Within-day variation of bioelectrical resistance measurements in patients with chronic obstructive pulmonary disease

The relative contribution of a meal, exercise and diuretic therapy to within day variation of resistance values from bioelectrical impedance measurements was studied in several groups of patients with severe Chronic Obstructive Pulmonary Disease (COPD). All patients were in a stable clinical condition. Fasting resistance (RES) in the early morning was significantly higher than RES values during the day ((mean +/- SD): 26 +/- 21 Ohms, p < 0.001). Relative to a non-fasting pre-meal value no significant decrease in RES was measured within 4h after ingestion of the meal. RES did not change significantly after a submaximal exercise challenge on the bicycle ergometer. No consistent effect of oral diuretics (40mg furosemide), was established within 5h after administration. Measurements on two consecutive days at the same time in the nourished state, were highly reproducible: mean change 4 +/- 20 Ohms, NS). We conclude that in patients with stable COPD, within day variation has only a slight impact on the estimation of fat free mass for between-patient comparison, but it is important to take this into account during follow up studies.     

Thermic effect of food during graded exercise in normal weight and obese men

The thermic effect of food during incremental cycle ergometer exercise was compared in six normal weight and six obese men (mean +/- SEM 104 +/- 5% and 160 +/- 11% ideal body weight, respectively). Graded exercise tests were performed after a 12-h fast and 60 min after the start of a 910 kcal mixed meal, on separate days. The thermic of food during exercise, which is the fed minus the fasting oxygen consumption (VO2), was significantly greater for the normal than the obese men at submaximal intensities from O (unloaded cycling) to 100 W (p less than 0.05). The mean slope of the regressions of VO2 (ml . min-1) on power output (W), which reflects the rate of increase in energy expended relative to increases in external work performed, did not differ significantly between the fed and fasting conditions for either group, but the mean (+/- SEM) intercept was significantly higher for the normal, but not the obese men, in the fed than the fasting state (599 +/- 53 versus 497 +/- 47 ml O2 . min-1 for the normal men and 819 +/- 126 versus 821 +/- 145 ml O2 . min-1 for the obese men). These results indicate that the thermic effect of food during exercise, which is virtually absent in the obese men, does not increase significantly across submaximal power outputs for the normal men and therefore does not reflect a significant reduction in efficiency.     

Bioelectrical impedance: effect of 3 identical meals on diurnal impedance variation and calculation of body composition

BACKGROUND: Bioelectrical impedance analysis (BIA) can be used for estimating body composition. Earlier studies showed that the ingestion of meals lowers bioelectrical impedance, but none studied the effect of repeated ingestion of an identical meal in narrow intervals on impedance measurements during 24 h. OBJECTIVES: The objectives were to study the effect on bioelectrical impedance of 3 identical meals and to compare the results from single-frequency BIA measurements with those from multiple-frequency BIA measurements. DESIGN: Bioelectrical impedance was measured 18 times during 24 h in 18 healthy subjects [10 women and 8 men; x +/- SD age: 31.5 +/- 11.7 y; body mass index (in kg/m(2)): 22.2 +/- 2.7]. An identical meal was given at breakfast, lunch, and dinner. RESULTS: Bioelectrical impedance decreased after ingestion of a standard meal (P < 0.05). The decrease in impedance lasted 2-4 h after each meal. The decrease was additive during the day, although it was more pronounced after the first meal because of the combined effect of rising from the supine position and meal ingestion. This is an important consideration when calculating body composition: percentage of body fat varied by 8.8% from the highest to the lowest measurement in women and by 9.9% from the highest to the lowest measurement in men. The bioelectrical impedance at 50 kHz was identical when measured with multiple frequencies or a single frequency. CONCLUSION: The ingestion of meals leads to an additive decrease in bioelectrical impedance and thus to a decrease in the calculated percentage of body fat.     

