The Effect of a Healthy Ketogenic Diet Versus Calorie-restricted Low Fat Diet on Weight Loss and Metabolic Outcomes for Obesity: A Randomised Controlled Trial

The ketogenic diet has recently gained popularity as an effective dietary plan for weight management. Some of the cited benefits include a reduction in appetite and hunger, as well as improvements in fat oxidation leading to weight loss. Remarkably, some studies have also demonstrated increases in high-density lipoprotein (HDL) cholesterol and decreases in triglyceride levels, which point to a reduction in cardiovascular disease (CVD) risk.

In spite of these, there are still widespread concerns regarding the potentially high proportion of total and saturated fats derived from ketogenic diets owing to the high-fat and moderate-protein nature. These are associated with elevated low-density lipoprotein (LDL) cholesterol levels which may offset the purportedly lower CVD risk, especially in obese individuals. Furthermore, few randomised controlled trials (RCTs) have placed emphasis on the reduction of saturated fat, leading to confounding effects on the safety of the traditional ketogenic diet. To address the research gap, our study aims to assess the effect of a calorie-restricted healthy ketogenic diet, as compared to a calorie-restricted low fat diet on weight loss and metabolic outcomes among Asian individuals with obesity.

In this randomized controlled trial, participants will be randomly assigned to either the healthy ketogenic diet (HKD) or low fat calorie-restricted diet (LFD) using computer-generated random sequencing. Both the HKD and LFD groups will attend group workshops conducted by dietitians at weeks 1, 3, 5, 7, and thereafter at 6-week intervals over the course of a 6-month period.

The participants will be recommended to achieve their incremental daily step count goal from 3,000, 7,000 to 10,000 to promote increased physical activity, as per their tolerance. All participants are to provide for their own meals and follow a calorie-restricted diet with emphasis on the consumption of healthy fats and the reduction of saturated and trans fats in both diets.

Participants in the HKD group will be advised to follow a calorie-restricted healthy ketogenic diet (n=35), with a maximum of 50g net carbohydrate intake daily. Those in the control group will be instructed to follow a calorie-restricted low fat diet (LFD) (n=35). Calorie prescriptions for both diets were calculated based on the Schofield equation, adjusted with a deficit of 500 kcal daily to promote weight loss. Participants will also be recommended to use the Nutritionist Buddy (nBuddy) mobile application to facilitate monitoring of diet intake, steps count and to aid in their adherence to the diet and physical activity recommendations.