Effects of a low-carbohydrate diet on insulin-resistant dyslipoproteinemia-a randomized controlled feeding trial.

The American journal of clinical nutrition. 2022;115(1):154-162

Plain language summary

Diets high in carbohydrates and particularly processed carbohydrates can increase the risk for developing a dysfunction in the body’s ability to take up sugar from the blood, known as insulin resistance. However how this relates to insulin resistance can contribute to the development of many diseases such as type 2 diabetes, heart disease and stroke, which highlights the importance in preventing this dysfunction. This randomised control trial of 148 individuals aimed to determine the role of low, medium, and high carbohydrate diets with varying saturated fat content on measures for insulin resistance. The results showed that regardless of the fat content, it was the level of carbohydrate that determined the effect on measures of insulin resistance. High saturated fat and low-carbohydrate diets improved insulin resistance and low saturated fat high carbohydrate diets worsened insulin resistance. Improvements were also observed in blood lipids with a high fat low carbohydrate diet. It was concluded that a diet low in carbohydrates, but high in saturated fat improved insulin resistance and blood lipid levels. This study could be used by healthcare professionals to understand that a diet, which replaces fat with carbohydrates may be worsening insulin resistance and that low carbohydrate diets may be of benefit.

Abstract

BACKGROUND Carbohydrate restriction shows promise for diabetes, but concerns regarding high saturated fat content of low-carbohydrate diets limit widespread adoption. OBJECTIVES This preplanned ancillary study aimed to determine how diets varying widely in carbohydrate and saturated fat affect cardiovascular disease (CVD) risk factors during weight-loss maintenance. METHODS After 10-14% weight loss on a run-in diet, 164 participants (70% female; BMI = 32.4 ± 4.8 kg/m2) were randomly assigned to 3 weight-loss maintenance diets for 20 wk. The prepared diets contained 20% protein and differed 3-fold in carbohydrate (Carb) and saturated fat as a proportion of energy (Low-Carb: 20% carbohydrate, 21% saturated fat; Moderate-Carb: 40%, 14%; High-Carb: 60%, 7%). Fasting plasma samples were collected prerandomization and at 20 wk. Lipoprotein insulin resistance (LPIR) score was calculated from triglyceride-rich, high-density, and low-density lipoprotein particle (TRL-P, HDL-P, LDL-P) sizes and subfraction concentrations (large/very large TRL-P, large HDL-P, small LDL-P). Other outcomes included lipoprotein(a), triglycerides, HDL cholesterol, LDL cholesterol, adiponectin, and inflammatory markers. Repeated measures ANOVA was used for intention-to-treat analysis. RESULTS Retention was 90%. Mean change in LPIR (scale 0-100) differed by diet in a dose-dependent fashion: Low-Carb (-5.3; 95% CI: -9.2, -1.5), Moderate-Carb (-0.02; 95% CI: -4.1, 4.1), High-Carb (3.6; 95% CI: -0.6, 7.7), P = 0.009. Low-Carb also favorably affected lipoprotein(a) [-14.7% (95% CI: -19.5, -9.5), -2.1 (95% CI: -8.2, 4.3), and 0.2 (95% CI: -6.0, 6.8), respectively; P = 0.0005], triglycerides, HDL cholesterol, large/very large TRL-P, large HDL-P, and adiponectin. LDL cholesterol, LDL-P, and inflammatory markers did not differ by diet. CONCLUSIONS A low-carbohydrate diet, high in saturated fat, improved insulin-resistant dyslipoproteinemia and lipoprotein(a), without adverse effect on LDL cholesterol. Carbohydrate restriction might lower CVD risk independently of body weight, a possibility that warrants study in major multicentered trials powered on hard outcomes. The registry is available through ClinicialTrials.gov: https://clinicaltrials.gov/ct2/show/NCT02068885.

Lifestyle medicine

Fundamental Clinical Imbalances : Hormonal ; Immune and inflammation
Patient Centred Factors : Mediators/Insulin resistance
Environmental Inputs : Diet ; Nutrients
Personal Lifestyle Factors : Nutrition
Functional Laboratory Testing : Blood

Methodological quality

Jadad score : 3
Allocation concealment : No

Metadata

Nutrition Evidence keywords : High fat diet ; Insulin resistance