Influence of varying energy intake on nitrogen balance in men on two levels of protein intake.

Effect of changing energy levels of the diet at constant protein intakes on nitrogen balances in five young men were studied at two levels of protein--40 and 60 g. Nitrogen balance increased with increase in energy intake at both levels of protein. This was brought about primarily by a reduction in urinary nitrogen excretion. Energy levels at which nitrogen equilibrium was obtained were different for the two levels of protein intake. At 40 g protein intake the energy intake required for zero nitrogen balance was 2,249 kcal, while it was 2,066 kcal when the diet provided 60 g protein.     

The effect of low-carbohydrate diet on the pattern of hormonal changes during incremental, graded exercise in young men

The purpose of this study was to discover whether severe dietary carbohydrate (CHO) restriction modifies the relationship between exercise intensity and hormonal responses to exercise. Changes in the plasma adrenaline (A), noradrenaline (NA), growth hormone (hGH), testosterone (T), and blood lactate (LA) during an incremental exercise performed until volitional exhaustion were determined in 8 physically active volunteers after 3 days on low CHO (< 5% of energy content; L-CHO) and isocaloric mixed (M) diets. Following L-CHO diet, the basal plasma A, NA, and hGH concentrations were increased, whilst T and LA levels were decreased. During exercise all the hormones increased exponentially, with thresholds close to that of LA. Neither the magnitude nor the pattern of the hormonal changes were affected by L-CHO diet except the NA threshold, which was lowered. Blood LA response to exercise was diminished and LA threshold was shifted towards higher loads by L-CHO diet. It is concluded that restriction of CHO intake (a) does not affect the pattern of changes in plasma A, hGH, and T concentrations during graded exercise but lowers NA threshold, indicating increased sensitivity of the sympathetic nervous system to exercise stimulus; (b) alters the basal and exercise levels of circulating hormones, which may have an impact on the balance between anabolic and catabolic processes and subsequently influence the effectiveness of training.     

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.     

Urine nitrogen as an independent validatory measure of dietary intake: a study of nitrogen balance in individuals consuming their normal diet

In order to determine the value of 24 h urine nitrogen (N) excretion as a way of validating dietary methods of measuring protein intake in individuals, daily N intake and excretion has been measured in eight healthy subjects while consuming their usual, varying, diets for 28 days. Daily duplicates of all food eaten were obtained and consecutive 24 h collections of urine and feces were made throughout and analyzed for N by the Kjeldahl method. The completeness of the 24 h urine collections was verified by the use of PABA and of feces by radiopaque pellets. N losses in blood and from the skin were measured. The within person variation in dietary intake ranged from 14 to 26% (coefficient of variation, CV) while urine N was more constant, varying from 11 to 18% (CV) within individuals. In these subjects eight 24 h urine collections, verified for their completeness, were sufficient to estimate dietary N intake to within 81 +/- 5% (SD) as assessed by 18 day dietary records.     

The effect of exercise on food intake in men and women

To study the effect of acute exercise on caloric intake in normal-weight young people, food intake was monitored in 10 men and 10 women during consecutive 5-d periods, one with and one without exercise. Food intake during the exercise period was compared with that during the control period. Caloric intake during the control period was 2467 +/- 165 kcal/d (means +/- SEM) for men and 1831 +/- 103 kcal/d for women. During the exercise period the men increased their caloric intake to 2658 +/- 188 kcal/d and the women's caloric intake remained unchanged, 1830 +/- 91 kcal/d. Caloric intake was not affected by sequence of treatment or duration of protocol. Men responded to 5 d of acute exercise with increased caloric intake (208 +/- 64 kcal/d), which was insufficient to compensate for the caloric cost of exercise (596 kcal/d above resting metabolic rate). Women did not change their caloric intake despite expending 382 kcals/d during exercise. Consequently, both normal-weight men and women were in negative caloric balance during the exercise period.     

