Effects Of Dietary Energy Density Research Articles

Effects of dietary energy density and feeding strategy during the dry period on feed intake, energy balance, milk production, and blood metabolites of Holstein cows

Our study aimed to assess the effects of dietary energy density and strategy of delivery during the dry period on production and metabolic responses of Holstein cows free of displacement of abomasum, retained placenta, metritis, or hypocalcemia. Twenty-seven multiparous cows dried-off 50 d before calving were assigned randomly to 1 of 3 dietary treatments: a controlled energy, high-fiber diet [CE; 1.39 Mcal net energy for lactation (NEL)/kg of dry matter (DM)] formulated to supply 100% of the NEL requirement at ad libitum intake; or a higher energy diet (1.58 Mcal/kg) fed either at ad libitum (HE) or restricted (RE) intake to supply ∼150 or 80% of the NEL requirements, respectively. After calving, all cows were fed the same lactation diet. Cows were individually fed and remained in the study until 28 d postpartum. Data were analyzed using 2 contrasts: CE versus HE (effect of diet composition in cows fed for ad libitum DM intake) and HE versus RE (effect of ad libitum or restricted intake of the same diet). Prepartum intakes of DM and NEL as well as energy balance (EB), were greater for HE than CE and greater for HE than RE. Body weight (BW) gain was higher in HE than in RE, but CE and HE did not differ. Change in body condition score did not differ between CE and HE or HE and RE. Postpartum intakes of DM and NEL, EB, BW, body condition score, calf birth BW, milk yield, and milk components did not differ between CE and HE or HE and RE. Concentrations of glucose, insulin, nonesterified fatty acids, β-hydroxybutyrate, Ca, and Mg pre- and postpartum did not differ among diets. Although sample size was low, dry period plane of energy intake affected prepartum DM intake, EB, and BW gain but did not affect postpartum intakes of DM and NEL, yields of milk and milk components, or blood metabolites in healthy cows.

Effects of Dietary Energy Density in a Fermented Total Mixed Ration Formulated with Different Ratios of Rice Straw and Cassava Pulp on 2- or 14-Day-Aged Meat Quality, Collagen, Fatty Acids, and Ribonucleotides of Native Thai Cattle Longissimus Muscle.

This study investigated the effects of dietary energy density in rice straw and cassava pulp fermented total mixed ration on pH, cooking loss, Warner–Bratzler shear force (WBSF), and collagen content of 2- or 14-d-aged native Thai cattle (NTC) Longissimus thoracic (LT) muscles and fatty acids and ribonucleotides of 2-d-aged LT. Eighteen yearling NTC (Bos indicus) were randomly divided into three dietary treatments (T1 = 8.9, T2 = 9.7, and T3 = 10.5 MJ ME/kg), with six bulls per treatment. The results showed that T1 had the highest WBSF (p < 0.05). However, T2 had similar WBSF to T3 (p > 0.05). With aging, cooking loss increased (p < 0.01), while WBSF decreased (p < 0.01). Insoluble and total collagen decreased with aging (p < 0.05). Dietary energy density had no effect (p > 0.05) on collagen content, ribonucleotides and most fatty acids. However, T1 had more (p < 0.05) decanoic (C10:0), vaccenic (C18:1n9t), trans-linolelaidic (C18:2n6t), eicosatrienoic (C20:3n6), and docosadienoic (C22:2) acids than T2 and T3. In terms of lowest feed cost with comparable tenderness to T2 and highest energy density, T3 may be well suited for feeding NTC. Aging for 14 days improves LT tenderness, but its cooking loss may affect yield and juiciness.

Effects of dietary energy density and supplemental rumen undegradable protein on intake, viscera, and carcass composition of lambs recovering from nutritional restriction.

