Keto Diet & Weight Loss

The prevalence of obesity has increased dramatically over the last four decades. Obesity is a condition where high levels of fat accumulation can impair health. Recent numbers point to more than 40% of the United States (US) population having this condition. Ketogenic diets, defined as diets very low in carbohydrates or where energy is severely restricted, have become a popular weight loss tool. When the body is deprived of carbohydrates, the liver uses broken down fat to produce ketones as a source of energy. Ketones can provide up to 60% of the energy needed by the brain and spare muscle from being broken down for energy. This process is called ketosis. During ketosis, your body doesn't have enough carbohydrates to burn for energy. Instead, your body burns fat and makes things called ketones. These ketones can be used for fuel.

One of the problems of weight loss is that not only fat is lost, but also muscle. Since muscle requires more energy than fat, a loss of muscle leads to a greater reduction in your body’s energy needs. This may further hurt your body’s ability to be active. Some studies show that ketogenic diets can minimize, or prevent, the loss of muscle that usually comes with weight loss. They also show that β-hydroxybutyric acid (ßHB), the most important ketone body, seems to be involved. However, no study had investigated the association between the amount of ßHB circulating in the blood in individuals with obesity and changes in the amount of muscle following energy-restricted ketogenic diets. 

The aim of our study was to learn if the amount of ßHB in the blood was related to the changes in the amount of muscle after a ketogenic diet. We looked at both men and women with obesity. Our hypothesis was that greater amounts of ßHB in the blood would be associated with less muscle loss. Data from 199 adults with obesity (82 men and 117 women), who had undergone different ketogenic diets (with varying amounts of fat, protein, and carbohydrates), were combined for this analysis. The association between ßHB and changes in weight, fat, and muscle were investigated. 

Participants lost on average 15% of their initial body weight. This consisted of approximately 26 pounds of fat and 9 pounds of muscle. ßHB was not associated with muscle loss, but a higher ßHB was associated with more weight and fat loss. After considering age, sex, and body size, ßHB was found to be a predictor of both weight and fat loss following ketogenic diets. 

This is the first study investigating a potential relationship between the amount of ßHB in the blood (a marker of ketosis) and changes in the amount of muscle following energy-restricted ketogenic diets in men and women with obesity. We found that the level of ketosis was not associated with loss of muscle. However, the higher the level of ketosis, the greater the loss of weight and fat. This study is strengthened by the size and diversity of its sample. Our sample consisted of almost 200 individuals, both males and females, with a wide range of ages (18-65 years) and body sizes. 

These findings are important because they allow for the application of the results to people with obesity around the world, as well as those following a ketogenic diet. However, this study also has weaknesses that may have affected our results. The method used to measure changes in body composition (fat and muscle) did not account for the loss of body water seen after ketogenic diets. Additionally, the participants in our study used different diets, with different amounts of fat, protein, and carbohydrates. Instead, having each participant use the same diet would strengthen the results. Future studies should account for these things as it would provide more control to the experimentation.

Even though further studies are needed to confirm our findings and explore the mechanisms involved, individuals attempting to lose weight with ketogenic diets can expect to lose more weight and fat if they achieve higher levels of ketosis.

Written By: Dr. Catia Martins

Academic Editor: Neuroscientist

Non-Academic Editor: High Schooler

Original Paper

• Title: Association between ß-Hydroxybutyrate Plasma Concentrations after Hypocaloric Ketogenic Diets and Changes in Body Composition

• Journal: The Journal of Nutrition

• Date Published: 12 May 2023

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