. They'll explain that they have a 'fast' metabolism. Then there's others who have a 'slow' or 'sluggish' metabolism and grumble that they put on a couple of kilos if they even look at a slice of cake.

Metabolism in a nutshell

Your metabolism refers to all of the chemical reactions that happen inside the human body to keep you alive and functioning. It is responsible for how your body uses nutrients to refuel, rebuild and repair. Your metabolic rate refers to your body's daily energy expenditure. It tells you how fast or slow your body uses calories as a unit of energy.

'Calories in, calories out' ... What is actually happening here?

Let's simplify this. There are four broad components of your Total Energy Expenditure (TEE).

Total Energy Expenditure (TEE) =

  1. Basal Metabolic Rate (BMR) (for a critical analysis of the utility of BMR calculators, read my blog BMR calculators - A useful tool or wildly inaccurate?)

  2. Thermic Effect of Food (TEF)

  3. Non-Exercise Activity Thermogenesis (NEAT)

  4. Exercise Activity Thermogenesis (EAT)

This infographic briefly outlines each component and indicates the proportion of calories that it contributes to your TEE.

Putting this into practice to boost your metabolism

If you look at the numbers, it's clear that the biggest components of our daily calorie expenditure are our BMR and our NEAT. Therefore, it makes sense to manipulate the variables that will influence our BMR and NEAT first. This is the practical and effective approach that Stan Efferding takes in 'The Vertical Diet' - his system prioritises optimising sleep, food, training and physical activity to boost a person's BMR and NEAT as the solution to accelerated fat loss and minimise metabolic adaptations.

I'm a flow chart geek, so if you're like me and like to see information in front of you, here's (another!) handy infographic that sets this out.

This translates into some practical steps that you can take to support your metabolism:

  1. Lift weights. Training to build muscle will not only create the shape you're after, it will also increase your BMR and cause your body to use more calories at rest. This can make it easier for you to lose fat and maintain a lean physique without the need to cull calories.

  2. Move your body. Keep active to capitalise on your NEAT potential. Think of this on a spectrum. You don't have to shift from sedentary office worker to walking 15 000 steps over night. This could be as simple as breaking prolonged sitting, getting out and about, or just standing and moving around for a break at work.

  3. Eat ample, real foods for a healthy metabolism, including adequate animal protein, nutrient-dense vegetables and fruits, and in general foods that your body can easily digest and absorb.

  4. Sleep like a king. Sleep is non-negotiable. Yes, even if you're hustling for fame and fortune. It's no longer cool to flaunt your sleep deprivation as a status symbol. Lack of sleep will disrupt your hormones, decrease your metabolic rate, sabotage your training and performance, and generally lead to a foggier, fatigued and unfocused you. Set your bed time, schedule at least 2 hours in the evening before bed to switch off your mind and body (and your phone, tablet, laptop and other gadgets) and stick to it.

Remember the bigger picture - hormones!

Hormonal balance is the gold standard of body composition and performance. Your body is really, really smart. Your metabolism constantly adapts and reacts to the signals you send it, and this include cues from inside your body and what's around you. For example, have you ever noticed that you can't simply restrict calories in a linear manner and expect your body to comply and seamlessly tap into its fat stores at a consistent rate? No chance. If there's a steady lack of fuel and nutrients available, your metabolism can shift into a more efficient mode so that it can perform its job while using less of its precious resources. This could lead to adaptations such as a sluggish digestion, a decrease in thyroid hormones to dampen your metabolic rate, or an increase in cortisol production due to putting the body under chronic stress.

Want to learn more?

There's a fantastic 'crash course' on YouTube called Metabolism and Nutrition: Part 1 and Part 2. It's incredibly thorough, yet easy to understand and delightfully quirky. (I'm not affiliated with this, I just think it's pretty clever.)

A disclaimer - this is a practical outline of human metabolism based on simple information that is freely available online and in most health and fitness books. I'm not a scientist and don't pretend to be one online, so please enjoy my information in the spirit that it's intended - as a practical, user-friendly synthesis of commonly accepted and broadly publicised information, for you to ponder and apply as desired to suit you and your body.