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PubMed1995

Differential effect of age on metabolisable energy content of high protein-low energy and low protein-high energy diets in young broiler chicks.

1. An experiment was carried out with 6-d old male broiler chicks in an attempt to understand better the effect of age on dietary AMEn of high protein-low energy (HPLE) and low protein-high energy (LPHE) diets which are used in the determination of the AMEn content of grains when substituted for the entire diet. The experiment was carried out in a split-plot design in which the effects of 2 diets (HPLE-reference and LPHE-test, containing maize) on food intake, faecal excretion, dietary AMEn and the utilisation of the nutrients were evaluated in 3 age periods (A = 11-13, B = 15-17 and C = 20-22 d of age). 2. Chicks fed on the HPLE diet consumed significantly less food than those fed on the LPHE diet during periods A and B, but not in C. They also produced a significantly larger amount of droppings during periods B and C. Food-to-droppings ratio, which was consistently and significantly lower in chicks fed on the HPLE diet, decreased markedly in period C only in these birds. 3. Absolute and relative retention (RR) of dry matter (DM) and starch, and RR of nitrogen (N) from birds fed on the HPLE diet, were consistently and significantly lower than from those fed on the LPHE diet, but fat retention (absolute and relative) was higher. RR of DM and of N in period C was significantly lower than in periods A and B, while RR of fat and of starch was not affected by age. The effect of age on RR of N was observed only with the HPLE diet. 4. AMEn of the HPLE diet, but not of the LPHE diet, in period C was significantly lower than in periods A and B, resulting in a significant interaction between age and diet and a general reduction with age. The calculated AMEn contents of the maize in periods A and B were essentially the same (14.91 and 14.85 MJ/kg, respectively), and lower than in period C (15.28 MJ/kg). It is concluded, therefore, that because of its effect on AMEn of the HPLE reference diet in chicks older than 17 d, bird age is of considerable importance in the determination of AMEn in grains when substituted for the entire diet.

Aging↗
PubMed1990

The defibrillation success rate versus energy relationship: Part I--Curve fitting and the most efficient defibrillation energy.

The effect of applying an energy pulse to the heart during ventricular fibrillation is described by the probability of successful defibrillation or success rate. Seven to ten (8.60 +/- 0.84: mean +/- standard deviation) defibrillation trials per energy were randomly attempted at energies which span the defibrillation success rate versus energy curve. We obtained 70.0 +/- 8.4 episodes per dog. We fit the defibrillation success rate versus energy relationship from ten dogs (20.5 +/- 1.5 kg) to four types of curves: linear, exponential, probit transformed linear, and logit transformed linear. The correlation coefficients for each fit are 0.917 +/- 0.057, 0.944 +/- 0.014, 0.926 +/- 0.51, and 0.889 +/- 0.098, respectively. We therefore conclude that the exponential curve best describes the DSRE relationship. This suggests the existence of an energy below which defibrillation does not occur. At higher energies, the exponential curve asymptotically approaches a 100% success rate, which indicates that increasing the energy produces a diminishing benefit to defibrillation success rate. The estimated energies with a 0% defibrillation success rate are surprisingly consistent among dogs, with 2.072 +/- 0.553 J. The estimated energy with an 80% defibrillation success rate is 5.217 +/- 1.091 J. The estimated defibrillation success rate corresponding to the defibrillation threshold of 3.59 +/- 1.06 J is consistent with 0.516 +/- 0.144. The estimated energies with a 0% success rate correlate well with the defibrillation thresholds with R = 0.772; P = 0.0088. Since implantable defibrillators have a limited energy supply, we determined energy efficiency by dividing defibrillation success rate by the applied energy and energy consumption by dividing the applied energy by the defibrillation success rate. The most efficient defibrillation energy occurs at the maximum energy efficiency and the minimum energy consumption. The most efficient defibrillation energy of 4.34 +/- 0.97 J determined from the exponential fit has a success rate of 0.70 +/- 0.06. The most efficient defibrillation energy can be predicted from the defibrillation threshold. Clinically, a 70% success rate may not be adequate. We, therefore, compared the energy efficiency and consumption of energies with 90% and 95% success rates to the most efficient defibrillation energy. About a 50% increase in energy from the most efficient defibrillation energy is necessary for a 90% success rate which results in about a 13% loss in energy efficiency and about a 16% increase in energy consumption. About an 84% energy increase is necessary for a 95% success rate which results in about a 24% loss in energy efficiency and about a 33% increase in energy consumption.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

A twin study of the effects of energy density and palatability on energy intake of individual foods.

