Dietary advice for maintenance of weight loss: Impact of diet composition on blood lipids and cardiovascular disease risk in pre-diabetic individuals

Abstract

Background It has been established that diets high in protein (>25en%) improve weight loss and weight loss maintenance in short-term and controlled diet studies. However, the effect of these diets on cardiovascular health has not been well researched. A currently underway international Type 2 Diabetes (T2D) prevention trial offers an opportunity to look at this effect. It aims to establish the long-term (3 years) ability of an ad libitum high-protein (HP) (25en%) compared to a moderate-protein (MP) (15en%) diet to maintain weight loss and prevent T2D in pre-diabetic individuals. The primary aims of this sub-study were to determine if free-living, pre-diabetic participants consuming a HP diet also consume high amounts of saturated fat (SFA), the impact of a HP diet on maintenance of weight loss after 4 months, and the effect of these variables on cardiovascular disease (CVD) risk. Methods Data from the first 6 months of an international T2D prevention trial was utilised. Participants were eligible for this trial if aged 19-70 years, overweight (≥25kg/m2), pre-diabetic (WHO/IDF criteria) and otherwise in good health. Eligibility for this sub-study required all 4-day diet records and lipid analyses to be available. 120 male and female participnats were separated into a high (HP) (>20en% protein) or low (LP) (≤20en% protein) protein group based on their reported protein intake (en%) after an 8-week weight loss phase followed by 4 months of weight maintenance dietary advice. Serum lipid measures were analysed to show changes from baseline to 6 months. Changes to body weight, fat mass, fat-free mass, blood pressure and plasma glucose were also analysed. Results Participants lost an average of 11.8kg during the weight loss phase. Participants in both groups maintained the same body weight and fat mass loss. The consumption of protein was negatively associated with the intake of total and saturated fat. The HP group significantly decreased their triglyceride levels more than those in the LP group (p<0.01) between baseline and 6 months. No other measures of serum lipids or blood glucose significantly differed between the two diet groups. Both systolic (p<0.0001) and diastolic (p<0.01) blood pressure decreased and HDL-C increased (p<0.0001), but no difference was seen between groups. Conclusion A HP diet followed for 4 months by overweight, pre-diabetic individuals may not rely on animal-derived sources of protein and probably enables a reduction in SFA intake and TAG levels, therefore slightly improving CVD risk. However, weight loss maintenance through dietary compliance appears to be the most important factor for CVD risk reduction. HP dietary guidelines should continue to suggest consumption of predominantly vegetarian protein sources to ensure SFA intake does not increase when recommending a HP diet.