Short-term creatine supplementation improves maximum quadriceps contraction in women

Creatine monohydrate (CrH2O) supplementation has been demonstrated to increase skeletal muscle power output in men. However, its effect upon women is not as clearly defined. This study investigated the effect of oral creatine supplementation upon muscle function, thigh circumference, and body weight in women. Twenty-two consenting college-age women were assigned to 1 of 2 groups matched for dietary and exercise habits, phase of menstrual cycle, and fat-free mass (FFM). After familiarization with testing procedures, pretrial measures of muscle function (5 repetitions 60 deg x s(-1) and 50 repetitions 180 deg x s(-1) were conducted during maximal voluntary concentric contraction of the preferred quadriceps muscle using an isokinetic dynamometer. Subjects then ingested 0.5 g x kg(-1) FFM of either CrH2O or placebo (one fourth dosage 4 times daily) in a double-blind design for 5 days. Resistance exercise was prohibited. After the ingestion phase was completed, all measures were repeated at the same time of day as during pretrials. Statistical analysis revealed time to peak torque in quadriceps extension decreased from pre-test values of 255 +/- 11 ms (mean +/- SEM) to post-test values of 223 +/- 3 ms; average power in extension increased from 103 +/- 7 W pre-test to 112 +/- 7 W post-test; and, during flexion, average power increased from 59 +/- 5 W pre-test to 65 +/- 5 W post-test in the creatine group as compared to controls (p .05). FFM, percent body fat, mid-quadriceps circumference, skinfold thickness of the measured thigh, and total body weight did not change for both groups between trials. We conclude that CrH2O improves muscle performance in women without significant gains in muscle volume or body weight.     

Effects of a longitudinal training program on responses to exercise in overweight men

OBJECTIVE: The aim of this study was to determine how training modifies metabolic responses and lipid oxidation in overweight young male subjects. RESEARCH METHODS AND PROCEDURES: Eleven overweight subjects were selected for a 4-month endurance training program. Before and after the training period, they cycled for 60 minutes at 50% of their VO(2)max after an overnight fast or 3 hours after eating a standardized meal. Various metabolic and endocrine parameters, and respiratory exchange ratio values were evaluated. RESULTS: Exercise-induced plasma norepinephrine concentration increases were similar before and after training in fasted or fed conditions. After food intake, exercise promoted a decrease in plasma glucose and a higher increase in epinephrine than in fasting conditions. The increase in epinephrine after the meal was more marked after training (264 +/- 32 vs. 195 +/- 35 pg/mL). Training lowered the resting plasma nonesterified fatty acids. During exercise, changes in glycerol were similar to those found before training. Lipid oxidation during exercise was higher in fasting than in fed conditions (15.5 +/- 1.4 vs. 22.3 +/- 1.7 g/h). Training did not significantly increase fat oxidation when exercise was performed in fed conditions, but it did in fasting conditions (18.6 +/- 1.4 vs. 27.2 +/- 1.8 g/h). DISCUSSION: Endurance training decreased plasma nonesterified fatty acids, cholesterol, and insulin concentrations. Training increased lipid oxidation during exercise, in fasting conditions, and not when exercise was performed after the meal. During exercise in overweight subjects, the fasting condition seems more suited to oxidizing fat and maintaining glucose homeostasis than a 3-hour wait after a standard meal.     

A low glycemic index meal before exercise improves endurance running capacity in men

This study investigated the effects of ingesting a low (LGI) or high (HGI) glycemic index carbohydrate (CHO) meal 3 h prior to exercise on endurance running capacity. Eight male recreational runners undertook two trials (LGI or HGI) which were randomized and separated by 7 d. After an overnight fast (12 h) the subjects ingested either a LGI or HGI meal 3 h prior to running at 70% VO2max until exhaustion. The meals contained 2 g/kg body mass CHO and were isocaloric and iso-macronutrient with calculated GI values 77 and 37 for the HGI and LGI respectively. The run times for the LGI and HGI trials were 108.8 +/- 4.1 min and 101.4 +/- 5.2 min respectively (P = 0.038). Fat oxidation rates were higher during exercise after the LGI meal than after the HGI meal (P < 0.05). In summary, ingestion of a LGI meal 3 h before exercise resulted in a greater endurance capacity than after the ingestion of a HGI meal.     

