Calcium, Dairy, and Body Fat in Adolescents

描述（由申请人提供）：儿童肥胖是一个日益增长的问题。我们和其他人都有证据表明，乳制品消费与体重和体脂的适度有关。这种影响是由于钙本身还是乳制品中的其他成分引起的尚不清楚。我们建议测试的假设，增加钙的摄入量，通过盐或乳制品增加粪便脂肪排泄的结果，肠皂形成，从而减少代谢能的摄入。乳制品消费也与喂养的热效应增加和脂质氧化增加有关，这将增加总能量消耗。我们假设，通过盐或乳制品增加钙的摄入量将增加总能量消耗，通过增加脂质氧化和热效应的喂养，这些影响将与血清甲状旁腺激素（PTH）和骨化三醇浓度的抑制。我们将在30名超重至中度肥胖的青春期女孩和男孩中研究这些假定的机制，他们以随机顺序，交叉设计参加两周，三周的严格控制饮食期。所有受试者将接受含650 mg钙/天的基础饮食。钙的摄入量和来源将通过每天饮用3次饮料来控制。在一段时间内，饮料不会提供额外的钙。在另一个阶段，饮料将为一半的受试者提供额外的650 mg碳酸钙/天的钙，或为另一半的受试者提供乳制品钙。将测定脂肪、能量、钙和蛋白质（氮）的平衡（摄入-排泄）。使用双标记水和静息能量消耗测定总能量消耗，并使用间接量热法测定摄食的热效应。这项研究将评估钙/乳制品作为能量平衡的调节剂，对儿童体脂管理很重要。

DESCRIPTION (provided by applicant): Childhood obesity is a growing concern. We and others have evidence that dairy consumption is associated with moderation of body weight and body fat. Whether this effect is due to calcium alone or to other constituents in dairy is unclear. We propose to test the hypothesis that increased calcium intake through salts or dairy products increases fecal fat excretion as a result of intestinal soap formation, thereby reducing metabolizable energy intake. Dairy product consumption has also been associated with an increase in thermic effect of feeding and increased lipid oxidation, which would increase total energy expenditure. We hypothesize that increased calcium intake through salts or dairy products will increase total energy expenditure by increasing lipid oxidation and thermic effect of feeding and that these effects will be associated with a suppression of serum parathyroid hormone (PTH) and calcitriol concentrations. We will study these putative mechanisms in 30 overweight to moderately obese adolescent girls and boys who participate in two, three-week strictly controlled diet periods in a randomized order, crossover design. All subjects will receive a basal diet containing 650 mg calcium/day. Calcium intake and source will be manipulated through beverages consumed 3 times daily. During one period, the beverage will provide no additional calcium. During the other period, the beverage will provide an additional 650 mg calcium/day as calcium carbonate in half of the subjects or dairy calcium in the other half of the subjects. Balance (intake-excreta) will be determined for fat, energy, calcium and protein (nitrogen). Total energy expenditure will be determined using doubly labeled water and resting energy expenditure and the thermic effect of feeding will be determined using indirect calorimetry. This study will evaluate calcium/dairy as a modulator of energy balance, important to the management of body fat in children.