The relative effects of energy density and palatability on energy intake, and whether there are familial influences on these effects, are not known. We investigated this issue in 7 pairs of healthy, male monozygotic twins (mean+/-SD age 26.3+/-8.6 years, BMI 23.7+/-3.2 kg/m(2)) in a clinical study involving covert ad libitum feeding of high-fat (HF, approximately 40%) and low-fat (LF, approximately 20%) diets in two 9-day phases. Diets were matched for average energy density, protein, fiber, and initial reported taste pleasantness, but these factors varied among the individual foods. Relationships between energy density, palatability, and energy intake were explored using regression and path analyses. Food energy density was positively associated with average taste pleasantness (r=0.46, P=0.03) independent of fat content, while energy intake from individual foods was positively associated with both energy density (r=0.56, P=0.007) and taste pleasantness (r=0.73, P<0.0001). In path analysis, both energy density and taste pleasantness directly influenced energy intake, and energy density also indirectly influenced energy intake by influencing taste pleasantness. In addition, there were significant within-twin pair similarities for the energy density-taste pleasantness and energy density-energy intake relationships (P<0.03) with the result that some twin pairs but not others identified foods high in energy density as more pleasant tasting and consumed relatively more energy from them compared to foods low in energy density. These results suggest that there are familial influences on the extent to which high energy density foods are preferred and contribute to total energy intake.

Adult↗
PubMed2003

Subthreshold test pulses versus low energy shock delivery to estimate high energy lead impedance in implanted cardioverter defibrillator patients.

The high energy lead impedance is valuable for detecting lead failure in ICDs, but until recently shock delivery was necessary for high energy impedance measurement. This study compared the use of subthreshold test pulses and low energy test shocks to estimate the high energy impedance. Immediately after implantation of Ventak Prizm ICDs in 29 patients, the lead impedance was measured with five subthreshold (0.4 microJ) test pulses, 5 low energy (1.1 J) shocks, and two to three high energy (16 +/- 4.5 J) shocks. The mean impedances measured using high energy shocks, low energy shocks, and subthreshold pulses were 42.0 +/- 7.3 omega, 46.5 +/- 8.1 omega, and 42.4 +/- 7.1 omega, respectively. The impedances measured using high and low energy shocks differed significantly (P < 0.0001), while those obtained by high energy shocks and low energy pulses did not (P = 0.63). According to the Pearson correlation coefficient, the impedance measurements with subthreshold pulses and low energy shocks were both closely correlated (P < 0.0001) with impedance values determined with high energy shocks. However, while the impedance values tended to be higher when measured with low energy shocks, the concordance correlation coefficient (c) was higher for subthreshold test pulse versus high energy shock (c = 0.92) than for low versus high energy shock (c = 0.73). Furthermore, the intraindividual variability of impedance measurements was lower with subthreshold pulse measurements than with low energy shocks. Compared with low energy shocks, impedance measurement with subthreshold pulses has higher reproducibility and a higher correlation with the impedance obtained by high energy shock delivery. Safe and painless high energy impedance estimation with subthreshold pulses might, therefore, help to detect ICD lead failure during routine follow-up.

Aged↗
PubMed1996

Effects of energy imbalance on energy expenditure and respiratory quotient in young and older men: a summary of data from two metabolic studies.

The roles of energy expenditure and substrate oxidation in energy regulation, and the effects of factors such as aging on these parameters, remain uncertain. A re-analysis of data from two studies involving overfeeding or underfeeding in young men (22.7 +/- 0.6 [SEM] years) and older men (68.0 +/- 1.50 years) was conducted to further evaluate the adaptive capacity of energy expenditure and respiratory quotient to an increase or a decrease in energy intake. Changes in total energy expenditure (TEE) and resting energy expenditure (REE) and respiratory quotient (RQ) in response to energy imbalance were compared between subjects undergoing overfeeding by 4.1 MJ/day for 21 days, or underfeeding by 3.2 MJ/day for 21 days. Comparing responses to overfeeding or underfeeding, there was a significant TEE response to energy imbalance averaging 1.39 MJ/day and equivalent to 19% of the alteration in energy intake (p < 0.05). There was also a significant REE response to energy imbalance averaging 0.45 MJ/day (p < 0.001), and a significant RQ response in both fasting and fed states (p < 0.01). There was no significant difference between young and older men in their TEE, energy deposition or RQ responses to energy imbalance, but older men did have significantly diminished REE response to energy imbalance (p < 0.05) and a significantly delayed thermic response to a standard meal (p < 0.05). These data indicate that energy expenditure plays a significant role in attenuating the effects of alterations in energy intake on body energy stores and that, based on some measures of energy expenditure, aging is associated with a reduction in the adaptive capacity of energy expenditure to participate in energy regulation.