A comparison of effects of fish and beef protein on satiety in normal weight men

BACKGROUND: Previous studies have indicated that fish protein may have a greater effect on satiety compared to other protein sources of animal origin.OBJECTIVE: To compare the effects of fish protein and beef protein meals on hunger and satiety. DESIGN: Twenty-three normal non-smoking, healthy males aged 20-32 years, body mass index 22.5+/-1.8 (s.d.) kg/m(2) participated in a study, with within-subjects design and 1 week between test days. In the morning of the test days, subjects received a standardized breakfast. Four hours after breakfast, subjects were served an iso-energetic protein-rich (40 energy % protein) lunch meal, consisting of either a fish protein dish or a beef protein dish. Four hours after the start of the lunch meals, an ad libitum standardized evening meal was served and the intake of food was measured. Appetite was rated by visual analogue scales (VAS) immediately before and after the meals, as well as every hour between the meals. After the evening meal until bedtime, subjects were asked to record in detail foods and drinks consumed. RESULTS: The repeated VAS-ratings of hunger, satiety and prospective consumption were modelled in a random effects model, taking pre-lunch VAS-ratings into account. After the fish meal, the point estimates were lower for hunger (-2+/-4.8), higher for satiety (8.7+/-6.0) and lower for prospective consumption (-4.9+/-4.7), but they did not reach statistical significance (P satiety=0.88; P hunger=0.15; P prospective=0.30). However, the energy intake at the evening meal displayed significant differences with subjects eating less after the fish protein lunch (2765 vs 3080 KJ, P<0.01) without feeling less satiated. No later energy compensation after the evening meal was found on the test day. CONCLUSION: Although no significant differences in VAS-ratings of satiety or hunger were detected, subjects displayed an 11% reduction in energy intake at the subsequent evening meal.     

Response of albumin synthesis to oral nutrients in young and elderly subjects

BACKGROUND: The synthesis of albumin after oral ingestion of nutrients provides a means of storing amino acids, which can be made available during periods of fasting. OBJECTIVE: This study was undertaken to see whether the response of albumin synthesis to the oral intake of nutrients is compromised in elderly subjects. DESIGN: Albumin synthesis was determined from the incorporation of 43 mg l-[(2)H(5)]phenylalanine/kg body wt. Eight elderly subjects (aged >60 y) and 8 young subjects (aged 21-35 y) were studied on 3 separate occasions: after the intake of water, a liquid meal (with 15% of energy from protein, 30% of energy from fat, and 55% of energy from carbohydrate), or an isonitrogenous but not isocaloric meal containing only protein. RESULTS: Mean (+/-SEM) albumin synthesis, expressed as an absolute rate (ie, the amount of albumin synthesized per day), was significantly lower in elderly subjects (108 +/- 7 mg . kg body wt(-1) . d(-1)) than in young subjects (141 +/- 7 mg . kg body wt(-1) . d(-1)). In response to the complete meal, albumin synthesis was significantly increased in both the elderly (144 +/- 7 mgkg body wt(-1) . d(-1)) and the young (187 +/- 11 mg . kg body wt(-1) . d(-1)) subjects. The protein component of the meal was sufficient to stimulate albumin synthesis in both the elderly (147 +/- 14 mg . kg body wt(-1) . d(-1)) and the young (182 +/- 6 mg . kg body wt(-1) . d(-1)) subjects. CONCLUSIONS: Elderly subjects have lower rates of albumin synthesis than do young subjects during fasting, but they stimulate albumin synthesis proportionately in response to the oral ingestion of protein. The intakes of additional fat and carbohydrate do not stimulate albumin synthesis further.     

Aging does not impair the anabolic response to a protein-rich meal

BACKGROUND: Sarcopenia is a debilitating condition afflicting the elderly that may be facilitated by insufficient or ineffectual intake of dietary protein. We previously showed that free-form essential amino acids acutely stimulate muscle protein synthesis in both the young and the elderly. However, the ability of an actual protein-rich food to stimulate anabolism in the young and the elderly has not been explored. OBJECTIVE: We aimed to characterize changes in plasma amino acid concentrations and to quantify muscle protein synthesis in healthy young (41 +/- 8 y old; n = 10) and elderly (70 +/- 5 y old; n = 10) persons after ingestion of a 113-g (4-oz) serving of lean beef. DESIGN: Venous blood samples and vastus lateralis muscle biopsy samples were obtained during a primed (2.0 mumol/kg) constant infusion (0.08 mumol.kg(-1).min(-1)) of l-[ring-(13)C(6)] phenylalanine. Plasma amino acid concentrations were measured and a mixed-muscle fractional synthesis rate (FSR) was calculated during the premeal period and for 5 h after beef ingestion. RESULTS: Mixed-muscle FSR increased by approximately 51% in both the elderly (mean +/- SE measurements: 0.072 +/- 0.004%/h and 0.108 +/- 0.006%/h before and after the meal, respectively) and the young (0.074 +/- 0.005%/h and 0.113 +/- 0.005%/h before and after the meal, respectively) after beef ingestion (P < 0.001). Plasma amino acid concentrations peaked at approximately 100 min after beef ingestion in both age groups but were substantially higher in the elderly (2185 +/- 134 nmol/mL compared with 1403 +/- 96 nmol/mL; P < 0.001). CONCLUSION: Despite differences in the concentration of amino acids in the plasma precursor pool, aging does not impair the ability to acutely synthesize muscle protein after ingestion of a common protein-rich food.     

