The observation that events occurring after consumption of a meal can directly affect metabolic risk has been gaining interest over the past 40 years. As a result, the desire for investigators to conduct postprandial studies has also increased. Study design decisions pertaining to the choice of meal quantity and composition are more difficult than may be readily apparent, and there is now ample evidence available in the literature to suggest that what is fed on the test day significantly affects postprandial metabolism and can therefore influence interpretation of results. In addition, events occurring before the testing day (food intake and activities) can also have an impact on the observed postprandial response. The goal of this review is to present aspects of study design critical to the investigation of postprandial metabolism. These details include subject preparation, meal quantity, form and composition, as well as sampling protocols for measuring metabolites. Key factors and practical examples are provided to minimize the impact of nonresearch variables on subject variability. Finally, aspects related to using stable isotope tracers to measure metabolism of meal fat are discussed, including choice of tracer form, dose and delivery in food. Given that fed-state events contribute significantly to chronic disease risk, improved methods to study the absorption and disposal of food energy will support the development of strategies designed to prevent and treat diseases associated with overconsumption of nutrients.International Journal of Obesity Supplements (2012) 2, S43 --S50; doi:10.1038/ijosup.2012.22Keywords: dietary fat; stable isotope; postprandial lipids; meals; fatty acids
INTRODUCTIONThe atherogenicity of the postprandial state, first proposed by Donald Zilversmit, 1 has remained the focus of intense research for over 4 decades. A central idea evolving from Dr Zilversmit's hypothesis is that the physiologic response to a meal high in fat reveals key dynamics related to prediction of heart disease risk. 2 The concept of a nutrient challenge as a vehicle to uncover disease risk has grown to include studies of metabolic flexibility 3 and the role of nutrient toxicity during overconsumption of food. 4 Over the past 20 years, advanced techniques for the study of postprandial lipemia have been developed. 5--9 Reviews on postprandial triacylglycerols (TG) response have described the influence of genetic polymorphisms, 2 the impact of subject characteristics such as obesity 10 and the effect of commonly prescribed medications. 11 Further, recent research has made major progress in our understanding of the metabolic fates of dietary fatty acids in humans 12 and the large variability exhibited between study subjects with respect to fatty acid handling. 13 At the same time, much new information has become available with which to optimize postprandial study designs, and the objective of this review is to highlight that information.It may seem that the impact of detailed study design features, such as feeding liq...