Adult↗
PubMed2001

Energy density of foods affects energy intake across multiple levels of fat content in lean and obese women.

BACKGROUND: The results of previous studies indicated that energy density, independent of fat content, influences energy intake. In most studies, however, both fat content and energy density were lower than in typical American diets. OBJECTIVE: We examined the influence of energy density on intake when fat content was above, below, or similar to the amount of fat typically consumed and when energy density was closer to that of American diets. DESIGN: Lean (n = 19) and obese (n = 17) women consumed all meals daily in our laboratory during 6 experimental sessions. The main entrées, consumed ad libitum, were formulated to vary in fat content (25%, 35%, and 45% of energy) and energy density (5.23 kJ/g, or low energy density, and 7.32 kJ/g, or high energy density) but to have similar palatability. RESULTS: Energy density influenced energy intake across all fat contents in both lean and obese women (P < 0.0001). Women consumed less energy in the low (7531 kJ) than in the high (9414 kJ) energy density condition. Despite this 20% lower energy intake, there were only small differences in hunger (7%) and fullness (5%). Women consumed a similar volume, but not weight, of food daily across conditions. Differences in intake by weight, but not volume, occurred because for some versions of manipulated foods, weight and volume were not directly proportional. CONCLUSIONS: Energy density affected energy intake across different fat contents and at levels of energy density comparable with those in typical diets. Furthermore, our findings suggest that cues related to the amount of food consumed have a greater influence on short-term intake than does the amount of energy consumed.

Adult↗
PubMed2006

Dietary energy density is associated with energy intake and weight status in US adults.

BACKGROUND: Laboratory-based investigations indicate that the consumption of foods with a low energy density (kcal/g) decreases energy intake. Although low-energy-dense diets are recommended for weight management, relations between energy density, energy intake, and weight status have not been clearly shown in free-living persons. OBJECTIVES: A representative US sample was used to determine whether dietary energy density is associated with energy intake, the weight of food consumed, and body weight and to explore the influence of food choices (fruit, vegetable, and fat consumption) on energy density and body weight. DESIGN: A cross-sectional survey of adults (n = 7356) from the 1994-1996 Continuing Survey of Food Intakes by Individuals and two 24-h dietary recalls were used. RESULTS: Men and women with a low-energy-dense diet had lower energy intakes (approximately 425 and 275 kcal/d less, respectively) than did those with a high-energy-dense diet, even though they consumed more food (approximately 400 and 300 g/d more, respectively). Normal-weight persons had diets with a lower energy density than did obese persons. Persons with a high fruit and vegetable intake had the lowest energy density values and the lowest obesity prevalence. CONCLUSIONS: Adults consuming a low-energy-dense diet are likely to consume more food (by weight) but to have a lower energy intake than do those consuming a higher-energy-dense diet. The energy density of a variety of dietary patterns, including higher-fat diets, can be lowered by adding fruit and vegetables. Our findings support the hypothesis that a relation exists between the consumption of an energy-dense diet and obesity and provide evidence of the importance of fruit and vegetable consumption for weight management.

Adult↗
PubMed1994

Effects of increased energy intake and/or physical activity on energy expenditure in young healthy men.

