44-year-old man • elevated total cholesterol • chest pains • ketogenic diet • Dx?

DISCUSSION

Low-carbohydrate (low-carb) and ketogenic diets have grown in popularity throughout the United States over the past decade, particularly for weight loss, and the diet has entered the popular consciousness with several celebrities publicly supporting it.¹ Simultaneously, there also has been a growing interest in these diets for the treatment of chronic diseases, such as type 2 diabetes.² However, the long-term cardiovascular effects of low-carb diets are not well studied, and there is significant heterogeneity among these diets.

Low-carb vs low-fat. Multiple meta-analyses comparing low-carb diets to low-fat diets have found that those following low-carb diets have significantly higher total cholesterol and LDL levels.^3,4,5 The National Lipid Association’s review of evidence determined that LDL and total cholesterol responses vary in individuals following a low-carb diet, but that increasing LDL levels in particular were concerning enough to warrant lipid monitoring of patients on low-carb diets.⁶ Another meta-analysis evaluated the difference in estimated atherosclerotic cardiovascular disease (ASCVD) risk between low-carb and low-fat diets, finding those following a low-carb diet to have a lower estimated ASCVD risk but higher LDL levels.⁷

The severe worsening of this patient’s LDL levels was likely related to his ketogenic diet and was a factor in the early onset of CAD.

Weighing the benefits and harms. Since our patient’s dramatic weight loss and greatly increased exercise level would be expected to lower his LDL levels, the severe worsening of his LDL levels was likely related to his ketogenic diet and was a factor in the early onset of CAD. The benefits of low-carb diets for weight loss, contrasted with the consistent worsening of LDL levels, has prompted a debate about which parameters should be considered in estimating the long-term risk of these diets for patients. Diamond et al⁸ posit that these diets have beneficial effects on “the most reliable [cardiovascular disease] risk factors,” but long-term, patient-oriented outcome data are lacking, and these diets may not be appropriate for certain patients, as our case demonstrates.

A reasonable strategy for patients contemplating a low-carb diet specifically for weight loss would be to use such a diet for 3 to 6 months to achieve initial and rapid results, then continue with a heart-healthy diet and increased exercise levels to maintain weight loss and reduce long-term cardiovascular risk.

Our patient was started on a post­operative medication regimen of aspirin 81 mg/d, evolocumab 140 mg every 14 days, metoprolol tartrate 25 mg bid, and rosuva­statin 10 mg/d. A year later, he was able to resume a high level of physical activity (6-mile runs) without chest pain. His follow-up lipid panel showed a total cholesterol of 153 mg/dL; LDL, 53 mg/dL; HDL, 89 mg/dL; and triglycerides, 55 mg/dL. He had also switched to a regular diet and had been able to maintain his weight loss.

THE TAKEAWAY

Growing evidence suggests that low-carb diets may have a significant and detrimental effect on LDL levels. The long-term safety of these diets hasn’t been well studied, particularly regarding cardiovascular outcomes. At a minimum, patients who initiate low-carb diets should be counseled on general dietary recommendations regarding saturated fat and cholesterol intake, and they should have a follow-up lipid screening to evaluate for any significant worsening in total cholesterol and LDL levels.

CORRESPONDENCE
Samuel Dickmann, MD, 13611 NW 1st Lane, Suite 200, Newberry, FL 32669; sbcdickmann@ufl.edu