Regulators of Food Intake

能量摄入是能量平衡方程中最难测量的部分。 使用病人电脑自动售货机系统，食物摄入量已超过180人。在接受研究超过一次的个体中，组内相关系数非常高（r=0.9），表明这些研究尽管在住院患者中进行，但具有很高的重现性。 在夜间进食是一种可能使个体易患肥胖症的行为。在我们的自动售货机研究中，我们发现近30%的志愿者在夜间从我们的自动售货机中进食。这些人在3年的随访期内消耗了更多的卡路里，体重增加了更多。 此外，这些个体在我们的呼吸室中测得的呼吸阻力较高，而体重维持饮食表明食物摄入的动力增加。未来的努力将研究是否有差异，在促食欲或食欲激素之间的夜间进食者和非夜间进食者。 较高的呼吸商，即碳水化合物氧化与脂质氧化的比率，已知可预测体重增加。这种体重增加的机制被认为是继发于这些个体中较低的脂质氧化。在体重维持期间测得的较高呼吸商也可预测在自由进食自动售货机研究期间的食物摄入量。然而，最能预测食物摄入的呼吸商的组成部分是较高的碳水化合物氧化，表明碳水化合物（可能是糖原）平衡在短期食物摄入调节中的作用。为了进一步评估这一点，我们的食物摄入研究中增加了一个额外的组，该研究将在维持体重低碳水化合物和低脂肪饮食3天后检查食物摄入量。 过去食物摄入量的预测表明，空腹饥饿激素浓度较低的人（一种与食物摄入量增加有关的激素）实际上吃得更多。 然而，对一个更大的个体群体的后续研究并没有显示总ghrelin浓度和食物摄入量之间有任何联系。此外，总生长激素释放肽浓度并没有减少与过度喂养，生长激素释放肽浓度的变化并不能预测随后的食物摄入量。这些数据表明，生长激素释放肽可能在控制日常食物摄入方面没有作用，也不会被暴饮暴食所抑制。为了进一步评估这一点，另一个研究组正在评估与体重维持饮食期相比，在固定的3天过度喂养期后总生长素和活性生长素释放肽浓度的影响。还在过度喂养和禁食期间评估身体活动、能量消耗和基础体温，并在每个饮食期后评估随意食物摄入。

Energy intake is the most difficult part of the energy balance equation to measure. Using an in patient computerized vending machine system, food intake has been measured over 180 individuals. In individuals undergoing the study more than once the intra-class correlation coefficient is very high (r=0.9) indicating that these studies although performed in an inpatient setting are very reproducible. Eating during nighttime hours is a behavior that may predispose individuals to obesity. In our vending machine studies, we found that nearly 30% of volunteers ate from our vending machines during the night. These individuals consumed overall more calories and gained more weight over a 3 year follow-up period. In addition, these individuals have higher respiratory quotients measured in our respiratory chamber while on a weight maintenance diet indicating an increased drive for food intake. Future efforts will examine whether there are differences in anorexigenic or orexigenic hormones between night eaters and non-night eaters. Higher respiratory quotient, the ratio of carbohydrate oxidation to lipid oxidation, is known to predict weight gain. The mechanism of this increase in weight was thought to be secondary to a lower lipid oxidation in these individuals. Higher respiratory quotient measured during weight maintenance also predicted food intake during the ad-libitum vending machine study. However the component of respiratory quotient which best predicted food intake was higher carbohydrate oxidation indicating a role for carbohydrate (likely glycogen) balance in the regulation of short term food intake. To further evaluate this, an additional arm has been added to our food intake study, which will examine food intake following 3 days of both a weight maintenance low carbohydrate and low fat diet. Predictors of food intake in the past have demonstrated that individuals with lower fasting ghrelin concentrations (a hormone which is associated with increased food intake) actually ate more. However, follow-up studies on a larger group of individuals did not show any association between total ghrelin concentrations and food intake. Furthermore, total ghrelin concentrations did not decrease with overfeeding, and change in ghrelin concentration did not predict subsequent food intake. This data indicates that ghrelin may not have a role in control of day to day food intake, nor is it suppressed by overeating. In order to evaluate this further, another study arm is evaluating the effect of both total and active ghrelin concentrations following a period of fixed 3 day period overfeeding compared to a period of weight maintenance diet. Physical activity, energy expenditure, and basal body temperature are also evaluated during both overfeeding and fasting, and ad libitum food intake is evaluated following each diet period.