The effect of diet, exercise and 7,12-dimethylbenz(a)anthracene on food intake, body composition and carcass energy levels in virgin female BALB/c mice

This study investigated the effect of diet, exercise and , 7,12-dimethylbenz(a)anthracene (DMBA), a mammary-tumor carcinogen, on food intake, energy consumption, body weight and body composition in virgin female BALB/c mice. Interactions were examined among three diet conditions (standard AIN-76A, restricted AIN-76A and high fat AIN-76A diet), two exercise conditions (with and without treadmill exercise) and two treatment conditions (carcinogen or corn oil sham). Mice were randomized to one of 12 groups at 6 wk of age; beginning at 8 wk of age, all mice received either 7,12-dimethylbenz(a)anthracene (1 mg/0.2 mL corn oil) or 0.2 mL of corn oil via gastric tube once each week for six consecutive weeks. Exercise in a rotating-drum treadmill was initiated at 10 wk of age and was increased to a final rate of 6 m/min for 60 min, 5 d/wk. Mice were killed at 24 wk of age, confirmed to be tumor-free and analyzed for protein and fat content, from which body energy was calculated. Energy consumption was highest in the standard diet-fed groups followed by the high fat diet-fed groups and the restricted diet-fed groups. The groups fed the standard diet and restricted diet had similar body weight and carcass energy. Exercise or DMBA treatment generally reduced food consumption, energy intake, body weight and carcass energy. In summary, diet, exercise and DMBA all had pronounced effects on energy consumption, which in turn affected body composition. These treatments may influence expression of breast cancer via their effects on body composition.     

Residual effect of graded levels of exercise on metabolic rate

The hypothesis that exercise induces a residual effect on metabolic rate only when the intensity exceeds a certain threshold was tested by studying 10 healthy, untrained adults performing graded levels of bicycle ergometry on five separate occasions. The exercise consisted of four 30-min periods at intensities ranging from 0 to 100 Watts. Energy expenditure was measured by continuous indirect whole-body calorimetry. The highest level of exercise increased 24-h energy expenditure by 34 per cent. Food intake was modified for each measurement in order to maintain energy balance. Sleeping and basal metabolic rates on the night following exercise were raised even at low intensities of exercise. There was an almost linear dose-response relationship and no evidence of a threshold. However, the effect was small, amounting to only 5.8 per cent overnight and 3.9 per cent in the morning following 2 h exercise at over 60 per cent VO2 max during the preceding day. This suggests that the residual energy expenditure incurred after moderate levels of exercise is unlikely to be a very useful adjunct to slimming regimes.     

The effect of an incremental increase in exercise on appetite, eating behaviour and energy balance in lean men and women feeding ad libitum

The effects of incremental exercise on appetite, energy intake (EI), expenditure (EE) and balance (EB) in lean men and women were examined. Six men (age 29.7 (SD 5.9) years, weight 75.2 (SD 15.3) kg, height 1.75 (SD 0.11) m) and six women (age 24.7 (SD 5.9) years, weight 66.7 (SD 9.10) kg, height 1.70 (SD 0.09) m) were each studied three times during a 16 d protocol, corresponding to no additional exercise (Nex), moderate-intensity exercise (Mex; 1.5-2.0 MJ/d) and high-intensity exercise (Hex; 3.0-4.0 MJ/d) regimens. Subjects were fed to EB during days 1-2, and during days 3-16 they fed ad libitum from a medium-fat diet of constant composition. Daily EE, assessed using the doubly labelled water method, was 9.2, 11.6 and 13.7 MJ/d (P < 0.001; SED 0.45) for the women and 12.2, 14.0 and 16.7 MJ/d (P = 0.007; SED 1.11) for the men on the Nex, Mex and Hex treatments, respectively. EI was 8.3, 8.6 and 9.9 MJ/d (P = 0.118; SED 0.72) for the women and 10.6, 11.6 and 12.0 MJ/d (P = 0.031; SED 0.47) for the men, respectively. On average, subjects compensated for about 30 % of the exercise-induced energy deficit. However, the degree of compensation varied considerably among individuals. The present study captured the initial compensation in EI for exercise-induced energy deficits. Total compensation would take a matter of weeks.     

