Eliminating carbs and sugar from a diet may help with weight loss in the short-term but does it actually effect fat loss?
Sugar-free and ketogenic (more commonly called ‘keto’) diets have gained significant popularity in recent years as part of a broader trend towards low-carbohydrate and low-sugar eating. In following these diets, individuals are eliminating their intake of foods and beverages linked to obesity, diabetes, and other chronic conditions, usually with the intention to lose weight, in general.
The keto diet originally gained attention in the medical community as a treatment for epilepsy in the early 20th century. However, its popularity as a weight loss program surged in the 2010s, particularly with the widespread popularity of Atkins brand. Keto diets emphasize high fat, moderate protein, and very low carbohydrate intake, pushing the body into a state of ketosis (hence the name), where the body burns fat for fuel, leading to weight loss and other potential health benefits.
Both diets have been marketed as effective ways to lose weight, improve energy levels, and enhance overall health. However, they are often criticized for being difficult to sustain long-term and the potential for nutrient deficiencies associated when following them long-term. Despite these concerns, both approaches remain very popular, and a recent study aimed to specifically measure the effects of a ketogenic diet and a low-free-sugar diet on energy metabolism, fat loss, and overall health.
Public health guidelines often recommend limiting free sugar intake to less than 5% of total daily energy intake. Earlier studies, including one conducted by the current research team, have not consistently demonstrated significant changes in energy balance within one full day (24 hours) of restricting sugar. Results have shown, instead, that while reducing free sugars may lower overall energy intake, its direct effects on fat loss are more complex.
For the most recent study, healthy adults were randomly placed into three groups: a ketogenic diet group, a low-free-sugar diet group, and a control group with moderate sugar intake. The study lasted three months, during which time the participants’ dietary intake, energy expenditure, and other health markers were closely monitored.
Both the ketogenic and low-free-sugar groups reported significantly reduced carbohydrate intake, with carbohydrates accounting for less than 8% and 5% of total energy, respectively. The control group, which maintained moderate sugar intake, gained 18% of their energy from free sugars. Ultimately, at the end of the 12 weeks, participants in both intervention groups experienced fat loss, primarily due to reduced energy intake.
The study revealed some key differences between the two dietary approaches, however. The low-free-sugar group had lower total cholesterol levels and low-density lipoprotein cholesterol (LDL-C) levels compared to the control group. Additionally, in the ketogenic group, the respiratory exchange ratio (RER) decreased, indicating a shift away from carbohydrate metabolism towards fat utilization for energy. This group experienced some unhealthy metabolic changes, such as impaired glucose tolerance and increased levels of the inflammatory marker C-reactive protein (CRP), at certain points during the study. Interestingly, the ketogenic diet also led to shifts in the gut microbiome, with an increased presence of specific bacteria like Bifidobacterium adolescentis and Planococcus. By week 12, many of the observed changes had diminished, despite participants continuing to follow the diet and maintain ketosis.
This study highlights that while restricting free sugars or carbohydrates can lead to reduced energy intake and fat loss, the benefits for metabolic health are less clear. The ketogenic diet, while effective for weight loss, may also lead to unfavorable changes in glucose tolerance, inflammatory markers, and gut microbiome diversity. As with any new diet, individual responses may vary, and it’s important for individuals to check with their healthcare provider for any safety issues ahead of time.
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Ketogenic vs. low-sugar diet: Study reveals distinct metabolic effects and fat loss benefits
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