Blood Lipid Responses to Diet Macronutrients

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Dietary and lifestyle interventions are central to lowering the risk and preventing the development of metabolic disease, including non-alcoholic fatty liver disease, type 2 diabetes, and cardiovascular disease. There is, however, no one fits all dietary approach, and in the context of diets where an individual is not gaining or losing weight (known as eucaloric), the optimal macronutrient composition associated with a reduced risk of metabolic disease and dyslipidemia is highly debated. For instance, eating less of one macronutrient implies eating more of another; a reduction in the intake of dietary carbohydrates is met by an increase in dietary fats. How this affects one's metabolic health in the setting when someone is not gaining or losing body weight is unclear. Therefore, this study aims to provide an understanding of the effect that the quantity of specific dietary macronutrients (e.g., carbohydrates, fats) have on plasma triglyceride concentrations in both the fasting and postprandial state, liver fat content and metabolism, and cardiac fat content and function. An individual's genotype affects the metabolic response to a shift in dietary macronutrient content and this will be examined in this study. Sixty volunteers free from metabolic disease will be recruited into a randomized, parallel-armed dietary intervention study. Participants will consume either a low carbohydrate, high-fat diet or a high carbohydrate, low-fat diet for up to 28 days. Diets will be eucaloric (i.e., designed to meet the individual participant's energy requirements). Comprehensive in vivo metabolic and physiological testing will be performed before and after the experimental diet to document the effects of the overconsumption of specific macronutrients (i.e., fats or carbohydrates) on liver and lipid metabolism.