Temporal Dietary and Physical Activity Patterns are Associated with Obesity
Obesity is a major public health problem globally and in the United States (U.S.). Amongst adults in the U.S., prevalence estimates of obesity reached 42.4% in 2017-2018 . Obesity is both a contributor and outcome of chronic disease development including type 2 diabetes and metabolic syndrome [2,3]. Underlying modifiable risk factors for these chronic conditions include lifestyle habits such as dietary intake and physical activity.
Much of nutrition research investigating the relationship of dietary intake to health outcomes has taken a reductionist approach with a focus on single nutrients and food groups; however, the complexity of the overall diet with all its constituents is being increasingly recognized. Dietary patterns examine the quantities, frequencies, and combinations of food and beverages consumed allowing a more comprehensive investigation of the diet-health relationship , yet, the concept and creation of patterns have not considered elements beyond nutrients and food, such as time of eating, which could be an important aspect of dietary patterns. Moreover, most physical activity research has focused on the effect of intensity or counts of activity on health [5–8], while studies investigating daily physical activity patterns have focused on distinct time periods i.e., type of day (weekday vs. weekend) or seasonality [9,10]. Nevertheless, connecting these patterns to health outcomes through the integration of time across an entire day has received little attention.
Studies that have incorporated time to the concept of dietary patterns focus on behaviors such as breakfast skipping and late meal consumption and show associations with health [11–14]. For instance, compared to early lunch eaters, late lunch eaters lost less weight and had reduced glucose tolerance [15,16]. In contrast, studies that have investigated timing of exercise focused on early vs. evening exercise [17–19]. For example, exercise performed in the morning vs. evening has been associated with a greater reduction in weight and odds of obesity [17,18]. Furthermore, several studies have investigated links between timing of exercise relative to a single meal or over a single day with health [20–24] and revealed a potential benefit to modulating time of these behaviors on postprandial metabolic response. Together, these studies establish the importance of timing of these behaviors in terms of links to health; however, studies are limited by a focus on single time spans or blocks of time in a day. Consideration of the patterns of dietary intake and activity throughout a day, or “temporal dietary and physical activity patterns”, are a novel concept that may provide insight to the behavioral patterns related to health outcomes. Notably, one of the challenges in this work is utilizing methods that will characterize dietary and physical activity patterns as an exposure by integrating timing and other characteristics of these patterns in relation to health.To our knowledge, there are no published reviews that have emphasized joint consideration of the time of eating and exercise, with a focus on the time of day of these events and association with health outcomes. Therefore, Chapter 1 focuses on summarizing current literature that has integrated both of these concepts by answering the question, how does the timing of exercise relative to eating throughout the day effect postprandial response in adults? Moreover, Chapters 2 and 3, include primary research in which a novel distance measure, based on dynamic time warping, is used to develop independent temporal dietary and physical activity patterns over a 24-hour period using data from the National Health and Nutrition Examination Survey and examine their association with short- and long-term health outcomes.