In view of the research gap in the safety of traditional ketogenic diet, there is a need for a healthy alternative to the ketogenic diet that reduces the individual's propensity to adverse diet choices. Healthy guidelines to be adopted include a diet low in saturated fat, trans fat, and sugar, along with adequate fibre. Potentially with these guidelines in effect, the associated risks for CVD would be reduced. Therefore, this study will investigate the effect of a calorie-restricted healthy ketogenic diet versus a calorie-restricted low fat diet on weight loss and metabolic outcomes among individuals with obesity.

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.

Inclusion Criteria:

• Body mass index (BMI) between 27.5 to 40 kg/m2
• Aged 21 to 65 years

Exclusion Criteria:

• Individuals with type 1 diabetes or type 2 diabetes on insulin
• heart failure
• active cancer or in remission for less than 5 years
• advanced kidney disease
• hypothyroidism
• pregnancy
• depression
• untreated anemia, known thalassaemia, or other blood disorders.

Individual participant data will remain confidential and only accessible via lock and keys by the researchers.

It is not feasible to apply blinding to the study design due to the nature of the intervention.