The effect of a high carbohydrate meal on endurance running capacity

This study examined the effects of a pre-exercise meal and a carbohydrate-electrolyte solution on endurance running capacity. Ten men performed 3 treadmill runs at 70% VO2max to exhaustion after consuming (a) a carbohydrate meal 3 h before exercise and a carbohydrate-electrolyte solution during exercise (M + C); or (b) the carbohydrate meal 3 h before exercise and water during exercise (M + W); or (c) a liquid placebo 3 h before exercise and water during exercise (P + W). Exercise time was longer in M + C (125.1 +/- 5.3 min; mean +/- SE) and M + W (111.9 +/- 5.6 min) compared with P + W (102.9 +/- 7.9 min; p < .01 and p < .05, respectively), and longer in M + C compared with M + W (p < .05). Serum insulin concentration at the start of exercise and carbohydrate oxidation rates during the first hour of exercise were higher, whereas plasma FFA concentrations throughout exercise were lower in M + W and M + C than in P + W (p < .01). A carbohydrate meal before exercise at 70% VO2max improved endurance running capacity; however, the combination of the meal and a carbohydrate-electrolyte solution during exercise further improved endurance running capacity.     

Effect of glycerol-induced hyperhydration on thermoregulation and metabolism during exercise in heat

This study examined the effect of glycerol ingestion on fluid homeostasis, thermoregulation, and metabolism during rest and exercise. Six endurance-trained men ingested either 1 g glycerol in 20 ml H2O x kg(-1) body weight (bw) (GLY) or 20 ml H2O x kg(-1) bw (CON) in a randomized double-blind fashion, 120 min prior to undertaking 90 min of steady state cycle exercise (SS) at 98% of lactate threshold in dry heat (35 degrees C, 30% RH), with ingestion of CHO-electrolyte beverage (6% CHO) at 15-min intervals. A 15-min cycle, where performance was quantified in kJ, followed (PC). Pre-exercise urine volume was lower in GLY than CON (1119 +/- 97 vs. 1503 +/- 146 ml x 120 min(-1); p < .05). Heart rate was lower (p < .05) throughout SS in GLY, while forearm blood flow was higher (17.1 +/- 1.5 vs. 13.7 +/- 3.0 ml x 100 g tissue x min(-1); p < .05) and rectal temperature lower (38.7 +/- 0.1 vs. 39.1 +/- 0.1 degrees C; p < .05) in GLY late in SS. Despite these changes, skin and muscle temperatures and circulating catecholamines were not different between trials. Accordingly, no differences were observed in muscle glycogenolysis, lactate accumulation, adenine nucleotide, and phosphocreatine degradation or inosine 5'-monophosphate accumulation when comparing GLY with CON. Of note, the work performed during PC was 5% greater in GLY (252 +/- 10 vs. 240 +/- 9 kJ; p < .05). These results demonstrate that glycerol, when ingested with a bolus of water 2 hours prior to exercise, results in fluid retention, which is capable of reducing cardiovascular strain and enhancing thermoregulation. Furthermore, this practice increases exercise performance in the heat by mechanisms other than alterations in muscle metabolism.     

