Low-Sugar Diet Effectively Reduces Cholesterol, Aids in Fat Loss

Dylan Thompson, PhD

Credit: X.com

A diet low in free sugar—such as added sugars and those found in fruit, smoothies, vegetable juices, and purées—was shown to significantly reduce cholesterol in LDL particles and help to reduce fat mass, leading investigators to believe it may be a better dietary choice for overall cardiometabolic health.1

In contrast, the ketogenic diet raised cholesterol levels and increased apolipoprotein B (apoB), the protein responsible for plaque buildup in the arteries, in addition to decreasing beneficial bacteria in the gut.

Current dietary guidelines suggest restricting free sugars almost entirely from the diet based on self-reported energy intake. Therefore, there is a need to confirm whether this restriction can alter energy intake without self-report methods.²

“To date, no study has directly measured physical activity energy expenditure (PAEE) or objectively determined energy intake in response to longer-term free-sugar restriction to infer efficacy or effectiveness of recommendations,” wrote a team of investigators from the University of Bath. “Furthermore, the impact of free-sugar restriction and associated body composition changes on metabolism and gut microbiome is currently unclear.”

The current study, published in Cell Reports Medicine, included 53 healthy adult subjects who were randomized to a diet restricting dietary free sugars (LOWSUG) or overall carbohydrates (LOWCHO). These were then compared with a control group in which patients could eat a moderate amount of sugar and carbohydrates (MODSUG). The primary endpoint was to characterize the effects of restricting either sugar or carbohydrates on free-living PAEE over a 12-week span. Investigators believed both the ketogenic diet and the restricted sugar diet would reduce physical activity compared with the control cohort.

Cardiometabolic responses and other mechanisms were assessed by measuring the gut microbiome composition, fasting and postprandial metabolism, appetite-related hormones, and skeletal muscle and adipose tissue phenotypes.

Eighteen patients were placed in the MODSUG cohort, 17 were randomized to the LOWSUG group, and 18 were in the ketogenic (LOWCHO) diet group. Patients randomized to MODSUG reported consuming approximately 18% of energy from free sugars, compared with < 5% in the LOWSUG group. The LOWCHO group were only allowed to consume < 8% of their energy from total carbohydrates.

Surprisingly, neither sugar nor carbohydrate restriction significantly changed physical activity or any other energy expenditure factors. However, they did reduce energy intake which led to weight loss. These diets exhibited different systemic lipoprotein, lipid, and amino acid responses.

In addition to the benefits of lowered fat and cholesterol, sugar restriction did not significantly alter the composition of the gut microbiome. Conversely, the ketogenic diet decreased levels of Bifidobacteria, the beneficial bacteria found in probiotics that aids in the production of b vitamins while inhibiting pathogens and harmful bacteria.

While the ketogenic LOWCHO diet reduced fasting and nocturnal glycemia, it also encourages glucose intolerance and suppresses the postprandial lactate responses.

Investigators noted that although physical activity and body weight were not mentioned in meetings with participants, nor did they know physical activity was the primary outcome of the study, it is possible their previous beliefs about the correlation between diets, exercise, and body weight may have impacted the responses. Another limitation was the reduced statistical power for the primary outcome due to the number of dropouts and COVID-19 mitigation, thus creating a smaller sample population.

“The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone,” said co-investigator Dylan Thompson, PhD, professor of Human Physiology in the Department for Health at the University of Bath and Co-Director of the Centre for Nutrition, Exercise and Metabolism (CNEM). “In contrast, sugar restriction supports government guidelines for reducing free sugar intake, promoting fat loss without apparen­­t negative health impacts.”

References

1. ^{Hengist A, Davies RG, Walhin JP, et al. Ketogenic diet but not free-sugar restriction alters glucose tolerance, lipid metabolism, peripheral tissue phenotype, and gut microbiome: RCT. Cell Rep Med. Published online August 1, 2024. doi:10.1016/j.xcrm.2024.101667}
2. ^{Erickson J., Sadeghirad B., Lytvyn L., Slavin J., Johnston B.C. The Scientific Basis of Guideline Recommendations on Sugar Intake: A Systematic Review. Ann. Intern. Med. 2017; 166: 257-267https://doi.org/10.7326/M16-2020}