Relationship between protein intake and nitrogen balance in obese patients on low energy diet

The effect of nitrogen intake on nitrogen balance was studied in six obese patients receiving low energy diets. They were given a control diet containing 2,000 kcal of energy and 80 g of protein for the first ten days. Then they were given Diet A with 1,100 kcal of energy and 70 g of protein for the next 2 weeks, followed by Diet B with 1,100 kcal of energy and 50 g of protein for 2 weeks. The relationship between nitrogen intake (X, mg/kg) and nitrogen balance (Y, mg/kg) during the low energy diet periods was statistically significant, with Y = 0.388X-60.32 (SD = 17.71, r = +0.67, n = 11, p less than 0.05). The nitrogen and protein requirements were estimated from this equation to be 201.1 mg/kg and 1.26 g/kg, respectively. In our experiment, the nitrogen balance in obese patients was well maintained although total energy was reduced to 1,100 kcal/day in Diet A. It is suggested that protein quantity in the diets should be taken into account when a low energy diet is used for the treatment of obesity.     

Eating frequency and energy regulation in free-living adults consuming self-selected diets

The relative importance of eating frequency to weight control is poorly understood. This review examines the evidence to date on the role of eating frequency in weight control in free-living adults. The majority of cross-sectional studies in free-living adults show an inverse relationship between eating frequency and adiposity; however, this is likely an artifact produced by the underreporting of eating frequency concurrent with underreporting of energy intake. When implausible energy intake reporting (which is mostly underreporting) is taken into account, the association between eating frequency and adiposity becomes positive. In studies in which eating frequency is prescribed and food intake is mostly self-selected, there is either no effect or a minor positive effect of eating frequency on energy intake. Most of those studies have been short-term and lack the necessary dietary biomarkers to validate reported energy intakes and eating frequencies. In conclusion, there is some suggestion from cross-sectional studies in which energy intake underreporting is taken into account and from experimental studies to date that greater eating frequency may promote positive energy balance. However, experimental studies of longer-term duration that include objective dietary biomarkers are necessary before firm conclusions about the relative importance of eating frequency in weight control can be made.     

Metabolic balance of manganese in young men consuming diets containing five levels of dietary manganese

Five healthy men, ages 19-20, were fed a diet for 105 d to measure manganese balance during consumption of conventional foods. The study was divided into five periods of 21, 21, 38, 11 and 14 d, in which the daily dietary intakes of manganese (Mn) were 2.89, 2.06, 1.21, 3.79 and 2.65 mg, respectively. During the last 7 d of each dietary period, subjects resided in a metabolic unit and fasting blood samples were drawn on two mornings. Feces and urine were collected during the last 6 d and integumental losses were collected during the last 60 h of each period. The mean Mn balances for periods 1-5 were -0.083, -0.018, -0.088, +0.657 and +0.136 mg/d, respectively. Corresponding apparent retentions were -2.90, -0.88, -7.40, +17.33 and +5.12%. The mean sum of endogenous and exogenous losses when intake was theoretically zero was calculated to be 392 micrograms/d. When these total losses were combined with the mean positive retention, the theoretical mean dietary level of Mn required for positive balance for these male subjects was 3.5 mg/d or 50 micrograms/kg.     

Diet composition, energy intake, and exercise in relation to body fat in men and women

This study examined the relationships among body fat, diet composition, energy intake, and exercise in adults. Male (n = 107) and female (n = 109) adults aged 18-71 y (36.6 +/- 1.0 y, means +/- SEM) were hydrostatically weighed to determine body fat (5.7-49.0% of total weight). Diet and exercise behaviors were determined by use of a questionnaire. As body fat increased, percent of energy intake derived from fat increased (p less than 0.001) whereas the percent from carbohydrate decreased (p less than 0.001). There was no relationship between energy intake and adiposity although leanness and exercise were related (p less than 0.001). When subgroups of lean and obese subjects were compared, the lean subjects derived approximately 29% of their energy from fat and 53% from carbohydrate vs 35% and 46%, respectively, for the obese subjects. No differences were found between groups for energy intake but the lean individuals exercised more often than did the obese individuals. These data suggest that diet composition may play as important a role in fat deposition as do energy intake and lack of exercise.     

