The influence of dietary modifications and weight loss on plasma lipids and lipoproteins

• Main Author: Harman, Nicola Louise
• Published: University of Surrey 2007
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731109

The studies presented in this thesis investigated dietary strategies to reduce cardiovascular (CV) risk associated with atherogenic dyslipidaemia. The thesis also describes the development of a new method for the separation of the principal HDL subclasses. The 'RISCK' study five examined the effects of five diets, differing in the type and amount of dietary fat and carbohydrate, on plasma lipids in subjects at risk of developing metabolic syndrome. All diets showed a significant reduction in serum total, and LDL cholesterol. Whilst no diet was superior in its lipid-lowering effect, the two low fat diets reduced waist circumference and other CV risk factors, suggesting a link between a reduction in visceral adiposity and CV risk The 'EDWINA' study addressed the effects of energy restriction and increased dietary cholesterol in the form of eggs, on body weight and plasma lipids. Energy restriction and energy restriction +2 eggs/day for 12 weeks achieved significant weight loss (3- 4kg). Increased egg consumption had no significant effect on plasma LDL cholesterol, suggesting that weight loss negates the cholesterol raising potential of dietary cholesterol. The weight loss and lipid response in the 'EDWINA' study was highly variable between subjects. Apo E genotype and serum non-cholesterol sterols (markers of cholesterol homeostasis) were measured to investigate the origin of this variability. Carriage of the epsilon4 allele was significantly associated with higher serum sitosterol (marker of cholesterol absorption) at baseline, however, apoE genotype did not explain the heterogeneity in response to diet. There was some indication from reductions in serum lathosterol, that falls in plasma cholesterol were associated with reduced cholesterol biosynthesis. The overall findings provide further evidence to support the CV health benefits of losing weight and especially visceral adiposity. They also highlighted the importance of dietary composition of energy restricted diets in modifying lipid mediated CV risk.