What influence do carbs have on metabolism?

September 24, 2020

What influence do carbs have on metabolism?

Studies have suggested that low-carbohydrate diets increase your metabolism compared to high-carbohydrate diets, which may help you lose more weight. 

We take a look at how food affects your metabolism, why the type of carbohydrate you eat matters, and how you can harness your biology to maintain a healthy weight.

In this post, we cover:

  • How carbohydrates impact your metabolism
  • Why the quality of your carbs matter
  • How you can hack your unique biology to achieve a healthy weight and stay healthy

How your metabolism works

Everything your body does requires energy - this process of energy generation and burning is known as metabolism. Even digesting your food burns energy - in other words, you gotta spend money to make money! 

If your body needs more energy than you can generate from the food you eat, then it will start to burn body fat and, eventually, muscle.

The amount of energy released from your food depends on what you eat and how your body works.

Different types of carbohydrate have different effects on metabolism

‘Carbohydrates’ is a broad umbrella term used to describe different sugars, starches, and fibers found in many of the foods we eat. They are found in fruit, vegetables, legumes (beans and pulses), dairy, and grains.

All of these different types of carbohydrates are digested differently and can have varying effects on your metabolism. 

How does a low-carb diet affect your metabolism?

A recent study from scientists at Harvard University compared the energy expenditure of people on low-carbohydrate diets compared with people in moderate or high-carbohydrate diets. 

They found that people on lower carbohydrate diets tended to burn more energy, so should we all be on low-carb diets to maximize our metabolisms? 

We say no because while these approaches may work for some people, they don’t work for everyone. Here’s why.

In the Harvard study, the scientists only asked people in the study to control the amount of carbohydrate and the percentage of sugar they ate. They didn’t control the type or quality of carbohydrates. 

This approach misses out a key truth about carbs: carbs aren’t all the same. And, importantly, neither are people. 

Our PREDICT study shows that even identical twins can have very different responses to the same foods, with the same amount and type of carbohydrate. So picking a low-carb diet is no guarantee that it’s right for your unique metabolism.

The DIETFITS study conducted by our expert Christopher Gardner, Ph.D., which we discussed here, showed that when you stick to high-quality food sources, there isn’t much difference between eating a low or high carbohydrate diet when it comes to weight loss. Both diets work well for some people, but not for others. 

Why the quality of your carbohydrate matters 

When we eat food, we aren’t just eating a pile of separate nutrients. Food, and particularly whole foods, have complex structures that have to be broken down for our body to access the energy within, known as the food matrix. To access the sugar in a banana, our body first has to break down the fibrous structures of the fruit, which makes it very different from simply eating spoonfuls of sugar. 

Generally, the more processed, refined, or ‘low quality’ our foods are, the easier they are to digest. 

So if you eat a high-carbohydrate diet that consists of lots of highly-refined carbohydrates like white bread and white rice, you’ll extract more energy from that food than someone who eats the same amount of carbohydrate from ‘high-quality’ sources like legumes, whole intact grains, and fruit. 

Your metabolism is unique

Even when we take the type, structure, and quality of carbohydrates into account, we are still missing an essential factor: you. 

Our food is very complicated, and so are each of us! We each have our own unique microbiome, genetics, and responses to food, which vary from person to person.

As our PREDICT study shows, one person might be able to digest a particular food quickly and release the energy inside easily, but another person might have to expend much more time and energy during the same process. 

If the same food can influence the metabolism of different people in different ways, then whether you burn more energy on a low-carbohydrate or high-carbohydrate diet is likely to be personal to you. 

Our at-home test, based on the same tests used in our research, is designed to help you better understand your biology and discover which foods are best for you.

Recapping carbs and metabolism

  • Some foods are harder to digest and require more energy to release the nutrients inside than others. 
  • Some carbohydrate-based foods such as simple sugars and refined grains are easy to digest, meaning you burn fewer calories during digestion
  • Others contain lots of fiber and complex carbohydrates that your body needs to break down before using, burning energy in the process
  • Precisely which foods increase your metabolism, helping you to burn body fat, depends on your unique biology


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