Effect of growth hormone on the glomerular filtration response to a protein meal

The role of dietary protein intake in the pathogenesis of progressive renal disease has been recently reexamined. Studies of both animal and humans with chronic renal disease have shown that restriction of dietary protein may slow the progression of the decline in renal function. This occurs because of a decrease in intraglomerular blood flow and pressure. The mechanism of this phenomenon is not known. The effect of protein intake on renal function is thought to be hormonally mediated. Since growth hormone can increase renal blood flow as well as GFR, we tested the hypothesis that the presence of growth hormone is necessary for the increase in glomerular filtration rate (GFR) seen after the ingestion of a protein meal. We evaluated the change in GFR after a standardized mixed protein meal in 13 patients with growth hormone deficiency. Neither basal creatinine clearance after an overnight fast (76 +/- 17 ml/min/m2; mean +/- SD) nor maximum increment after a 50 g/m2 protein meal (33 +/- 11 ml/min/m2) differed in these growth hormone-deficient patients from 16 normals controls (76 +/- 18 and 30 +/- 15 ml/min/m2, respectively). Twelve hours after an injection of exogenous growth hormone, 0.06 mg/kg up to a maximum of 5 mg, the GFR response to a protein meal did not differ from the pretreatment response (77 +/- 19 and 32 +/- 17 ml/min/m2, respectively). We conclude that the presence of physiologic amounts of growth hormone is not necessary for the GFR response to a standard protein meal.     

Postprandial thermogenesis at rest and during exercise in elderly men ingesting two levels of protein

Seven elderly male subjects (69 +/- 3 yr, 67.8 +/- 9.2 kg, 24.5 +/- 3.6% body fat) lived for 12 consecutive weeks in a metabolic unit and maintained their weight with two different diets fed for 6 weeks each: Diet A, consisted of their habitual protein intake as determined on the outside by a dietary record (mean +/- SD, 1.12 +/- 0.22 g/kg d). Diet B was an isocaloric diet with reduced protein intake (70 mgN/kg d, i.e., 0.44 g protein/kg d) at the level of physiological protein requirement [7]. After 3 weeks on each diet, the thermogenic response to single meals A and B containing 38% of weight maintenance energy for each subject (731-994 kcal) was studied by indirect calorimetry under two situations: (1) at rest over a 4 hr period and (2) during graded exercise on a bicycle ergometer at four stepwise workloads (0,80, 200, and 300 kg/min). A postabsorptive control exercise was also performed in order to assess the net effect of the meal during exercise. Eating alone increased the energy expenditure by +0.18 +/- 0.07 kcal/min with meal A and +0.13 +/- 0.06 kcal/min with meal B. There was a positive correlation (r = 0.84, p less than 0.01) between the % energy derived from protein and the thermogenic response expressed as % of the energy content of test meal. Exercise failed to influence the thermogenic response to meals since the overall net increase in energy expenditure induced by the meals while exercising was not different from that obtained at rest: +0.22 +/- 0.17 kcal/min and +0.15 +/- 0.13 kcal/min with meal A and meal B, respectively. This study failed to show any interaction between exercise and postprandial thermogenesis in elderly individuals.     

中小学教师代谢综合征影响因素分析

目的 了解中小学教师代谢综合征(MS)发病及其影响因素。方法 采用横断面调查方法,随机抽取芜湖市中小学教师2 026名,进行问卷调查、体格检查和实验室检测,并运用Logistic回归分析代谢综合征影响因素。结果 不同性别的中小学教师在受教育程度、牛奶摄入、水产品摄入和饮茶习惯等方面的差异有统计学意义;其中受教育程度、体育锻炼、水产品摄入和饮茶是保护因素,而年龄、工作紧张程度、糖的摄入可能是代谢综合征的危险因素。Logistic逐步回归分析结果提示,牛奶摄入、水产品摄入和饮茶是代谢综合征的保护因素,而年龄和糖摄入是代谢综合征的危险因素,其中牛奶摄入在250~1500 g/周(OR=0.731,95%CI=0.542~0.987),水产品摄入在250~1000 g/周(OR=0.720,95%CI=0.541~0.959)以及以前饮茶(OR=0.446,95%CI=0.255~0.779)和现在正在饮茶(OR=0.635,95%CI=0.458~0.883),对代谢综合征的保护作用明显,而糖摄入<=250 g/月时代谢综合征的患病的危险是不食用食糖的2倍(OR=2.084,95%CI=1.390~3.125)。结论 年龄和糖摄入是代谢综合征患病的危险因素,而牛奶、水产品和饮茶是代谢综合征的保护因素。     

Effect of fluid and food intake on the body composition evaluation of elderly persons