This study was designed to examine effects of alterations in energy balance on adaptive changes in components of total energy expenditure (TEE). Nineteen young healthy males were studied during a 10-day sedentary energy balance baseline period and then randomly assigned to one of four 10-day treatment groups: 1) no change in energy intake (EI) or physical activity (PA; energy balance at low energy flux), 2) EI increased by 50% with no change in PA (positive energy balance), 3) TEE increased by 50% by increasing PA, matched by a 50% increase in EI (energy balance at high energy flux), and 4) TEE increased by 50% by increasing PA with no change in EI (negative energy balance). TEE was measured with doubly labeled water, resting metabolic rate (RMR) by indirect calorimetry, and thermic response to feeding (TEF) by indirect calorimetry; energy expenditure of physical activity (EEPA) was estimated by subtracting RMR, TEF, and prescribed PA from TEE. TEE was significantly increased by PA (by design) but not EI. There was a significant main effect of intake and a significant intake-by-activity interaction for changes in RMR. In post hoc analysis, RMR was significantly increased during positive energy balance and energy balance at high energy flux relative to change in RMR when energy balance was maintained at low energy flux. A significant increase in RMR was also noted during negative energy balance after adjustment for change in fat-free mass. There was no significant difference in change in RMR among the three treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Diet energy density and energy intake in palliative care cancer patients.

BACKGROUND & AIMS: Anorexia and cachexia are frequent in advanced cancer. Energy density may be important in the control of energy intake; however, current data are derived from studies in healthy or obese populations and there is no agreed definition and methods of calculation. We studied energy density and energy intake in a group of palliative cancer patients and explored which method of energy density calculation that yielded the highest determination coefficient of energy intake. METHODS: Energy density was calculated from 259 food records using four methods, differing in the types of food and beverages included in the analysis. Association between energy density and energy intake was tested using regression analysis. RESULTS: The determination coefficient for total energy intake was: 0.181, 0.148, 0.222, and 0.211 for methods 1-4, respectively (P for all <0.001). In relation to energy per kg body weight and resting energy expenditure, methods 3 and 1 yielded the highest determination coefficient, R2 = 0.164 and 0.184, respectively. CONCLUSIONS: We found a positive association between diet energy density and energy intake. The method used when calculating energy density had limited impact on this association. When calculating energy density all food and beverages should be included in the analysis.

Adult↗
PubMed1980

Energy balance and metabolic rate in preterm infants fed with standard and high-energy formulas.

1. Energy balances were performed on sixteen low birth weight preterm infants over 7-10 d periods on a standard low-solute infant formula (2600 kJ/l), and on four high-energy formulas, providing different energy densities up to 3760 kJ/l. In two of the high-energy formulas the additional fat energy was provided by peanut oil, and the other two by medium chain triglycerides (MCT). Anthropometric measurements and metabolic rate (MR) determinations were made during the balance periods. 2. Mean energy retention on the standard formula was 66% of the intake and declined to below 50% on the two feeds providing the highest energy. Extensive energy balance data on the standard formula are available for reference. 3. Net absorption of dietary energy increased on all the high-energy formulas, rising from 362 kJ/kg per d on the standard formula to 453 kJ/kg per d on the highest energy-formula (P < 0.001). There was no advantage in using MCT. 4. Net absorption of dietary energy improved with advancing maturity, irrespective of the formula. 5. In spite of the increased dietary energy retention, there was no increase in growth rate during periods of feeding with the high-energy formulas. 6. Fasting and postprandial MR increased by 10.4 and 12.8% respectively on the highest energy feeds. 7. It is concluded that, at least in the short term, this type of high-energy feeding increases MR at the expense of growth and thus is probably of no advantage to the infant.

Blood Physiological Phenomena↗
PubMed2006

Reductions in portion size and energy density of foods are additive and lead to sustained decreases in energy intake.

BACKGROUND: When the portion size and energy density (in kcal/g) of a food are varied simultaneously in a single meal, each influences energy intake independently. OBJECTIVE: We aimed to determine how the effects of portion size and energy density combine to influence energy intake and satiety over multiple meals for 2 d. DESIGN: In a crossover design, 24 young women were provided with meals and snacks for 2 consecutive days per week for 4 wk; all foods were consumed ad libitum. Across the 4 sessions, the subjects were served the same 2 daily menus, but all foods were varied in portion size and energy density between a standard level (100%) and a reduced level (75%). RESULTS: Reducing the portion size and energy density of all foods led to significant and independent decreases in energy intake over 2 d (P < 0.0001). A 25% decrease in portion size led to a 10% decrease in energy intake (231 kcal/d), and a 25% decrease in energy density led to a 24% decrease in energy intake (575 kcal/d). The effects on energy intake were additive and were sustained from meal to meal. Despite the large variation in energy intake, there were no significant differences in the ratings of hunger and fullness across conditions over the 2 d. CONCLUSIONS: Reductions in portion size and energy density independently decreased ad libitum energy intake in women when commonly consumed foods were served over 2 d. Reductions in both portion size and energy density can help to moderate energy intake without increased hunger.

