A new study reveals that while low-carb, high-fat diets may spare saturated fats and carbs from blame, high cholesterol and salt intake still threaten heart health—urging smarter food choices even in trendy diets.

Study: Low carbohydrate high fat-diet in real life; A descriptive analysis of cardiovascular risk factors. Image Credit: 19 STUDIO / Shutterstock

In a recent study published in the International Journal of Cardiology, Cardiovascular Risk, and Prevention, researchers investigated dietary variations in a real-world low-carbohydrate high-fat (LCHF) population and its relationship with cardiovascular risk factors.

LCHF diets are popular for blood glucose control and weight loss; however, personal beliefs and reasons may influence dietary choices. The primary feature of LCHF diets is the decrease in dietary carbohydrates, which are mainly replaced with fats. Dietary recommendations tailored for patients preferring LCHF diets are non-existent. LCHF diets commonly include natural, unprocessed foods.

Saturated fat-rich foods are preferred over low-fat alternatives. Nevertheless, saturated fats and cholesterol are associated with higher risks of cardiovascular disease, while unsaturated fats offer benefits. Several trials have shown substantial increases in low-density lipoprotein (LDL) cholesterol levels among healthy individuals following a low-carbohydrate, high-fat (LCHF) diet.

About the study

The present study investigated dietary variations in a real-world low-carbohydrate, high-fat (LCHF) population and their associations with cardiovascular risk factors. The team recruited volunteers who reported adherence to an LCHF diet for at least three months. Subjects did not use lipid-lowering medications and were free from familial hyperlipidemia. Participants’ weight, height, hip and waist circumference, and blood pressure (BP) were measured. Further, urine and blood samples were collected.

Participants’ activity was monitored for a week to estimate total energy expenditure (TEE). Dietary recall interviews were conducted to assess the nutritional composition of the diet. Energy intake (EI) was compared with TEE. Subjects with plausible EI levels were deemed acceptable reporters. Subjects also reported whether they were weight stable. Further, basal metabolic rate, physical activity level (PAL), and food intake level (FIL) were calculated.

The Shapiro-Wilk’s test assessed normal distributions, and stepwise linear regression modeling was performed. Outcome variables included glycated hemoglobin (HbA1c), systolic blood pressure (SBP), lipid profile, and diastolic blood pressure (DBP). Explanatory variables were age, sex, PAL, FIL, EI, body mass index (BMI), sodium intake, cholesterol intake, alcohol intake, saturated fatty acids (SFAs), and proportion of energy (E%) from protein, fat, and carbohydrates.

The step model was bidirectional, starting as an intercept-only model, and predictive variables were sequentially added. The next best-fitting predictive variable was identified based on the Akaike information criterion. The primary statistical analyses included only acceptable reporters. In sensitivity analyses, all participants, including those reporting weight stability, were included.

Findings

Overall, 100 volunteers participated in this study. Nearly two-thirds were female, none were smokers, and 83 were acceptable reporters. Participants’ median age and BMI were 48.7 years and 25.7 kg/m², respectively. The median SBP, HbA1c, total cholesterol (TC), LDL cholesterol, and high-density lipoprotein (HDL) cholesterol were 120 mmHg, 35 mmol/mol, 6.2 mmol/L, 3.8 mmol/L, and 1.8 mmol/L, respectively.

The median carbohydrate intake was low (8.7 E%) and compensated with a higher EI from fats (72.3 E%). Likewise, dietary fiber intake was low at 13 g/day. Advanced age was associated with an increased LDL, TC, BP, HbA1c, and HDL. Further, male sex was associated with higher HbA1c, triglycerides, and lower HDL, whereas increased BMI was associated with reduced TC and HDL and elevated DBP and triglycerides (contradicting trends observed in the general population).

Furthermore, dietary cholesterol was associated with higher TC, HDL, and LDL. Protein intake was associated with lower HDL and DBP (aligning with known blood pressure-lowering effects but contrasting typical protein-HDL associations), whereas fiber intake was associated with a slightly higher HbA1c (though the paper notes this might be a chance finding) and lower TC and LDL. Alcohol intake was associated with higher triglycerides and lower HbA1c. There were no associations of SFA or carbohydrate intake with any outcome variable.

EI and energy expenditure were not associated with meaningful changes in any outcome. In analyses involving all subjects, there was an association between male sex and higher SBP and between protein intake and lower SBP. These associations were not observed when individuals reporting weight stability were included.

Conclusions

In sum, carbohydrate intake was low in this real-world LCHF population, and minor variations were not associated with cardiovascular risk factors. Cholesterol intake was high and associated with poor lipid profiles, while sodium intake was associated with higher BP. These findings have also substantiated the concerns of low fiber intake in LCHF diets.

Low fiber intake was associated with a poor lipid profile. Because the study was cross-sectional, the findings may not be conclusive, and longitudinal studies are needed to further explore the associations. Overall, these results reinforce the dietary recommendations to include fiber-rich foods in LCHF diets while avoiding excessive cholesterol and salt intake.