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Energy balance. Body composition measurement. Gold standard: hydrostatic (underwater) Skinfolds: accurate when taken properly Several sites, converted to %fat by equations Bioelectrical impedance analysis Based on resistance to electrical current Affected by alcohol, exercise, meal/water
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Exer Nutr c11-weight Energy balance
Exer Nutr c11-weight Body composition measurement • Gold standard: hydrostatic (underwater) • Skinfolds: accurate when taken properly • Several sites, converted to %fat by equations • Bioelectrical impedance analysis • Based on resistance to electrical current • Affected by alcohol, exercise, meal/water • Dual energy X-ray absorptiometry (DEXA) • Clinical standard for measuring bone density • 2 different intensities, can distinguish soft tissues, bones, muscles, fat • Affected by hydration status
Exer Nutr c11-weight Body composition measurement • Computed tomography (CT) • Qualitative and quantitative info about total area of tissue, thickness and volume of tissues within organ • Fat surrounding tissue, fat within tissue • Magnetic resonance imaging (MRI) • Similar to results of CT, but use elctromagnetic radiation rather than ionizing radiation • Air displacement plethysmography • Same principle as hydrostatic, but use air rather than water
Exer Nutr c11-weight Normal range of body weight and fat • Essential body fat • ~3% BW for men, ~12% for women • General body fat • 12-15% for young men, 25-28% for young women • NO body fat standard for athletes • Ideal body composition highly dependent on particular sport
Exer Nutr c11-weight Genetics on body weight • Estimated 25-40% adiposity result of genes • >250 genes potential to influence body fatness • Identical twins: variation within pairs << variations between pairs • Under energy surplus or deficiency
Exer Nutr c11-weight Weight loss • NO lower than essential fat • Realistic weight loss ~1 kg every 2 weeks • Reduce 500 kcal/day • Energy and substrate balance • ↑oxidation rate of CHO and protein immediately when excess amounts ingested, not fat • Excess fat consumption: no increase in oxidation rate, no conversion to CHO or protein, storage • Fat: energy dense, usually taste good • Fat efficiently stored, require very little energy for digestion • ↓dietary fat effective for weight loss
Exer Nutr c11-weight Common mistakes for weight loss • Trying to lose weight too rapidly • Mostly dehydration • Weight loss without performance loss has to occur slowly • Trying to lose weight during on-season • Underperformance: hard training is difficult when energy intake reduced • Weight loss best accomplished during off-season • Not eating breakfast or lunch • Increase hunger feelings, may eat more • Too little CHO intake • Provide energy for training, protein-sparing
Exer Nutr c11-weight ‘Set point’ theory • Body has a weight ‘set point’ • Maintenance of reduced or elevated body weight associated with compensatory changes in energy expenditure (BMR) • Weight cycling: yo-yo effect • After weight loss, it is regained in relatively short time
Exer Nutr c11-weight Gender difference • Weight loss after aerobic exercise training: greater effect for males • Women store more fat in gluteal-femoral region, men in visceral (abdominal) region • Fat in upper body and abdominal region more metabolically active, higher rate of lipolysis in response to adrenergic stimulation • During exercise, FA preferentially mobilized from upper body and abdominal region • Women greater resistance to weight loss
Exer Nutr c11-weight Weight-loss methods • Energy and fat restriction • Maintain reasonable glycogen stores • Very-low-energy diets • 400-800 kcal/d, usually liquid meals • ↑fat oxidation ketosis • protein loss for gluconeogenesis • High-protein diets • ↑sensation of satiety, ↑thermic effect of feeding • Zone diets: 40en% CHO, 30% fat, 30% protein • 1000-2000 kcal/d, low energy • Claimed to ↓insulin, ↑lipolysis, ↑favorable eicosanoids little scientific evidence • Low-CHO diet: ketogenic, Atkins diet • ↑ Ketone bodies ↓appetite, loss of energy in urine (100-150 kcal/d) • Relatively high fat, ↓glycogen
