Almost 50 years ago, Donald Zilversmit proposed that the physiologic response to a high-fat meal revealed key dynamics related to the development of heart disease.  This area of research has been widely expanded and includes the concept of metabolic flexibility (an efficient switch to whole-body carbohydrate oxidation after consuming sugars) and the concept of nutrient toxicity during overconsumption of energy.  Within highly heterogeneous populations (people of different sexes, race/ethnicities, ages, and fitness levels) the responses exhibited after a nutrient challenge are highly variable, while the responses to fasting is highly predictable and similar between people.  Thus, measuring physiologic responses to the act of eating uncovers disease risks less apparent in fasting blood samples.  A number of study design features will impact the response to a meal, and therefore influence interpretation of results.  These include the composition and energy content of the test meal, food intake the day before the meal test, and recent physical activity.  This presentation will review important aspects of research rigor to study post-meal events such as subject preparation and sampling protocols for measuring metabolites.  Minimizing the impact of non-food factors that increase subject variability has been the goal of recent postprandial studies.  On the other hand, if the purpose of the research is to assess the natural variability in response to eating via assessment of the physiologic pattern encompassing all factors influencing real-life responses, then one may intentionally choose to not control any of the factors listed above.  Given that fed-state events contribute significantly to chronic disease risk, improved methods to study the absorption and disposal of energy will support the development of individualized prevention and treatment strategies to counteract diseases associated with the chronic over-consumption of food.