Environmental Influences on Intake and Obesity

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The aim of the proposed studies is to develop nutritionally sound dietary strategies that reduce energy intake in order to promote weight loss and prevent obesity. Previous research indicates that a promising approach is to systematically vary properties of foods such as energy density (calories per gram), portion size, and variety in order to moderate energy intake. Dietary strategies based on variations in these food properties will be developed that encourage increased intake of foods low in energy density, such as vegetables, during a meal. Increased consumption of low-energy-dense foods has been shown to enhance satiety and reduce energy intake, and has been used successfully to promote weight loss. Four studies using a randomized design will be conducted in men and women, who on a number of separate days will eat all of their meals in a controlled laboratory setting. The primary experimental outcomes will be energy intake and food consumption patterns at a series of test meals consisting of meat, grain, and vegetables served simultaneously, in which the low-energy-dense component (vegetables) is varied systematically. The specific aims are to determine the following: 1) the effect of increasing the portion size of vegetables either by adding extra vegetables or by substituting vegetables for other foods at a meal; 2) the effect of varying the energy density of the vegetables; 3) the effect of combining vegetables with other foods at a meal compared to serving them separately; and 4) the impact of increasing the variety of vegetables. The effectiveness of these meal manipulations in controlling hunger and maintaining satiety while promoting reduced energy intake will be assessed. In all studies, the role of individual characteristics (such as weight status, dietary restraint, and food preferences) in determining responsiveness to meal manipulations will be investigated. With the widespread availability of a variety of large portions of energy-dense foods, along with the likelihood that much of the population is susceptible to such food cues, there is an urgent need to find effective strategies that will help consumers moderate their energy intake. The proposed studies will systematically vary the energy density, portion size, and variety of vegetables to determine how these properties of foods can be used to increase intake of low-energy-dense foods and reduce energy intake in a meal. A better understanding of these effects and how they differ among individuals will facilitate the development of specific meal-related strategies and public health messages to help moderate energy intake and improve diet quality during weight management.