Obesity is one of the mot significant international health problems. In spite of the importance of eating behaviors in causing and maintaining obesity, eating patterns are not well understood. The role in psychological precipitants of eating behavior is particularly unclear and has critical implications to understanding the etiology, maintenance, and, especially, treatment of obesity. Previous studies that have assessed eating patterns and their precipitants have relied on retrospective recall of past behaviors or diary methods, both of which are strongly influenced by cognitive biases and may have resulted in data of poor quality.
This study proposes to investigate psychological precipitants of eating behavior in obesity using a state-of-the-art measurement technique called Ecological Momentary Assessment (EMA). EMA consists of longitudinal daily sampling that allows for the evaluation of psychological variables in "real time," resulting in more accurate observations and minimizing cognitive biases in self-report and recall. Although previous studies have evaluated psychological precipitants of dieting and binge eating behavior, psychological antecedents of more typical eating patterns among the obese have not been assessed using EMA.
This investigation will identify specific psychological precipitants associated with food consumption, including mood, the subjective experience of loss of control, and cognitions about the hedonic value of food and the importance of weight loss. Identifying psychological variables that precipitate eating behavior will facilitate more effective weight loss and weight maintenance treatments as well as the development of more accurate etiological models of obesity.
William B. Schrage, Ph.D.
Mayo Clinic, Rochester, MN
The objective of our research proposal is to gain insight into fundamental vascular control mechanisms in obese humans. Very little is known regarding the hemodynamic response to exercise, or the mechanisms controlling blood flow during exercise in obese humans. Obese humans exhibit endothelial dysfunction and reduced exercise capacity. Animal studies suggest obesity is associated with reduced nitric oxide (NO) mediated vasodilation, enhanced prostaglandin (PG) mediated vasoconstriction, and reduced exercise blood flow. In non-obese adults, inhibition of NO or PGs reduces blood flow in the exercising forearm, suggesting both signals contribute to increasing muscle blood flow.
The aim of this study is to determine whether alterations in NO and PGs contribute to reduced skeletal muscle blood flow in obese humans, and whether obesity alters the structure, function, and protein expression in muscle microcirculation. We hypothesize inhibition of NO or PGs in lean healthy adults will reduce leg muscle blood flow during exercise. In obese humans, we hypothesize muscle blood flow will be lower than lean adults, and that NO inhibition will not reduce blood flow, but PG inhibition will actually increase blood flow. We will also test this hypothesis in vitro with isolated human skeletal muscle resistance arteries obtained from muscle biopsies. We hypothesize that resistance arteries from obese humans will exhibit altered mRNA and protein expression that result in less NO and PG mediated vasodilation and more PG mediated vasoconstriction along with greater oxidative stress.
Results from this study will provide fundamental information toward understanding mechanistic control of muscle blood flow in lean and obese humans. Moreover, we will be the first laboratory to obtain molecular and biochemical insight into how obesity might alter control of blood flow in human muscle microcirculation.
The purpose of the proposed study is to evaluate the effects of eating breakfast and to examine the content of breakfast meals on appetite, mood, and cognitive performance in boys. Eating a nutritious breakfast is an important part of a healthy lifestyle, especially in youth. However, many studies have documented high rates of skipping breakfast among youth. While the literature includes many cross-sectional studies demonstrating inverse associations between breakfast frequency and body weight, prospective and experimental studies are lacking. The few studies that have measured effects of breakfast habits on mood or cognitive skills, while provocative, suffer from a variety of limitations. We hypothesize that children will be less hungry, less irritable, more energetic, and demonstrate superior memory and analytical skills following a breakfast meal in comparison to skipping breakfast.
Due to effects of dietary composition on blood glucose and satiety, we further hypothesize that children may be less hungry and perform better on these parameters following a balanced breakfast meal containing whole grain, fruit, and milk than after a refined carbohydrate breakfast meal including a pastry and fruit juice. The proposed study will include a cross-over experimental design in boys and girls from summer day camps, in good health and between the ages of 10 and 13. The participants will come to the day camps on three separate mornings following an overnight fast. The three test days will be separated by a period of at least two days and will occur on weekdays over the summer months.
In random order, the three different test meals fed during the morning will be:
balanced breakfast, and
refined carbohydrate breakfast.
Over several hours following the meal we will be assess perceived hunger, mood, energy levels, physical activity, memory and analytical skills. The outcomes will be compared over the three conditions using repeated measures regression analysis. The study findings may provide insight into the role of breakfast habits in modulating energy regulation, behavior, and academic performance, and therefore lay important groundwork to be further developed in larger and longer studies.
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