Background  Several studies have shown that liquid and food intake interfere with the evaluation of body composition in adults. However, since there are no reports about this interference in the elderly population, the need to fast for this evaluation may be dispensable. Objectives  The objective of the present study was to assess the influence of liquid and solid food on the measurement of body composition by bioelectrical impedance analysis (BIA) and by dual energy X-ray absorptiometry (DXA). Design  Forty-one male volunteers aged 62 to 87 years participated in the study. The subjects were submitted to evaluation of body composition by DXA and BIA under fasting conditions and 1 hour after the ingestion of breakfast (500 ml of orange juice and one 50 g bread roll with butter). Results  There was no significant difference in the variables fat-free mass (FFM) or fat mass (FM) between the fasting condition and the evaluation performed 1 hour after the meal as measured by BIA or DXA. There was also no significant difference when the same variables were compared between methods. Conclusion  In the present study, the ingestion of 500 ml orange juice and of one bread roll with butter by elderly subjects did not affect the results of the parameters of body composition determined by BIA or DXA. Thus, these exams could be performed without the rigor of fasting, often poorly tolerated by the elderly.     

Blood glucose responses to carbohydrate feeding prior to exercise in the heat: effects of hypohydration and rehydration

This study assessed the plasma glucose (PG) and hormonal responses to carbohydrate ingestion, prior to exercise in the heat, in a hypohydrated state versus partial rehydration with intravenous solutions. On separate days, 8 subjects (21.0 +/- 1.8 years; 57.3 +/- 3.7 ml x kg(-1) x min(-1)) exercised at 50% VO2max in a 33 degree C environment until a 4% body weight loss was achieved. Following this, subjects were rehydrated (25 ml x kg(-1)) with either: 0.45% IV saline (45IV), 0.9% IV saline (9IV), or no fluid (NF). Subjects then ingested 1 g x kg(-1) of carbohydrate and underwent an exercise test (treadmill walking, 50% VO2max, 36 degrees C) for up to 90 min. Compared to pre-exercise level (294 mg x dl(-1)), PG increased significantly (>124 mg x dl(-1)) at 15 min of the exercise test in all trials and remained significantly elevated for 75 min in NF, 30 min more than in the 2 rehydration trials. Although serum Insulin increased significantly at 15 min of exercise in the 45IV trial (7.2 +/- 1.2 vs. 23.7 +/- 4.7 mIU x ml(-1)), no significant differences between trials were observed. Peak plasma norepinephrine was significantly higher in NF (640 +/- 66 pg x ml(-1)) compared to the 45IV and 9IV trials (472 +/- 55 and 474 +/- 52 pg x ml(-1), respectively). In conclusion, ingestion of a small solid carbohydrate load prior to exercise in the 4% hypohydration level resulted in prolonged high PG concentration compared to partial IV rehydration.     

Caffeine ingestion increases the insulin response to an oral-glucose-tolerance test in obese men before and after weight loss

BACKGROUND: Caffeine ingestion decreases the insulin sensitivity index (ISI) for an oral-glucose-tolerance test (OGTT) and decreases insulin-induced glucose disposal in lean male subjects during a hyperinsulinemic clamp. OBJECTIVE: We examined the effects of caffeine ingestion on insulin and glucose homeostasis in obese men before and after a nutrition and exercise intervention. DESIGN: Nine sedentary, obese [body mass index (in kg/m(2)): 34.0 +/- 1.0] men who had refrained from exercise and caffeine ingestion for 48 h underwent 2 oral-glucose-tolerance tests (OGTTs). The subjects randomly received caffeine (5 mg/kg) or placebo 1 h before each OGTT. After a 12-wk nutrition and exercise intervention, during which time the subjects avoided dietary caffeine, the OGTTs were repeated. RESULTS: The intervention resulted in decreases (P < or = 0.05) in body weight (8.5 +/- 1.5 kg), percentage body fat (2.8 +/- 0.7%), and fasting glucose, insulin, and proinsulin concentrations and increases in the ISI for the placebo OGTT (P < or = 0.05). Caffeine caused a greater (P < or = 0.05) OGTT insulin response and a lower (P < or = 0.05) ISI both before and after weight loss. The proinsulin-insulin ratio indicated that neither weight loss nor caffeine affected the nature of the beta cell secretion of insulin. CONCLUSIONS: A nutrition and exercise intervention improved, whereas caffeine ingestion impaired, insulin-glucose homeostasis in obese men. The results are consistent with previous findings that caffeine ingestion contributes to insulin resistance.     