Adult↗
PubMed2004

Energy value of pig feeds: effect of pig body weight and energy evaluation system.

Ad libitum energy intake and performance in pigs depends on many animal and environmental factors in which feed energy density plays an important role. In addition, feed represents an important cost in pig production, and energy represents the greatest proportion of this cost. It is therefore important to express the feed energy value on an appropriate basis, and both energy supply (a dietary characteristic) and energy requirement (an animal characteristic) should be expressed using the same system. Energy content depends first on the nutrient composition; the constituents differ markedly in GE content (23.0, 39.0, 17.4, and 18.4 kJ/g for CP, fat, starch, and dietary fiber, respectively). Due to differences in digestibility and associated endogenous energy losses, the actual contribution of nutrients to apparent DE supply in growing pigs is even more variable and ranges from 31.7 kJ/g for fat, 22.4 kJ/g for CP, 17.2 kJ/g for starch, to only 3.2 kJ/g for dietary fiber. Nutrient composition also affects the efficiency of conversion of ME to NE, which varies from 90% for fat to 82% for starch and 60% for CP. Consequently, the energy values (relative to a conventional diet containing 14.2, 13.6, and 10.3 MJ/kg of DE, ME, and NE, respectively) of corn, soybean meal, and animal fat are 100, 104, and 235 on a DE basis; 102, 99, and 244 on a ME basis; and 107, 79, and 289 on a NE basis. Energy value thus depends on the system of evaluation. The energy density of pig feeds can also be affected by feed processing. For example, pelleting markedly increases fat and energy digestibilities in corn or full-fat rapeseed. Also the animal itself can affect the energy value of nutrients; digestion of dietary fiber becomes more efficient with increasing BW, with subsequent differences in energy content of feeds according to BW. In conclusion, a satisfactory characterization of the energy value of feeds should be based on their NE content. Factors affecting nutrients digestibility (e.g., BW and feed processing) should also be taken into account.

Animal Feed↗
PubMed2001

Energy density, energy intake and weight status in a large free-living sample of Chinese adults: exploring the underlying roles of fat, protein, carbohydrate, fiber and water intakes.

OBJECTIVE: This paper uses observational data to explore what dietary constituents might be responsible for associations between energy density, energy intake and weight status among free-living individuals. DESIGN: Cross-sectional data on 5783 Chinese adults (aged 20-59 y) from the 1991 China Health and Nutrition Surveys were used to test for associations between energy density, energy intake and weight status, controlling for age, sex, height, activity level, smoking status, urban residence and income. Pearson correlation coefficients were calculated to identify nutrient intake correlates of energy density. Replacing energy density with its nutrient correlates (3 day mean estimates of fat, protein, fiber and water intakes) in the models predicting energy intake and overweight status, the independent effects of specific nutrients were investigated. RESULTS: Energy density was positively and significantly associated with energy intake and overweight status. Energy density was significantly correlated with every nutrient examined, although the correlations were weak for most variables except water intake. Only water intake behaved consistently across analyses. It was negatively correlated with energy density, negatively, significantly and independently associated with energy intake as well as overweight status. Despite positive associations with energy intake, fat and protein intake were not significant predictors of overweight status. Fiber intake was strongly and positively associated with overweight status. CONCLUSIONS: Of the nutrients examined, only water intake appeared to explain the effects of energy density on energy intake and overweight status.

Adult↗
PubMed2002

Thermogenesis associated with fermentable carbohydrate in humans, validity of indirect calorimetry, and implications of dietary thermogenesis for energy requirements, food energy and body weight.

