JCL roundtable: Low-carbohydrate diets

Extreme Hypercholesterolemia Following a Ketogenic Diet: Exaggerated Response to an Increasingly Popular Diet

A high-fat, very low-carbohydrate diet, often named the "ketogenic diet," is gaining popularity, particularly among patients with obesity and metabolic syndrome seeking rapid weight loss and improvement in glycemic control. A favorable reduction in triglycerides and an increase in high-density lipoprotein-cholesterol levels is often observed in the ketogenic diet. However, people vary significantly in their low-density lipoprotein-cholesterol (LDL-C) response to the dietary change. Here, we present the case of a 38-year-old normal-weight male with average cholesterol levels showing an extreme fourfold elevation in LDL-C levels, reaching 496 mg/dL after initiating a ketogenic diet. We highlight that a dramatic elevation in LDL-C may manifest following a ketogenic diet in normal-weight people without known genetic dyslipidemias before the dietary change; therefore, increased awareness and close monitoring of blood lipid profile is essential for all individuals following a ketogenic diet. We further discuss the potential mechanisms for the "lean mass hyper-responders" phenotype which has been recently gaining recognition, and suggest that these patients may benefit from ezetimibe therapy, decreasing the absorption of intestinal cholesterol to the liver.

Gut Microbiota Serves a Predictable Outcome of Short-Term Low-Carbohydrate Diet (LCD) Intervention for Patients with Obesity

To date, much progress has been made in dietary therapy for obese patients. A low-carbohydrate diet (LCD) has reached a revival in its clinical use during the past decade with undefined mechanisms and debatable efficacy. The gut microbiota has been suggested to promote energy harvesting. Here, we propose that the gut microbiota contributes to the inconsistent outcome under an LCD. To test this hypothesis, patients with obesity or patients who were overweight were randomly assigned to a normal diet (ND) or an LCD group with ad libitum energy intake for 12 weeks. Using matched sampling, the microbiome profile at baseline and end stage was examined. The relative abundance of butyrate-producing bacteria, including Porphyromonadaceae Parabacteroides and Ruminococcaceae Oscillospira, was markedly increased after LCD intervention for 12 weeks. Moreover, within the LCD group, participants with a higher relative abundance of Bacteroidaceae Bacteroides at baseline exhibited a better response to LCD intervention and achieved greater weight loss outcomes. Nevertheless, the adoption of an artificial neural network (ANN)-based prediction model greatly surpasses a general linear model in predicting weight loss outcomes after LCD intervention. Therefore, the gut microbiota served as a positive outcome predictor and has the potential to predict weight loss outcomes after short-term LCD intervention. Gut microbiota may help to guide the clinical application of short-term LCD intervention to develop effective weight loss strategies. (This study has been registered at the China Clinical Trial Registry under approval no. ChiCTR1800015156). IMPORTANCE Obesity and its related complications pose a serious threat to human health. Short-term low-carbohydrate diet (LCD) intervention without calorie restriction has a significant weight loss effect for overweight/obese people. Furthermore, the relative abundance of Bacteroidaceae Bacteroides is a positive outcome predictor of individual weight loss after short-term LCD intervention. Moreover, leveraging on these distinct gut microbial structures at baseline, we have established a prediction model based on the artificial neural network (ANN) algorithm that could be used to estimate weight loss potential before each clinical trial (with Chinese patent number 2021104655623). This will help to guide the clinical application of short-term LCD intervention to improve weight loss strategies.