Calcium, Dairy, and Body Fat in Adolescents

描述(申请人提供)：儿童肥胖是一个日益令人担忧的问题。我们和其他人有证据表明，乳制品消费与体重和体脂的适度有关。目前尚不清楚这种影响是由钙本身还是乳制品中的其他成分造成的。我们建议检验这一假设，即通过盐类或乳制品增加钙摄入量会增加肠道肥皂形成导致的粪便脂肪排泄，从而减少代谢能量的摄入量。乳制品的消费还与喂养的热效应增加和脂肪氧化增加有关，这将增加总的能量消耗。我们假设，通过盐或乳制品增加钙摄入量将通过增加脂肪氧化和喂养的热效应来增加总能量消耗，这些影响将与抑制血清甲状旁腺激素(PTH)和骨化三醇浓度有关。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，这些女孩和男孩参与了两个、三个星期的严格控制饮食时期，采用随机顺序交叉设计。所有受试者将接受每天650毫克钙的基础饮食。钙的摄入量和来源将通过每天饮用3次的饮料来控制。在一段时间内，该饮料不会提供额外的钙。在另一段时间内，该饮料每天将额外提供650毫克的钙，作为碳酸钙在一半的受试者中或在另一半的受试者中作为乳制品钙。将确定脂肪、能量、钙和蛋白质(氮)的平衡(摄入-排泄)。总能量消耗将使用双标记水和静息能量消耗来确定，饲养的热效应将使用间接量热法来确定。这项研究将评估钙/乳制品作为能量平衡的调节器，这对儿童的体脂管理很重要。

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.