Exer Nutr c11-weight Exercise to lose weight • Combine exercise and diet: most effective way to maintain lower body weight after weight reduction • Exercise intensity? • Fat oxidation inhibited > 75% VO2max, but higher energy expenditure • Max rate of fat oxidation 55-65% VO2max • Resistance training help to prevent reduction in BMR • Resistance training at least as effective as aerobic exercise in reducing body fat
Exer Nutr c11-weight Caloric reduction + walking / jogging, Obese female
Exer Nutr c11-weight Weight cycling in athletes • Repeated cycles of weight loss and weight gain • basal metabolic rate, more difficult to lose weight • Plasma concentrations: albumin, prealbumin, retinal binding protein • body protein status • Reduce the numbers of making weight • Select the appropriate weight class • Maintain appropriate body weight • Compete in higher class in less important games
Exer Nutr c11-weight Guidelines for weight loss • Determine realistic body-weight goal • Lose no more than 0.5 kg/week • Eat more fruits, vegetables • Low-fat snacks • Study food labels, avoid high-fat food • Limit fat add-ons • 5-6 smaller meals • Avoid eating very large meals • High CHO intake, consume CHO immediately after training • Miltivitamin and mineral supplements helpful
Exer Nutr c11-weight Making weight • Dehydration: detrimental to performance and dangerous • ↓plasma volume, hyperthermia • Gaining weight: energy intake > expenditure • ↑CHO intake, not fat intake • Realistic 0.2-1 kg/week • Protein synthesis is slow process
Exer Nutr c11-weight Study results - 1 • 角力選手，分別使用高醣(70%熱量來自醣類)或低醣(55%)的低熱量飲食 • 21.9 kcal/kg無脂肌質/day , 7天後 • 低醣組在Wingate test的總功輸出較節食前顯著降低(-7%) • 高醣組則在節食前後無顯著差異 • 在經過4天的節食而減少約6%的體重後，使用高醣飲食(65.9%)的受測者在6分鐘間歇性高強度的手部腳踏車測試所做的總功與節食前無顯著差異 • 使用低醣飲食(41.9%)者則較節食前顯著降低
Exer Nutr c11-weight Study results - 2 • 角力選手: 低熱量配方飲食72小時後 • (18 kcal/kg體重，60%熱量來自醣類，20%蛋白質，20%脂肪), 流失3.3%原體重 • 接下來的150分鐘，給予21 kcal/kg體重的營養補充 • 分為高醣(75%醣類，10%蛋白質，15%脂肪)與低醣(47%醣類，16%蛋白質，37%脂肪)兩組 • 在節食前(test 1)、節食後(test 2)、和開始補充5小時後(test 3)，以固定式手部腳踏車進行4.5分鐘的間歇最高強度測試 • 兩組 test 2的總功(total work) < test 1 • 高醣組在test 3總功已恢復到 test 1的99.1% • 低醣組在test 3總功為 test 1的91.5%，且與test 2相似
Exer Nutr c11-weight Study results - 3 • Case study of an elite male wrestler • 1. making weight to 52 kg • 熱量攝取從平均每天約2070 kcal減少至1900 kcal • 62%醣類，20%蛋白質，18%脂肪 • 54.88公斤(體脂肪4.8%) 53.25公斤(體脂肪3.8%) • 在比賽前再脫水1.4公斤而達到52公斤 • 2. 17天內降至50.59公斤(體脂肪1.1%) • Energy intake 自1831 kcal/d降至比賽前三天的1153 kcal/d • 醣類62-65%，蛋白質23-26%，脂肪11% • 比賽前再脫水2.73公斤而達到48公斤的參賽標準 • 肌力與有氧能力仍維保持與降體重前相當
Exer Nutr c11-weight 降體重期間的營養 • High protein, high CHO, very low fat • ~ 2 g protein/kg • 飯 麵或麵包一定要吃: 提供足夠醣類 • 減少脂肪攝取 • 去皮 去油 不喝湯 不吃炸煎的食物 過水 脫脂奶或優酪乳 • 每天吃一顆綜合維他命 • 過磅前約一星期 減少鹽份攝取 避免水份堆積 • 儘量少吃各種調味料 醬油 醬汁 可加少許胡椒或醋 • 儘量少吃醃製的食品和零食 • 停止使用肌酸 • 過磅前1-2天少吃高纖維的食物 避免殘留腸道中 • 避免 早餐營養穀片 全麥麵包 豆類 花椰菜 芹菜 蘆筍
Exer Nutr c11-weight 可使用的營養補充品 • BCAA, beta-hydroxy-beta-methylbutyrate (HMB), may helpful • 飯+水果+(脫脂牛奶)+健怡美而力 +HMB • 善存1-2顆 • 75% CHO, 2-3 g protein /kg BW • 120 g protein = 480 kcal • 2500 –480 = 2000 kcal = 500 g CHO , ~8 g/kg • 720/1200 = 60% CHO
Exer Nutr c11-weight 過磅後的營養補充 • 若過磅後1-2小時即要比賽 • 過磅後迅速補充碳水化合物 包括香蕉 麵包 約20-30分鐘一次 （先試驗 避免腸胃不適） • 其他水果 果汁含果糖 可能引起腸胃不適 • 注意水份的攝取 至少需補充至過磅前體重(或適量） • 比賽前10-15分鐘喝200-300 ml 運動飲料（先試驗 避免低血糖） • 若過磅後隔天才比賽 • 過磅後迅速補充碳水化合物包括香蕉 蘋果 果汁 麵包 運動飲料 • 避免大吃大喝 應該分散成數餐 或每隔2-3小時吃一次，但每次份量不要太多 • 少吃油脂和肉類 以飯 麵包 水果為主
Exer Nutr c11-weight New drugs for weight reduction • liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, approved by FDA in December, 2014 • Via injection • Previously approved for treatment of type 2 diabetes • GLP1R is known to be expressed in pancreaticbeta cells. Activated GLP1R stimulates the adenylyl cyclase pathway which results in increased insulin synthesis and release of insulin
