Fact or Fiction: Do Carbs Make You Fat?

Carbohydrates have long been regarded as a primary cause of fat gain, but is that actually the truth?

While carbohydrates are a primary source of energy for most of us, if consumed in excess, they can certainly lead to weight and fat gain, but fortunately for all of us, this doesn’t happen to the extent that most think.

In this article, I’ll touch on what carbohydrates are, their purpose and how they can result in excess weight gain. Afterwards, I provide best practices for adjusting your carb intake based on your energy requirements.

What Are Carbohydrates?

Before getting directly into whether or not carbohydrates can make you fat, you first need to understand what carbohydrates are, what their purpose is and finally, what contributes to carbs being stored as body fat.

Carbohydrates are essentially chains of sugar molecules of differing length. Very short chain or single molecules of sugar, otherwise known as glucose, are considered to be “simple sugars.” This includes ingredients like table sugar, rice, honey and even fructose found in fruits.

On the other hand, you have what are known as complex carbohydrates, which have much longer chains of sugar molecules and are a bit more difficult to digest. This includes ingredients like starchy vegetables, some oats, whole grain products and beans (1).

Eventually however, all of these carbohydrates once ingested, are broken down to their simplest form, known as glucose.

Glucose is a simple sugar that our body derives its main energy source known as ATP. When carbohydrates are consumed, they all have the fate of being broken down into glucose but the complexity of their structures determine how quickly this occurs.

What Role Do Carbohydrates Play Once Ingested?

As briefly mentioned, when consumed, carbohydrates of all sorts are broken down into glucose, which can then enter the blood stream to be used for a number of different purposes.

The first fate of carbohydrate, or glucose for that matter is to begin metabolism and be used immediately through a process known as glycolysis. This would happen if you were active, such as during a workout, and you ingested a sugary drink. This glucose is metabolized to provide ATP, to push you through the workout (2).

Second, this glucose can be shuttled towards different tissues such as organs like the liver and even muscle, where it’s transformed into what is known as glycogen, the stored version of glucose. Essentially, it’s a stockpile of glucose just incase you need it for further activity or even survival (3).

Third and lastly, this glucose can be transported to fat cells, stored and converted into triglyceride or body fat, through a process known as De Novo Lipogenesis (4).

While this process does occur, it’s actually less common than most think and really only becomes an issue if carbohydrate intake is extremely high and activity level is very low. But we’ll get into that a bit later.

Carbohydrate Intake & Activity Level

The main issue with the fear of carbohydrate leading to fat gain is that there is some truth to the theory, just not in the way that most people think.

Your energy balance, or the ratio of the calories that you consume, relative to the amount of energy your body burns through activity on a day-to-day basis largely regulates bodyweight changes (5).

If you’re consuming more calories than you’re expending, you’re creating what is known as a positive energy balance, which leads to weight gain. Essentially, you’re ingesting more energy than you need, so the body stores it for later use.

Considering that carbohydrates have calorie amounts, if you end up consuming more calories from carbohydrate sources than are required by your activity level, you can expect this to contribute to overall weight gain.

At this point, the process of De Novo Lipogenesis occurs, where glucose in the blood is shuttled towards fat cells, stored and then converted into triglyceride (4).

Essentially, it’s important to remember that it’s not necessarily the carbohydrates themselves causing the weight gain. Rather, the weight gain is due to consuming far more carbohydrates and thus, calories than are required.

Use Carb-Cycling To Manage Your Carbohydrate Intake

Based on the previous information, it’s safe to say that overall, carbohydrates really only contribute to weight and fat gain, if their consumed in a greater amount than is actually required by the body for energy and storage.

Since this may be the case, it’s suggested that you consider using what is known as carb-cycling; a method that allows you to manipulate your carbohydrate intake, based on your energy requirements and activity level each day.

For example, if carbohydrate can become and issue when consumed in large amounts, it makes sense to adjust your carb intake based on how active you are. On days that you’re very active or have a high volume training session like a leg day, you consume your highest amount of carbohydrate.

On days that your training volume is lower or even on rest days, you consume your lowest amount of carbohydrates. Essentially, this method allows you to increase or curtail carb consumption based on activity.

Additionally, you can even use this method with equal calorie amounts or if you’re attempting to lose body fat, you can also manipulate total calorie amounts, in addition to carbohydrate.

Here’s a week example of how to pair your carb consumption with your activity level:

  • Day 1: High Volume Leg Day – High Carb Day
  • Day 2: Rest Day – Low Carb Day
  • Day 3: Upper Body, Moderate Volume – Moderate Carb Day
  • Day 4: High Volume Leg Day – High Carb Day
  • Day 5: Rest Day – Low Carb Day
  • Day 6: High Volume Leg Day – High Carb Day
  • Day 7: High Volume Arm Day – High Carb Day

Fact or Fiction: Do Carbs Make You Fat?

Overall, it’s safe to say that carbohydrates themselves don’t directly contribute to weight gain, but they certainly can if you’re consuming them in excess.

Essentially, the factor deciding whether or not carbohydrates get stored as body fat is activity level. If activity level is very low, yet carb intake is high, it’s possible that those carbohydrates could eventually contribute to fat and weight gain.

Based on this information, if you’re concerned about carbohydrates and fat gain, consider using a carb-cycling approach that allows you to manipulate carb intake, based on daily activity level.


  1. Simple vs Complex Carbs. (n.d.). Retrieved June 21, 2017, from http://www.diabetes.co.uk/nutrition/simple-carbs-vs-complex-carbs.html
  2. Brooks, G. A. (2010). What does glycolysis make and why is it important?.
  3. Ivy, J. L. (2001). Dietary strategies to promote glycogen synthesis after exercise. Canadian Journal of Applied Physiology, 26(S1), S236-S245.
  4. Acheson, K. J., Schutz, Y., Bessard, T., Anantharaman, K. R. I. S. H. N. A., Flatt, J. P., & Jequier, E. (1988). Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man. The American journal of clinical nutrition, 48(2), 240-247.
  5. Spiegelman, B. M., & Flier, J. S. (2001). Obesity and the regulation of energy balance. Cell, 104(4), 531-543.