BACKGROUND: Animal studies and theory show fermentable carbohydrate (FC) intake causes appreciably thermogenesis, but a similar occurrence in humans is controversial. HYPOTHESES: (a) That indirect calorimetry (IDC) is a valid method to assess thermogenesis during fermentation. (b) That a consistent and rigorous approach to the analysis of published IDC data from human studies will establish a representative thermogenic response to FC. (c) That conventional estimates of food energy and energy requirements can mismatch appreciably, more especially when thermogenesis is ignored. PURPOSE: To derive information and understanding of IDC, thermogenesis and energy balance in relation to food energy and energy requirement estimates. METHODS: (a) The validities of IDC equations that estimate the heat of reaction and carbohydrate utilization were assessed for various types of FCs under various circumstances. (b) Pooled analysis of eight published randomized cross-over studies in humans with elevation of FC intake. Studies were analysed for the first time or reanalysed according to a consistent approach with appropriate corrections for confounders. (c) Some 1500 regular and 'special' diet compositions were examined to assess the extent to which Atwater general food energy factors and updated estimates of energy requirements mismatch due to variation in substrate-associated thermogenesis and substrate-associated faecal+urinary energy losses. Impact of such mismatches on BMI was assessed under conditions of all else being equal. RESULTS: (a) Indirect calorimetry was valid, providing robust estimates of heat production during various types of fermentation; only small correction factors were necessary. By contrast, IDC equations for carbohydrate utilization sometimes applied poorly to FC. (b) A best estimate of thermogenesis in humans due to fermentation, above that due to oral glucose as a reference standard, was 0.39 (s.e.m. 0.14) kJ per kJ net metabolizable energy (NME; P<0.05, n=8 studies, total 72 humans) compared with 0.34 kJ/kJ from theory. Six sources of bias were identified; all had potential to underestimate FC thermogenesis. (c) Mismatches in energy availability and requirement estimates were often marked and translated into long-term differences in body mass index from approximately 20 to 33 kg/m(2) in average-height middle-aged initially obese women, and from approximately 22 to a non-survivable 13 kg/m(2) in initially slim women. CONCLUSIONS: (a) Indirect calorimetry is valid for the present purpose. (b) Thermogenesis in response to FC is real in humans and is comparable to that in animals and in theory. (c) Mismatches between estimates of energy requirements and dietary energy as metabolizable energy means the two expressions are not directly comparable, which has implications for the expression of food energy, energy requirements and the conduct and interpretation of research related to body weight.

Body Weight↗
PubMed1984

Quantification of energy consumption in platelets during thrombin-induced aggregation and secretion. Tight coupling between platelet responses and the increment in energy consumption.

The involvement of metabolic energy in platelet responses was investigated by measuring the energy consumption during aggregation and secretion from dense, alpha- and acid-hydrolase-containing granules. Gel-filtered human platelets were stimulated with different amounts of thrombin (0.05-5.0 units X ml-1). At various stages during aggregation and secretion the energy consumption was measured from the changes in metabolic ATP and ADP following abrupt arrest of ATP resynthesis. Stimulation with 5 units of thrombin X ml-1 increased the energy consumption from 6.2 +/- 0.9 to 17.8 +/- 0.4 mumol of ATPeq. X min-1 X (10(11) platelets)-1 during the first 15 s. It decreased thereafter and returned to values found in resting cells after about 30 s. With 0.05 unit of thrombin X ml-1, the energy consumption accelerated more slowly and took at least 3 min before it normalized. A strong positive correlation was found between the velocities of the three secretion responses and the concurrent energy consumption (a) at different stages of the responses induced by a given dose of thrombin, and (b) at different secretion velocities initiated by different amounts of thrombin. When, at different stages of the responses, the extent of secretion was compared with the amount of energy that had been consumed, a strong linear correlation was found with the increment in energy consumption but not with the total energy consumption. This correlation was independent of the concentration of thrombin and indicated that complete secretion from dense, alpha- and acid-hydrolase-containing granules was paralleled by an increment of 4.0, 6.5 and 6.7 mumol of ATPeq. X (10(11) platelets)-1, respectively. An energy cost of 0.7 mumol of ATPeq. X (10(11) platelets)-1 was calculated for separate dense-granule secretion, whereas the combined alpha- and acid-hydrolase granule secretion required 5.3 mumol of ATPeq. X (10(11) platelets)-1. There was no correlation between energy consumption and optical aggregation. In contrast, the rate of single platelet disappearance, which is a measure for the early formation of small aggregates, correlated closely with the rate of energy consumption. Compared with secretion, however, the energy requirement of single platelet disappearance was minor, since 2mM-EDTA completely prevented this response but decreased the energy consumption only slightly. An increase of 0.5-1.0 mumol of ATPeq. X (10(11) platelets)-1 was seen before single platelet disappearance and the three secretion responses were initiated, indicating an increase in energy consuming processes that preceded these responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylglucosaminidase↗
PubMed2004

Combined effects of energy density and portion size on energy intake in women.