Sodium and potassium intake and balance in adults consuming self-selected diets

Twenty eight adults, 12 men and 16 women, participated in a 1-yr study designed to assess daily nutrient intake accurately. All subjects lived at home, consumed self-chosen diets, and maintained a detailed daily dietary record throughout the year. During four 7-day balance studies, one in each season of the year, meals, beverages, urine, and feces were analyzed for sodium and potassium content by atomic absorption spectrometry. Total intakes averaged 3.4 g/day for sodium and 2.8 g/day for potassium. The Na:K ratio for all diets analyzed averaged 1.3. Nutrient densities of sodium and potassium were 1.8 and 1.5 g/1000 kcal, respectively. Apparent absorptions of sodium and potassium were 98 and 85%, respectively, and did not change significantly over the wide range of intakes. Average urinary excretions of sodium and potassium were 86 and 77% of total intake, respectively. Mean metabolic balances were positive for sodium, +0.47 g/day, and potassium, +0.28 g/day. The data of this study provide useful information concerning the dietary intakes, excretions, and balances of sodium and potassium for adults based on analytic determination.     

Effect of moderate intensity exercise on acute energy intake in normal and overweight females

The purpose of this study is to determine the impact of moderate intensity exercise on acute post-exercise energy intake (EI) in normal and overweight females. Twelve normal weight (BMI<25), and 12 over weight (BMI>25) inactive women (mean age 35+/-8) participated in a 2-day experimental study. On the exercise day, participants were asked to walk on a treadmill at 60% maximum heart rate for 1h. After the exercise, participants selected and ate food at a university cafeteria. Post-exercise EI was compared to a non-exercise day. A single mixed model repeated 2 x 2 ANOVA was used to determine the impact of exercise on post-exercise EI. The overweight women consumed significantly more (p<0.02) than the normal weight women on both experimental days and there was a significant (p<0.03) difference in fat intake. The higher post -exercise EI of the overweight group may have been due to the energy needs associated with a higher BMI but it is also possible that cognitive factors, food availability and environment may influence post-exercise EI.     

Comparison of energy and protein intakes of older people consuming a texture modified diet with a normal hospital diet

BACKGROUND: There are very few studies looking at the energy and protein requirements of patients requiring texture modified diets. Dysphagia is the main indication for people to be recommended texture-modified diets. Older people post-stroke are the key group in the hospital setting who consume this type of diet. The diets can be of several consistencies ranging from pureed to soft textures. OBJECTIVE: To compare the 24-hour dietary intake of older people consuming a texture modified diet in a clinical setting to older people consuming a normal hospital diet. METHOD: Weighed food intakes and food record charts were used to quantify the patients' intakes, which were compared to their individual requirements. RESULTS: The oral intake of 55 patients was measured. Twenty-five of the patients surveyed were eating a normal diet and acted as controls for 30 patients who were prescribed a texture-modified diet. The results showed that the texture-modified group had significantly lower intakes of energy (3877 versus 6115 kJ, P < 0.0001) and protein (40 versus 60 g, P < 0.003) compared to consumption of the normal diet. The energy and protein deficit from estimated requirements was significantly greater in the texture-modified group (2549 versus 357 kJ, P < 0.0001; 6 versus 22 g, P = 0.013; respectively). CONCLUSION: These statistically significant results indicate that older people on texture-modified diets have a lower intake of energy and protein than those consuming a normal hospital diet and it is likely that other nutrients will be inadequate. All patients on texture-modified diets should be assessed by the dietitian for nutritional support. Evidence based strategies for improving overall nutrient intake should be identified.     

饮食指导对妊娠期糖代谢异常孕妇血脂水平的影响

目的:研究饮食指导对妊娠期糖尿病(GDM)及妊娠期糖耐量低减(G IGT)的妊娠女性孕期血脂水平的影响。方法:将2001年1月~2002年1月在北京妇产医院定期进行产前检查并分娩的113例妊娠女性分为3组:正常妊娠组64例,GDM组22例及G IGT组27例。3组分别于孕早中期(28周前)、孕晚期(32~42周)及哺乳期(产后2月)测定母亲的血脂水平,对所有指标进行秩和检验、单因素方差分析及两两比较。结果:随着妊娠的进展,各组的血脂水平均有所增加,经统计学检验,均有显著性差异,但GDM、GIGT和正常妊娠组之间的血脂水平在各阶段并无显著性差异。结论:高脂血症是妊娠期脂类代谢的特点之一。在糖代谢异常的患者中,由于胰岛素(INS)相对不足或缺乏,患GDM及G IGT的妊娠女性其脂代谢紊乱本应进一步加重,但经积极的饮食指导可延缓脂代谢紊乱的发生。