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Researchers Raise Questions About Low-Carb Diets and Effects on LDL Cholesterol
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Results of the study showed an inverse relationship between BMI and LDL cholesterol changes for those who adopt a low-carbohydrate diet.
Low-carbohydrate diets have gained traction over the years, particularly for weight loss, but also for patients with type 2 diabetes and myriad other health conditions.1 However, several studies have shown that carbohydrate-restricted diets can cause an increase in low-density lipoprotein (LDL) cholesterol.2,3 Other conflicting reports have demonstrated a lipid-neutral effect4 or a reduction in LDL and total cholesterol.5
Foods included in a low-carb diet | Image credit: © aamulya | stock.adobe.com
Study results recently published in the American Journal of Clinical Nutrition sought to identify the source of this heterogeneity in the effects of low-carbohydrate diets on LDL cholesterol levels, with a focus on body mass index (BMI) as a potential factor.6
A group of researchers conducted a systematic review in which they sought out randomized controlled trials with a low-carbohydrate diet study arm that lasted at least 2 weeks and reported BMI. They excluded trials that had interventions with multiple components, such as exercise, or those that included pregnant or lactating women or children.Forty-one trials with 1379 participants and a mean intervention duration of 19.4 weeks met the inclusion criteria for the meta-analysis.6
Researchers created a meta-regression adjusted for saturated fat intake, carbohydrate intake, and weight changes to assess the effect of BMI on LDL cholesterol and accounted for 51.4% of the variability in LDL cholesterol. BMI was found to be strongly associated with LDL cholesterol changes, whereas saturated fat intake was weakly associated.6
Overall, the results of the study showed an inverse relationship between BMI and LDL cholesterol changes for those who adopt a low-carbohydrate diet.6 Leaner individuals typically experienced elevations in LDL cholesterol, whereas individuals with elevated BMI had either no change or a reduction in LDL cholesterol. The researchers proposed that net carbohydrate intake may affect LDL cholesterol by impacting lipoprotein trafficking, particularly in those individuals with lower adiposity, suggesting a phenotypic hypothesis of “lean mass hyper-responders” to explain this phenomenon. Additionally, saturated fat was found to have a substantially lesser effect on LDL cholesterol compared with carbohydrate restriction. Note that 9 of the 41 trials included in the analysis did not report saturated fat consumption, which could have been a potential limitation.6
The researchers suggest that this data is reassuring for patients considering the use of a low-calorie diet for the treatment of obesity-related disorders, although lean individuals who are adopting a low-carbohydrate diet could expect an increase in LDL cholesterol. In patients who would benefit from a low-carbohydrate diet but who experience increased LDL cholesterol, treatment with statin medications may be considered. To assess the clinical impact of isolated elevations in LDL cholesterol levels due to low-carbohydrate diets in lean individuals, more research is needed.
REFERENCES
1. Ludwig DS. The Ketogenic Diet: Evidence for Optimism but High-Quality Research Needed. J Nutr. 2020;150(6):1354-1359. doi:10.1093/jn/nxz308
2. Buren J, Ericsson M, Damasceno NRT, Sjodin A. A ketogenic low-carbohydrate high-fat diet increases LDL cholesterol in healthy, young, normal-weight women: a randomized controlled feeding trial. Nutrients. 2021;13(3):814.
3. Retterstol K, Svendsen M, Narverud I, Holven KB. Effect of low carbohydrate high fat diet on LDL cholesterol and gene expression in normal-weight, young adults: a randomized controlled study. Atherosclerosis. 2018;279:52–61.
4. Hays JH, DiSabatino A, Gorman RT, Vincent S, Stillabower ME. Effect of a high saturated fat and no-starch diet on serum lipid subfractions in patients with documented atherosclerotic cardiovascular disease. Mayo Clin Proc. 2003;78(11):1331-1336. doi:10.4065/78.11.1331
5. Dashti HM, Al-Zaid NS, Mathew TC, et al. Long term effects of ketogenic diet in obese subjects with high cholesterol level. Mol Cell Biochem. 2006;286(1-2):1-9. doi:10.1007/s11010-005-9001-x
6. Soto-Mota A, Flores-Jurado Y, Norwitz NG, et al. Increased low-density lipoprotein cholesterol on a low-carbohydrate diet in adults with normal but not high body weight: A meta-analysis. Am J Clin Nutr. 2024;119(3):740-747. doi:10.1016/j.ajcnut.2024.01.009