Variation in nutrition is a key determinant of growth, body composition, and the ability of animals to perform to their genetic potential. Depending on the quality of feed available, animals may be able to overcome negative effects of prior nutritional restriction, increasing intake and rates of tissue gain, but full compensation may not occur. A 2 × 3 × 4 factorial serial slaughter study was conducted to examine the effects of prior nutritional restriction, dietary energy density, and supplemental rumen undegradable protein (RUP) on intake, growth, and body composition of lambs. After an initial slaughter (n = 8), 124 4-mo-old Merino cross wethers (28.4 ± 1.8 kg) were assigned to either restricted (LO, 500 g/d) or unrestricted (HI, 1500 g/d) intake of lucerne and oat pellets. After 8 wk, eight lambs/group were slaughtered and tissue weights and chemical composition were measured. Remaining lambs were randomly assigned to a factorial combination of dietary energy density (7.8, 9.2, and 10.7 MJ/kg DM) and supplemental RUP (0, 30, 60, and 90 g/d) and fed ad libitum for a 12- to 13-wk experimental period before slaughter and analysis. By week 3 of the experimental period, lambs fed the same level of energy had similar DMI (g/d) and MEI (MJ/d) (P > 0.05), regardless of prior level of nutrition. Restricted-refed (LO) lambs had higher rates of fat and protein gain than HI lambs (P < 0.05) but had similar visceral masses (P > 0.05). However, LO lambs were lighter and leaner at slaughter, with proportionally larger rumens and livers (P < 0.05). Tissue masses increased with increasing dietary energy density, as did DMI, energy and nitrogen (N) retention (% intake), and rates of protein and fat gain (P < 0.05). The liver increased proportionally with increasing dietary energy density and RUP (P < 0.05), but rumen size decreased relative to the empty body as dietary energy density increased (P < 0.05) and did not respond to RUP (P > 0.05). Fat deposition was greatest in lambs fed 60 g/d supplemental RUP (P < 0.05). However, lambs fed 90 g/d were as lean as lambs that did not receive supplement (P0, P > 0.05), with poorer nitrogen retention and proportionally heavier livers than P0 lambs (P < 0.05). In general, visceral protein was the first tissue to respond to increased intake during refeeding, followed by non-visceral protein and fat, highlighting the influence of differences in tissue response over time on animal performance and body composition.

Effect of dietary energy density and folic acid supplementation on white striping occurrence and growth performance of broiler chickens

Broilers were allocated to eight treatments consisting of two energy levels: normal (NE) and high (HE), and four folic acid (FA) levels (2.2, 5, 10, and 15 ppm). On day 42, two male and two female chickens were euthanized per pen, and white striping (WS) evaluation was performed on the pectoralis major. Birds fed HE diets had reduced (P &lt; 0.05) feed intake and feed conversion rate than those on NE diets. With increasing FA levels, there was reduced (P &lt; 0.05) WS score and increased (P &lt; 0.05) normal breast fillet percentage in female chickens but not in the males. WS scores were higher (P &lt; 0.01) in male chickens than in the females.

Effect of Dietary Energy Density on Increasing Blood Glucose Pattern and Hunger-Satiety Sensation

Background: There was no data how these food density could effect on glucose and visual analog levels based on hunger-filled scales in Indonesian population. Objective To determine the effect of food energy density on glucose levels and hunger-satiety sensation. Material and Methods: Seventeen women 18-22 years of age with BMI&gt; 25, were given low energy density breakfast (n = 9) and high energy density (n = 7). The subjects were fasted for 10 hours, fasting blood glucose levels was measured as well as hunger-satiety sensation with a visual analog scale (VAS), prior to treatment. Breakfast was started at 08.00 a.m chew up to 32 times for 15 minutes. Blood glucose levels and VAS measurement were taken back in 2 hours and 4 hours afterward. Result: There was a significant differences in glucose levels between 4 hours postpandrial and 2 hours postpandrial (p = 0.031) and also between 4 hours postpandrial and fasting state (p = 0.042) in both groups. Analysis of hunger level VAS (p = 0.02) and satiety level VAS (0.04) at 4 hours postpandrial also differ significantly. Correlation analysis between hunger level VAS and blood glucose was different significantly (p = 0.01) with r = -0.59. Conclusions: The low energy density foods produce a pattern of increasing blood glucose levels were more stable, thus, more able to suppress the sensation of hunger than high energy density.

