Low carb = superior results?

One of the most common nutrition misconceptions I come across in my practice is the belief that low carbohydrate diets are superior for fat loss. While reducing carbohydrate intake when dieting can potentially assist you in a variety of ways, it is by no means the most effective protocol for fat loss. Before we look at the studies investigating low carbohydrate diets and fat loss, we must first understand how this popular misconception began.

History of low carbohydrate diets

The history of low carbohydrate dieting can be traced back to 1863 with the release of Letter on Copulence. In the pamphlet, William Banting discusses his experience of undergoing a low carbohydrate diet. At the time, Banting was a severely obese patient who was suffering from multiple health issues. His medical provider at the time, Dr. William Harvey went on to prescribe that he eliminate starch, sugar, beer, and potatoes and instead aim for meat, fish, vegetables. The switch in his nutrition worked and Banting’s various health issues improved. Since then, numerous individuals over the last 150 years have been recommending low carb approaches with the most famous being Dr. Robert Atkins. The basis of most low carbohydrate diet advocates centers around the carbohydrate insulin hypothesis (CIH). Before we talk about CIH though, let’s first take a look at the role of insulin.

Carbohydrate Insulin Hypothesis

Insulin is a hormone released by the pancreas. It’s purpose is to aid in the storage of nutrients (mostly glucose) into various cells (muscle, fat, and liver). It is assumed that carbohydrate rich foods stimulate the highest insulin response. CIH is based around the idea that higher carbohydrate diets lead to a higher secretion of insulin. This then leads to something called insulin resistance. Insulin resistance occurs when the cells become less sensitive to the absorption of nutrients. This inefficiency of absorption then leads to persistent hunger and overeating. Chronic overeating can lead to obesity. Makes sense right? Unfortunately, that’s not how it works. Let me explain.

CIH works under the assumption that carbohydrates solely cause the highest secretions of insulin. Do you know what else can cause a large secretion of insulin? Whey Protein! That’s right! One of the most bio-available protein sources with numerous health benefits can cause a larger secretion of insulin than white bread (4).  This not only applies to whey protein, but many other protein sources as well. Another study compared two meals of differing composition but of equal calories (1). One meal had 75 g of carbohydrates and 75 grams of protein while the other had 125 g of carbohydrate and 21 g of protein. They found that the higher protein meal had a slightly higher yet not statistically significant insulin response compared to the high carbohydrate meal.

As you can see, protein can have just as much of an effect on insulin levels as carbohydrates. Many studies have documented the benefits of higher protein diets on health and body composition so saying insulin is the problem is not correct. Now, let’s take a look at the what the research has to say about low carb diets.

What does the research say?

Let’s take a look at two different studies looking at low carb diets and weight loss. A study done by Leibel et al. compared several isocaloric diets (15% protein, 15%-85% carbohydrate, and 0%-70% fat) in a controlled environment (3). They found that caloric restriction, not macronutrient composition determine weight loss.

Golay et al. carried out a similar study (2). They investigated the effects of a hypo-caloric, protein matched diet with differing macronutrient composition and it’s effects on weight loss in 68 patients over 12 weeks. They split the patients into two groups, one with 25% carbohydrate and the other with 45% carbohydrate. The study found that there were no significant differences in fat loss and lean mass loss. Several other studies on the matter found similar results when comparing low carb and high carb diets.

What is the best diet for fat loss?

In summary, the argument for low carbohydrate diets being superior for fat loss is not supported by the current scientific research. Does that mean that low carbohydrate dieting is wrong? Not at all. The studies above showed both high carb and low carb diets can be effective for weight loss. It ultimately comes down to personal preference. I have many clients who enjoy eating a lower carbohydrate diet and are successful with their goals. Also, keep in mind that when most people venture on a low carbohydrate diet they typically improve their food quality and they eliminate many of the foods that they overindulge in. That right there is the main recipe for success.

To sum it all up, the best diet for fat loss is the one that you can adhere to. For more information or a more personalized nutrition plan, feel free to contact us today!




  1. Boelsma, E., Brink, E. J., Stafleu, A., & Hendriks, H. F. (2010). Measures of postprandial wellness after single intake of two protein–carbohydrate meals. Appetite, 54(3), 456-464. doi:10.1016/j.appet.2009.12.014
  2. Golay A, et al Weight-loss with low or high carbohydrate diet. Int J Obes Relat Metab Disord. (1996)
  3. Leibel RL, et al Energy intake required to maintain body weight is not affected by wide variation in diet composition. Am J Clin Nutr. (1992)
  4. Nilsson M, et al Glycemia and insulinemia in healthy subjects after lactoseequivalent meals of milk and other food proteins: the role of plasma amino acids and incretins Am J Clin Nutr (2004)

Written by: Jesus Hernandez RDN, LD

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