The effects of a low-carbohydrate, high-fat diet on type 2 diabetic patients

Thesis submitted to the Department of Human Movement Science in fulfilment of the requirements for the award of Philosophiae Doctor in Human Movement Science, Faculty of Science and Agriculture at the University of Zululand, 2019.

Diabetes amongst South Africans is increasing at an alarming rate. With 8.27% – 9% of the population suffering from diabetes, the majority is Type 2. It is predicted that diabetes will have doubled by 2030. The aims of this study were first to determine the effectiveness of a low carbohydrate high fat diet (LCHFD) on Type 2 diabetic patients. Secondly, to see what the effects of a concurrent physical activity programme with an LCHFD will have on Type 2 diabetic patients. Lastly, this study aimed to determine the effects on cholesterol and lipoproteins using an LCHFD on Type 2 diabetic patients. Participants were recruited from patients registered at the Richards Bay Diabetic Clinic and surrounding area in Zululand, KwaZulu-Natal, South Africa and were screened and received approval by a medical doctor at the diabetic clinic for participation in the study. Twenty-eight female and eleven male Type 2 diabetics (N = 39) aged 31-71 years were assigned into either a concurrent physical activity and LCHFD group (DiExG) (n = 14) which followed a 16-week program consisting of physical activity program entailing walking a minimum of 10 000 steps daily (measured using a pedometer wristband) combined with an LCHFD requiring participants not to consume more than 50grams (g) of carbohydrates per day for the 16-week experimental period, LCHFD only group (DietG) (n = 11) which were required to follow an LCHFD requiring participants not to consume more than 50g of carbohydrates per day or control group (ConG) (n = 14), whose members continued with their normal daily activities throughout the 16-week period. Of the initial 39 patients with Type 2 diabetes mellitus who were eligible to participate in the study, 35 patients (DiExG: n=12, DietG: n=10, ConG: n=13) completed the study and were included in the final analysis. The results revealed no significant (p>0.05) changes in glycated haemoglobin (HbA1c), glucose and insulin in either the DiExG (HbA1c: p=0.592; 8.3% decrease, glucose: p=0.477; 11.1% decrease and insulin: p=0.367; 44.1% increase) or DietG (HbA1c: p=0.822; 0% change, glucose: p=0.108; 11.0% decrease and insulin: p=0.976; 4.2% decrease). No significant (p>0.05) changes were found in the DiExG and DietG regarding body mass (p=0.999; 2.0% decrease and p=0.991; 2.5% decrease; respectively), body mass index (BMI) (p=0.999; 2.2% decrease and p=0.998; 2.3% decrease; respectively), percentage body fat (%BF) (p=0.693; 16.7% decrease and p=0.928; 13.0% decrease, respectively), waist circumferences (p=0.929; 5.4% decrease and p=0.71; 6.3% decrease, respectively), hip circumference (p=0.85; 5.8% decrease and p=0.414; 7.0% decrease; respectively) and waist-to-hip ratio (WHR) (p=0.999; 0% difference and p=0.999; 0% difference, respectively). No significant (p>0.05) changes were observed in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) in either the DiExG (TC: p=0.791; 2.0% increase, LDL-C: p=0.704; 7.4% increase, TG: p=0.477; 9.5% decrease and HDL-C: p=0.989; 0% change) or DietG (TC: p=0.881; 0% change, LDL-C: p=0.744; 13.8% decrease, TG: p=0.677; 17.9% increase and HDL-C: p=0.844; 0% change). In conclusion, neither an LCHFD alone or in combined with a physical activity programme failed to elicit improvements in insulin sensitivity and should not indisputably be included in a treatment regime to manage or improve body composition in Type 2 diabetics. As such, adoption of an LCHFD, either alone or combination with physical activity, should not unequivocally be adopted as part of the treatment approach for Type 2 diabetics and should carefully be weighed against the benefits of more traditional dietary and/or physical activity interventions. This study further concludes that the LCHFD with or without exercise has no beneficial or negative adaptations to cholesterol in Type 2 diabetics.