Dietary serine and cystine attenuate the homocysteine-raising effect of dietary methionine: a randomized crossover trial in humans

BACKGROUND: A high plasma total homocysteine (tHcy) concentration is a risk factor for cardiovascular disease. The increase in tHcy induced by methionine, the sole dietary precursor of homocysteine, might be modulated by other amino acids present in dietary proteins. OBJECTIVES: Our objectives were to compare the postprandial effect of free and dietary methionine on plasma tHcy concentrations and to investigate whether serine and cystine modify the effect of free methionine on tHcy. DESIGN: We conducted a randomized crossover trial in 24 healthy men. Each subject ingested 4 meals on separate days, which were separated by 1 wk. tHcy concentrations were measured in the fasting state and at 2, 4, 6, 8, 10, and 24 h after meal ingestion. The meals were 1) a low-protein meal fortified with 30 mg methionine/kg body wt (reference, denoted by "Met"), 2) meal 1 additionally fortified with 60.6 mg serine/kg body wt (MetSer), 3) meal 1 additionally fortified with 12.3 mg cystine/kg body wt (MetCys), and 4) a protein-rich meal containing 30 mg methionine, 60.6 mg serine, and 12.3 mg cystine per kg body wt (Protein). RESULTS: The mean (+/-SD) fasting tHcy concentration was 9.1 +/- 2.7 micromol/L. Mean peak tHcy concentrations were 17.9 +/- 4.5, 14.3 +/- 3.3, 14.8 +/- 3.9, and 11.2 +/- 3.1 micromol/L after Met, MetSer, MetCys, and Protein, respectively. Compared with the mean 24-h area under the tHcy-by-time curve after Met, the mean curves after MetSer, MetCys, and Protein were 37%, 32%, and 77% smaller, respectively (all P < 0.0005). CONCLUSIONS: Dietary methionine increases tHcy much less than does free methionine. Serine and cystine attenuate the tHcy-raising effect of free methionine. Thus, dietary proteins with a high content of serine or cystine relative to methionine may lead to lower postprandial tHcy responses.     

Moderate exercise, postprandial energy expenditure, and substrate use in varying meals in lean and obese men

Maximizing postprandial energy expenditure and fat oxidation could be of clinical relevance for the treatment of obesity. This study investigated the effect of prior exercise on energy expenditure and substrate utilization after meals containing varying amounts of macronutrients. Eight lean (11.6%+/-4.0% body fat, M+/-SD) and 12 obese (35.9%+/-5.3% body fat) men were randomly assigned to a protein (43% protein, 30% carbohydrate) or a carbohydrate (10% protein, 63% carbohydrate) meal. The metabolic responses to the meals were investigated during 2 trials, when meals were ingested after a resting period (D) or cycling exercise (Ex+D; 65% of oxygen consumption reserve, 200 kcal). Energy expenditure, substrate utilization, and glucose and insulin responses were measured for 4 hr during the postprandial phase. Although postprandial energy expenditure was not affected by prior exercise, the total amount of fat oxidized was higher during Ex+D than during D (170.8+/-60.1 g vs. 137.8+/-50.8 g, p< .05), and, accordingly, the use of carbohydrate as substrate was decreased (136.4+/-45.2 g vs. 164.0+/-42.9 g, p< .05).After the protein meal fat-oxidation rates were higher than after carbohydrate intake (p< .05), an effect independent of prior exercise. Plasma insulin tended to be lower during Ex+D (p= .072) and after the protein meal (p= .066). No statistically significant change in postprandial blood glucose was induced by prior exercise. Exercising before meal consumption can result in a marked increase in fat oxidation, which is independent of the type of meal consumed.     

In vivo antioxidant effect of green tea

OBJECTIVE: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. DESIGN: We tested 10 healthy subjects (aged 23-25 y, five women and five men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80 degrees C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coefficient of variation was 1.2%. RESULTS: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not significant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a significant increase of 7.0% after 60 min and 6.2% after 120 min (P<0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P<0.0001). CONCLUSIONS: Total antioxidant capacity of plasma was significantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. SPONSORSHIP: This work was funded by the Pacific Corporation (Korea).