The Truth About Carbs, Insulin, and Weight Loss

... Can you actually eat carbs and lose weight?

Written by: Dr. Marc Morris Ph.D CSCS

For as long as it has existed, the nutrition and health industry has turned everyone against each other, from clients to coaches, about what causes fat loss. More importantly, they have constantly changed the culprits of weight gain. This has left people to wonder if they’re gaining weight because of carbs, processed foods, or calories in general.

Today we’re going to set the record straight on the true relationship between carbs, insulin, and weight loss.

Why Carbs are “Bad”

The people who want you to switch to a low-carb diet will tell you this is how you gain fat:

First, you eat carbohydrates, which increases the production of insulin by your pancreas. Insulin is the “storage hormone” that is released by carbs to regulate your blood glucose levels.

Then through a process called lipogenesis, which is when insulin increases fat storage, you begin to store fatty acids, which leads to fat gain.

This idea, which is called the “Carbohydrate-insulin Model,” is what has created the idea of “bad” foods, and has also made carbohydrates one of the most feared macronutrients. These ideas don’t show the full truth, so let’s debunk some of these myths.

Insulin and Fat Burning

When insulin levels rise, both fat storage (lipogenesis) and fat breakdown (lipolysis) occur simultaneously. However, your body prioritizes utilizing the new energy from elevated insulin levels rather than tapping into existing energy stores. Therefore, consuming a high amount of carbohydrates doesn't necessarily lead to fat gain. Although fat burning may be hindered, it doesn’t stop with the rise of insulin levels. Alongside insulin, other hormones like glucagon, epinephrine, and norepinephrine continue to promote fat breakdown despite elevated insulin levels.

The relationship between insulin and fat loss isn’t that simple, either. Insulin isn’t the only thing that promotes fat storage. An enzyme called Hormone-sensitive Lipase (HSL) exists in your fat cells to break it down. Insulin suppresses HSL, which might make it seem that insulin and carbohydrates are to blame for fat gain. However, dietary fat also suppresses HSL even when insulin is low. This makes it so you can’t break down fat, even when insulin is low.

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Insulin and Other Macronutrients

Carbohydrates aren’t the only macronutrients that stimulate insulin production. It may come as a surprise that protein stimulates insulin as well, and sometimes, just as much as carbohydrates. Most research shows that whey protein increases insulin the most, and whey protein is very low-carb.

Insulin, Appetite, and Metabolism

The common belief about insulin and hunger is that the higher your insulin levels, the more your body signals hunger. This is because insulin prompts the storage of fatty acids, reducing the energy (fatty acids/glucose) available for immediate use, which triggers hunger when levels drop. However, this theory contradicts observations, as many overweight individuals have elevated blood glucose and fatty acids despite their higher insulin levels.

Hunger isn’t regulated by just one hormone, either. Other hormones like Leptin, Cholecystokinin, Grehlin, and Glucoagon-like peptide 1 also play a role in your hunger. Even research shows that there has never been a strong link between insulin and hunger.

There are similar beliefs when it comes to insulin and metabolism. Low-carb dieters believe that by decreasing carbs, which in theory sends more energy to tissues like muscle, you’ll burn more energy. This hasn’t been consistently shown, however, and when different diets are compared using the same calories and protein intake, there hasn’t been a significant difference in weight loss or metabolism between diets.

What's the Best Diet?

Although low-carb diets might not be all they’re marketed to be, it doesn’t mean they don’t play a part in weight loss. You might find yourself being able to stick to a low-carb diet and seeing results from it. The issue isn’t about insulin, it’s how you’re going about your diet. One of the main reasons we see people starting a low-carb diet is they’re eating a lot of "junk" foods like cake, pizza, donuts, etc. Many if these foods are high in both carbs and fat, all while being highly processed. So while strictly going low-carb might not be the answer, you might find that limiting added sugar and ultra-processed foods is the way to go to improve your health and body composition.

Want to Learn More?

Watch the full video to learn the truth about carbs, insulin, and weight loss

Video >>