1、1,能量（ENERGY）,一、概述（introduction）,1.能量单位,焦耳joule (J), 千焦耳kilojoules(kj) 兆焦耳卡calorie (cal), 千卡kilocalories(kcal) 1kcal4.184kj, 1kj0.239kcal , 1MJ=239kcal,2. 产能营养素及生热系数,carbohydrate 4kcal/g Protein 4kcal/g Lipid 9kcal/g Alcohol 7kcal/g,生热系数：每克产能营养素体内氧化产生的能量值。,2,二、人体的能量消耗 The body spends energy,3,(一)基础代谢
2、Basal Metabolism,1.定义 Definition,The energy needed to maintain life when a body is at complete rest after a 12-hour fast (禁食).,是在安静和恒温（1825C)条件下，禁食12h后，静卧、放松而又清醒时的能量消耗。是维持人体最基本生命活动所必需的能量消耗。,4,2.基础代谢率 Basal metabolic rate, BMR,The rate of energy used for metabolism under basal condition, usually expr
3、essed as kcal per surface of body per hour (or kcal per kilogram body weight per hour),人体处于基础代谢状态下，每小时每平方米体表面积（或每公斤体重）的热能消耗。,5,3.基础代谢能量消耗的计算Calculation of BEE,BEE = 体表面积() BMR 24hBMR (refer to the table)体表面积() 0.00659身高 (cm) 0.0126体重(kg) 0.1603,1).体表面积法,6,表1-10 人体基础代谢率,引自营养与食品卫生学，第三版，第21页。,7,静息代谢率（R
4、esting Metabolic Rate, RMR ）energy expenditure of body under the rest after 4-hour fast.RMR is less then BMR.测定时全身处于休息状态，禁食仅需4小时。,8,表1-12 人体静息代谢参考值 (Kcal/ 24小时),摘自Nutrition Science and Application,第二版，第190页,1997。,9,2).公式计算法.Harris and Benedict formula,3). 体重计算法 The method suggested by WHO: refer to
5、the Table,BEE(man)66.47+13.75体重(kg)+5.0身高(cm) - 6.76年龄(y) BEE(woman)65.50+9.46体重(kg)+ 1.85身高(cm) - 4.68年龄(y),10,WHO 建议的计算基础代谢公式（kcal/d),注:W为体重(kg)。摘自Technical Report Series724,Geneva,WHO,1985。,中国营养学会建议18岁人群按该公式的计算结果减去5%。,11,4. 基础代谢的影响因素The factors affecting BMR,(1) 体格(Body surface area): (or lean ma
6、ss fatty tissue)(2) 性别(Gender): male female (3) 年龄(Age): 2% of decline per 10 years after age 30 5% of decline per 10 years after age 60 (4) 营养状况(Nutrition state): Low energy intake decreases BMR about 10%-20% (5) 生理状况(Physiological status): Pregnancy increases BMR (6) 体温(Body temperature): Fever in
7、creases BMR (7) 环境条件High or low air temperature, hormone system activity, nerve and eating too much increase BMR (Adaptive Thermogenesis , 适应性生热作用),12,(二) 体力活动 Physical Activity,The energy needed during physical activity depends on body lean mass, intensity (强度) ，body weight and time of activity. 通常
8、各种体力活动所消耗的能量占人体总能量消耗的15%30%。 体力活动水平（PAI，physical activity level)指一人1天24小时消耗的总能量与其基础代谢能量之比值，最好能达到1.75以上。,13,日常活动能量消耗,14,(三) Specific dynamic action (or Thermic Effect of Food, TEF)食物特殊动力作用或食物热效应,1. Definition,The amount of extra energy used by body during digestion, absorption, metabolism, and storag
9、e of energy-yielding nutrients. 因摄食而引起的能量额外消耗,2. Energy expenditure,5%-6% of total calorie produced by carbohydrates,carbohydrates,lipids,4%-5% of that,protein,30-40% of that,mixed food,10% 0f total energy consumed（消耗）,15,（四）生长发育和新组织增加,婴幼儿、儿童、青少年生长发育孕妇的子宫、乳房、胎盘、胎儿的生长发育及体脂储备乳母合成和分泌乳汁恢复期病人,16,(一) calc
10、ulation (计算法),三、人体一日能量需要量的确定 Estimating energy requirements,能量消耗的计算（calculating the total energy expenditure ）,basal metabolism physical activities specific dynamic action,能量需要量（ energy requirements ）是维持人体正常生理功能所需要的能量。人体能量的需要量实际就是能量的消耗量。,17,2. Dietary survey（膳食调查),健康者在食物供应充足、体重不发生明显变化时，其能量摄入量基本上可反映出
11、能量需要量。可对一定数量的对象进行膳食调查，计算出调查对象平均每日摄入食物的总能量，间接估算出人群的能量需要量。,18,(二) measuring energy use by body（测量法),1. Direct calorimetry(直接测热法) A method of determining a bodys energy use by measuring heat that emanates（散发） from the body, usually using an Insulated chamber（绝热仓）,2. Indirect calorimetry(间接测热法),A method
12、 of measuring a bodys energy use by measuring its oxygen uptake (and often carbon dioxide output as well) and then using formulas to convert that gas exchange into energy use. The newest method is stable isotopes(稳定同位素) of oxygen and hydrogen. This method is quite accurate but very expensive.,19,四、热
13、能推荐摄入量 Energy RNI,中国居民膳食能量推荐摄入量(RNIs),20,（续表）中国居民膳食能量推荐摄入量(RNIs),21,（续表）中国居民膳食能量推荐摄入量(RNIs),注：AI,非乳母喂养应增加20%。,22,（续表）中国居民膳食能量推荐摄入量(RNIs),23,五、Health and energy intake,(一)the risk of excessive energy,obesity(肥胖): diabetes（糖尿病）, hypertension（高血压）, cardiovascular disease（心血管疾病）, sleep apnea(窒息) osteoar
14、thritis（骨关节炎）, abdominal hernias（疝气）, some cacers, varicose veins（静脉曲张）, gout（痛风）, gallbladder disease（胆囊疾病）, arthritis（关节炎）, respiratory problems (including Pickwickian syndrome, a breathing blockage linked with sudden death), liver malfunction, complications in pregnancy and surgery, flat feet, an
15、d even a high accident rate.,24,The costs of these obesity-related illnesses were estimated at more than $39 billion in 1986 in USA. People with BMI greater than 35 are twice as likely to die prematurely（过早） as others.,(二) Energy restriction （限制热能摄入）,It is beneficial to prevention of many diseases especially for old people, and prolonging life.,25,小 结,人体利用食物中的产能营养素蛋白质、脂肪、碳水化合物提供能量。人体每日能量消耗主要由基础代谢、体力活动、食物热效应构成。对于某些特殊人群，能量消耗还包括生长发育和新组织增加。人体一日能量需要量可以通过计算法和测量法来确定。能量过多或过少即能量平衡失调会引起一系列健康问题。,26,思考题,1.名词解释：生热系数、基础代谢、静息代谢率、食物热效应、体力活动水平（PAL）2.人体能量消耗包括哪些方面及特点3.测定人体能量消耗的方法有哪些？4.能量平衡对机体有何重要意义？,
