How Your Body Uses Carbs and Fats for Energy

February 20, 2018

How Your Body Uses Carbs and Fats for Energy

One of the timeless comparisons we are told growing up is that our body is like a machine. It needs fuel in order to power its daily functions. However, for a lot of people, that’s all they remember. What is the “fuel”? How does it power the “machine”? To put things in perspective: Carbohydrates, proteins and fats comprise 90% of the dry weight of the diet and 100% of its energy.1

For all three of these, energy is measured in “calories.” However, carbohydrates and fats stand apart from proteins. These two macronutrients are the subject of many misconceptions when it comes to health and nutrition. Let’s explain how your body converts these substances into energy.

Carbs for Energy
The real changes start in the small intestine for all three categories: protein, carbs and fats. This is where the majority of nutrients are extracted from the broken-down food we eat.

In the case of carbohydrates, they are broken into sugars. Generally, sugars end up being broken down into glucose, fructose and galactose. One thing that separates carbs from proteins and fats is the speed at which the body can process them. Certain carbohydrates can be converted into sugars and be present in your bloodstream for use as soon as 60 seconds after you eat. This is why athletes prefer to eat carb-heavy meals before longer workouts.

In essence, the body enters a state of glycolysis (for glucose) or fructolysis (for fructose) that converts these simple sugars into energy. Excess calories from sugar that don’t get used immediately are stored in the liver as glycogen. However, not all carbohydrates are equal. Keep this in mind.2

Fats for Energy
Fats have unfairly received a poor reputation over the years when it comes being a component of a healthy diet. For years, popular wisdom told us that fats were dangerous for our health and that they should be avoided as much as possible. Now we’re beginning to learn that fats are a critical component of total body wellness, and they provide energy to fuel our bodily processes .

When it comes to energy, fats are the slowest digesting of the three macronutrients, but they are also the most efficient. Every gram of dietary fat supplies the body with about 9 calories. To put things in perspective, protein and carbohydrates both supply 4 calories per gram.

In the intestine, fats are broken down into fatty acids and glycerol. These fatty acid chains are converted into energy via a process called beta-oxidation.

So, why the poor reputation? How does dietary fat become visible body fat? The answer lies with the energy that you don’t use.  The body likes to store excess calories for later, even if that later never comes. This leads to deposits in the abdomen, under the skin, and even in blood vessels and organs. Fat itself does not cause weight gain, but consuming more energy (in calories) than your body requires does. This is true regardless of whether the calories are coming from protein, carbohydrates or fats.

Where Can Things Go Wrong?
People sometimes blame carbohydrates and fats for various health issues. This Is preposterous. These two nutrients are vital sources of energy for our body! Carbohydrates and fats are not inherently unhealthy. The main cause behind many of these problems is overconsumption without doing anything to convert the glucose and fatty acids into energy. To make those conversions, the body responds to stimuli. For example, if you work out, the body takes note of this and starts turning those calories into the energy you need to complete your workout. Without any use, the calories become the deposits of fat or the elevated levels of sugar in the blood that we associate with being unhealthy.

It’s also important to understand that not every carbohydrate and fat source are the same. For example, simple carbohydrates, like table sugar, quickly increase the level of blood glucose. In many cases, these are also refined sugars, where most of the vitamins and minerals that come with the original product are stripped away. In essence, you have something that can provide energy quickly, but it has no nutritional value. That’s not the type of thing you want to build a diet around, especially if you aren’t exerting a lot of energy.4

By comparison, sweet potatoes or oatmeal are examples of carbohydrates which are digested more slowly, meaning they are less likely to end up as body fat, and they have plenty of healthy nutrients as well.

Not all fats are the same either. Many commercial foods that we consider fatty have “trans fats,” a man-made fat that has little nutritional value. However, there are plenty of other fatty foods that provide essential nutrients, like omega-3s from fish oil or plant-based fats from avocados or walnuts.5

In essence, this means that you need to make sure that you’re eating the right types of foods in the right amounts.

One thing that’s important to mention when it comes to digestion is enzymes. Enzymes play a quiet but crucial role, acting on the smaller molecules the digestive system creates from food to finally power all the body’s metabolic functions. Different enzymes correspond to different nutrients, like fats and lipase. In some cases, you can also use supplements that contain those all-important enzymes. In the case of lipase, Enzymedica’s Digest Gold™ and Lypo Gold™ are both great options to support optimal fat digestion.* Enzymedica VeggieGest™ is a fantastic option for the digestion of carbohydrates.*

Carbs and Fats For Energy
When it comes to nutrition, generally you want to adhere to two main principles: balance and quality. This means that you want to eat foods with good nutrient content, while also making sure that you get varied carbohydrate and fat intake. Checking with a doctor or nutritionist can do a lot to help you to find where you may be falling short, so you can develop healthy diet habits.


* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnosis, treat, prevent or cure any disease.


 1. Merck Manuals, Carbohydrates, Proteins, and Fats - Disorders Of Nutrition. http://www.merckmanuals.com/home/disorders-of-nutrition/overview-of-nutrition/carbohydrates,-proteins,-and-fats

2. Jéquier E. Carbohydrates as a source of energy. Am J Clin Nutr. 1994;59(3 Suppl):682S-685S.

3. Bjorntorp P. Importance of fat as a support nutrient for energy: Metabolism of athletes. J Sports Sci. 1991;9 Spec No:71-6.

4. Wylie-rosett J, Aebersold K, Conlon B, Isasi CR, Ostrovsky NW. Health effects of low-carbohydrate diets: Where should new research go?. Curr Diab Rep. 2013;13(2):271-8.

5. Hu FB. Are refined carbohydrates worse than saturated fat?. Am J Clin Nutr. 2010;91(6):1541-2.

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