How Our Metabolism Works

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“[Metabolism] is so much more than just a buzzword in the health world.”

Your body depends on energy from foods in order to grow, develop, reproduce and support other life-sustaining functions. Metabolism is a term we often hear tossed around when people talk about losing weight or dieting, yet it is so much more than just a buzzword in the health world. It is what is used to describe all the physical and chemical reactions taking place within our bodies. It’s what turns the food we eat into the energy that lets our heart, brain and body operate. Inside of us, a myriad of important chemical reactions are happening that take the food we eat and turn it into this energy.

Think of your body as a busy city, and in this city, enzymes are like the hardworking folks who keep everything running smoothly. They make sure all the energy-generating processes happen like they should. These enzymes “listen” to hormones, which are like the supervisors telling them how fast or slow to work. These hormones include insulin, which helps to get the sugar into our cells and control the sugar levels in our blood, adrenaline, which gets us ready to move fast in a hurry, and GLP-1, which tells our brain when we are full and should stop eating.

Hormones produced by the thyroid gland tell our body how much energy to use when we’re not active and just chilling out. This resting energy consumption is our basal metabolic rate (BMR), which is important because it is the energy our body uses for crucial functions like keeping our brain running even when we’re asleep, keeping warm, fixing cells, and breathing, even when we’re not moving around.

“Someone who’s very active and exercises daily or has a physically-demanding job will need more calories in order to maintain their weight compared to someone with low activity levels.”

Everyone’s metabolism is a bit different, and it’s not set in stone. It depends on variables such as age, diet, sex, activity levels, genetics and health conditions. Even when we eat, we get our metabolism working because our body needs energy to break down the food.

The energy required for physical movements, such as exercise, varies depending on your activity levels. Someone who’s very active and exercises daily or has a physically-demanding job will need more calories in order to maintain their weight compared to someone with low activity levels.

There are two types of metabolic reactions: catabolic and anabolic reactions. Catabolic reactions involve the breakdown of larger molecules into smaller molecules. These types of reactions usually release energy. An example is when our bodies digest food (fat, protein and carbohydrates), giving us energy. Anabolic reactions form larger molecules from smaller molecules. These reactions use energy – such as building muscle or bone mass.

When we get up and move, it’s like giving our metabolism a big cheer to keep going. Building muscles through things like lifting weights is great because muscles use more energy than fat, even when we’re sitting still. Keeping our bodies moving is really important as we get older because our metabolism tends to slow down a bit.

But it’s not just about how old we are, or how big our muscles are. The genes we get from our mom and dad can make our metabolism faster or slower, which can affect how easily we might gain or lose weight. But the way we live – the things we do every day – can really make a difference in how well our metabolism works.

“Protein digestion requires 10-30% of the energy content of the ingested protein, while carbohydrates and fats require 0-10%.”

What we eat is like the fuel for our body’s engine. Foods that have a lot of protein are like putting a big log on a fire – they burn long and strong. But eating a lot of sugary stuff is like using paper to start a fire – it burns out fast. Protein digestion requires 10-30% of the energy content of the ingested protein, while carbohydrates and fats require 0-10%. In other words, your body burns more calories digesting protein than it does digesting carbs or fats.

Sometimes, though, our bodies have a tough time with metabolism because of health problems. Things like thyroid problems can either make our metabolism go too slow or too fast, which can make us gain or lose weight when we don’t want to. Other health problems like Cushing’s disease or being really sick can mess with our metabolism too.

But here’s the good news – there’s a lot we can do to keep the fire of our metabolism burning bright. Eating a variety of different healthy foods gives our body what it needs to keep our metabolism going strong. Moving around and building muscle is like adding fuel to the fire, keeping it burning well. Getting enough sleep and not letting stress take over is also super important for keeping our army of hormones doing their job right.

“To help our metabolism do its best, it’s all about balance. We don’t need to do extreme diets or workout like crazy.”

Understanding metabolism is like looking at a map of how our body uses energy. It’s seeing how all the different things we do – from eating to sleeping to running around – all add up to keep our energy balanced.

To help our metabolism do its best, it’s all about balance. We don’t need to do extreme diets or workout like crazy. It’s just about making good choices every day, like drinking plenty of water, because almost everything our body does to make energy needs water. Or eating a protein rich diet.

Choosing foods that are good for us, like lots of fruits, veggies, lean meats, and nuts, can help our metabolism work better. A study looking at 304 women aged 18-50, with obesity or in the overweight BMI category who ate a largely Mediterranean style diet, consisting of vegetables, fruits, nuts, eggs, lean meats and legumes had significantly higher BMRs than those who followed diets high in ultra-processed foods, sugar and fats.

Beyond your diet, don’t forget about taking care of our mental health. When we’re really stressed and flood our body with stress hormones, it can mess up the way our metabolism works. Doing things to relax, like breathing exercises or hanging out with friends, can help a lot.

At the end of the day, metabolism is all about how we turn what we eat into the energy we use to live our lives. We’re all part of this story, and we can all make choices that help us feel good and full of energy. By knowing what affects our metabolism and doing things to help it out, we can keep our body’s energy engine running smooth and steady.

This post was inspired by reading Jillian Kubala’s article on Health, which can be found here.

E. Dylan Mayer is a graduate from the University of Colorado at Boulder, with a major in Neuroscience and minor in Business. He also holds a Master’s Degree in Nutrition from Columbia University.

This article was reviewed and approved by Emeran Mayer, MD