BACKGROUND: Increases in both the portion size and energy density of food have both been shown to increase energy intake, but the combined effects of such increases have not been investigated. OBJECTIVE: The objective was to determine the combined effects of energy density and portion size on energy intake in women. DESIGN: This study used a within-subjects design. Once a week for 6 wk, 39 women were served breakfast, lunch, and dinner ad libitum. The main entrée at lunch was formulated in 2 versions that varied in energy density (5.23 or 7.32 kJ/g), each of which was served in 3 different portion sizes (500, 700, or 900 g). The 2 versions were matched for macronutrient composition and palatability. Breakfast and dinner were standard meals. RESULTS: Increases in portion size and energy density led to independent and additive increases in energy intake (P <0.0001). Subjects consumed 56% more energy (925 kJ) when served the largest portion of the higher energy-dense entrée than when served the smallest portion of the lower energy-dense entrée. Subjects did not compensate for the additional intake by eating less at the subsequent meal. Despite substantial differences in energy intake, no systematic differences in ratings of hunger and fullness across conditions were observed. CONCLUSIONS: The energy density and the portion size of a food act independently to affect energy intake. The findings indicate that large portions of foods with a high energy density may facilitate the overconsumption of energy.

Adult↗
PubMed1994

Mechanical energy management in cycling: source relations and energy expenditure.

Conservation of energy suggests that during cycling the constrained lower extremity is capable of delivering energy to the bicycle without expending energy to move the limbs. The purpose of this study was to characterize the management of mechanical energy during cycling and, specifically, to evaluate the potential for system energetic conservatism. Mechanical energy contributions derived from lower extremity energy sources were computed for 12 experienced male cyclists riding at five combinations of cadence and power output. The knee joint dominated (> 50%) in contributing to system energy and a moderate amount of energy was derived from hip joint reaction forces (> 6%). Energy generations and dissipations at the sources were sensitive to power output and, within the range of conditions studied, insensitive to cadence. Two energy models estimated mechanical energy expenditure under hypothetical single-joint and multijoint muscle operating conditions. When multijoint muscles were incorporated into the energy management analysis, a significant reduction in mechanical work relative to the single-joint muscle operation occurred. Energy savings associated with multijoint muscle energy transfers were enhanced at higher bicycle power levels, suggesting that conservation of mechanical energy is plausible given appropriate actions of two-joint muscles.

Adolescent↗
PubMed2002

A method for optimizing potential-energy functions by a hierarchical design of the potential-energy landscape: application to the UNRES force field.

A method for optimizing potential-energy functions of proteins is proposed. The method assumes a hierarchical structure of the energy landscape, which means that the energy decreases as the number of native-like elements in a structure increases, being lowest for structures from the native family and highest for structures with no native-like element. A level of the hierarchy is defined as a family of structures with the same number of native-like elements (or degree of native likeness). Optimization of a potential-energy function is aimed at achieving such a hierarchical structure of the energy landscape by forcing appropriate free-energy gaps between hierarchy levels to place their energies in ascending order. This procedure is different from methods developed thus far, in which the energy gap and/or the Z score between the native structure and all non-native structures are maximized, regardless of the degree of native likeness of the non-native structures. The advantage of this approach lies in reducing the number of structures with decreasing energy, which should ensure the searchability of the potential. The method was tested on two proteins, PDB ID codes and, with an off-lattice united-residue force field. For, the search of the conformational space with the use of the conformational space annealing method and the newly optimized potential-energy function found the native structure very quickly, as opposed to the potential-energy functions obtained by former optimization methods. After even incomplete optimization, the force field obtained by using located the native-like structures of two peptides, and betanova (a designed three-stranded beta-sheet peptide), as the lowest-energy conformations, whereas for the 46-residue N-terminal fragment of staphylococcal protein A, the native-like conformation was the second-lowest-energy conformation and had an energy 2 kcal/mol above that of the lowest-energy structure.

Algorithms↗