Obesity represents one of our nation's leading public health issues. In 2017, over 30% of U.S. high school students had either overweight (15.6%) or obesity (14.8%), and the average U.S. BMI continues to rise. Overall, this increasing trend is associated with earlier mortality and lower quality of life. In 2005 it was projected that if current U.S. weight trends continued, the average lifespan would decrease by about 9 months. Documented declines exceed this calculation, with rises in BMI relating to an estimated 11-month decrease in life expectancy in 2011. In adolescents specifically, this epidemic shares associations with many negative health outcomes including poorer sleep quality, impaired academic performance, and lower cognitive function. Thus, it is imperative that researchers work to understand the complex nature of this preventable disease and recognize its significant longitudinal health implications.
One factor significantly related to overweight/obesity (OWOB) is decreased cognitive function. However, the causal nature of this relationship is unclear. It has been hypothesized that impaired cognitive function and poor inhibition could predict increased food consumption, thus contributing to the association between cognitive deficits and OWOB. Alternatively, it has been suggested that biological factors stemming from obesity (i.e. low grade inflammation, insulin resistance, low blood flow, and increased levels of cytokines and leptin) work to exacerbate preexisting cognitive impairments, or are perhaps fully responsible for the cognitive deficits seen in individuals with OWOB. Thus, further research is needed to clarify these relationships.
Research regarding OWOB and cognitive function has left a critical gap in the literature by failing to consider the role of sleep within this relationship. Current evidence shows that more than 2/3 of adolescents fail to attain the recommended minimum of 8 hours of sleep during the week. However, a meta-analysis found that every added hour of sleep that adolescents do secure relates to a 9.0% decrease in obesity risk. In line with this finding, sleep restriction is associated with increased appetite, hunger, and poorer nutritional food choices. Sleep restriction has also been tied to impairments in cognitive function including decreased working memory and attention. Thus, it is possible that the relationship between OWOB and cognitive function in adolescents is influenced by sleep behaviors.
Another important factor to consider in the relationship between OWOB and cognitive function is stigma. Weight stigma is a pervasive problem with multiple implications for physical health. For example, chronic low-grade inflammation represents a known correlate of chronic stress and stigmatization. This is significant as elevated inflammation also relates to OWOB and decreased cognitive function. Thus, the experience of weight related stigma may exacerbate existing inflammation in individuals with OWOB, further impairing cognitive function.
The present study seeks to expand our knowledge of these complex relationships, exploring the associations between weight status, eating behavior, cognitive function, sleep, and stigma. To do this, the study will utilize data from 2 groups: adolescents with normal weight and adolescents with OWOB. Adolescents in each group will complete two sleep conditions in a randomized order: adequate and restricted. Each sleep condition will be followed by a self-serve breakfast and completion of a cognitive battery. Prior to completing the sleep conditions, adolescents will participate in a baseline appointment during which they will complete a questionnaire regarding weight related stigma experiences.
The investigators propose that cognitive function and sleep restriction may relate to adolescent weight status through the following mechanisms: 1) elevated adiposity will predict greater impairments in cognitive functioning, poorer nutritional intake, and greater food consumption, 2) sleep restriction will result in impaired cognitive functioning, poorer nutritional intake, and increased food consumption in all adolescents, 3) sleep restriction in adolescents with elevated adiposity will result in the greatest cognitive impairments, poorest nutritional intake, and greatest food consumption, and 4) decreased cognitive function will be associated with poorer nutritional intake and greater food consumption in all adolescents. The investigators also propose that stigma experiences relate to adolescent weight status through the following mechanisms: 1) heightened stigma experiences will predict impairments in cognitive functioning in all adolescents and 2) elevated adiposity will relate to greater stigma experiences and subsequently higher cognitive impairments, resulting in the worst outcomes for assessments of cognitive function .