Gastric evacuation rates in farmed brook trout subjected to a range of feeding conditions fed commercial pellets

A previously parameterized gastric evacuation rate (GER) model of brook trout dStdt=−ρLL1.31St, where St is current stomach mass (g), L is total fish length (cm), t is time (h), and ρL is the rate parameter constant (g0.5 h−1), was extended to describe the effects of dietary energy density E (kJ g−1), temperature T (°C), feed storage conditions (frozen and non-frozen), and the arrival of an additional meal on GER of total stomach contents. The resulting data revealed a considerable effect of E and T while feed storage conditions and the arrival of an additional meal have no effect on GER of brook trout. The GER tends to increase as the energy contents of the diet were reduced. The relationship between GER and the energy contents of diet was described by a power function of E. The GER increased exponentially as the temperature increases to a maximum value at the optimum temperature (c. 18.9 °C) and then declines rapidly. The optimum temperature model adequately described this temperature dependency of the GER at both low and high temperatures. The estimated parameters of E and T were then added to the GER model of brook trout as dStdt=−0.000860L1.31E−0.41e0.08T1−e1.82T−20.6St (g h−1). The model was tested to predict the stomach fullness in brook trout fed for three consecutive days. The predicted values were closely in line with the actual values of stomach fullness (r2 = 0.987). This parameterized model can be used to predict levels of stomach fullness independent of meal size and timing, and should have useful applications in the development of feeding regimes for brook trout.

107 Effects of Dietary Energy Density and Intake on Energy Requirements in Beef Cows.

107 Effects of Dietary Energy Density and Intake on Energy Requirements in Beef Cows.

Effects of Dietary Energy Density in the Dry Period on the Production Performance and Metabolism of Dairy Cows

Thirty healthy Holstein dairy cows in the dry period were randomly divided into three groups and fed diets with different net energy for lactation (group A: 1.2 Mcal/kg DM, group B: 1.3 Mcal/kg DM, and group C: 1.4 Mcal/kg DM) for 8 weeks prepartum. Thereafter, dairy cows were fed a diet of the same formulation (1.66 Mcal/kg DM) for 12 weeks postpartum. The effects of different dietary energy densities in the dry period on postpartum performance and metabolic parameters of dairy cows were observed. Milk yield was reduced by 14.5% in the low-energy diet group; however, there were no differences in milk composition between the three groups. Postpartum plasma β-hydroxybutyrate, non-esterified fatty acid, growth hormone, and glucagon levels were significantly decreased whereas leptin and neuropeptide levels were elevated in the low-energy diet group. Moreover, body fat mobilization was attenuated, and the decline in postpartum body condition was reduced in the low-energy diet group, thus effectively reducing the postpartum negative energy balance.

Energy density and feeding frequency of complementary foods affects meal-specific food consumption and meal duration by healthy, breast fed Bangladeshi children

Background: Appropriate feeding of infants and young children is necessary to prevent growth faltering and optimize health during the first two years of life. There is little information on the effects of dietary energy density and feeding frequency of complementary foods on food consumption during individual meals and the amount of caregiver time expended in child feeding. Methods: During nine separate, randomly ordered dietary periods lasting 3-6 days each, we measured selfdetermined intakes of semi-solid cereal porridges by 18 healthy, breastfed children 8-11 months of age. The infants were fed coded porridges with energy densities of 0.5, 1.0 or 1.5 kcal/g, during three, four, or five meals/day. Complementary food intake was measured by weighing the feeding bowl before and after every meal. Results: Children consumed greater amounts of complementary foods per meal when they received diets with lower energy density and fewer meals per day. Greater time was expended per meal when fewer meals were offered. The time expended per meal did not vary with dietary energy density, but the children ate more and faster for the lower energy density diets. Conclusions: We conclude that the energy density and feeding frequency of complementary foods affect meal-specific food intake. Meal frequency also influences the duration of individual meals, but energy density does not. These results provide further evidence of young children’s ability to regulate their energy intakes, even during infancy, and convey information on factors that affect the amount of time that caregivers must devote to child feeding.

Changes in lipid metabolism and β-adrenergic response of adipose tissues of periparturient dairy cows affected by an energy-dense diet and nicotinic acid supplementation.

Dairy cattle will mobilize large amounts of body fat during early lactation as an effect of decreased lipogenesis and increased lipolysis. Regulation of lipid metabolism involves fatty acid synthesis from acetate and β-adrenergic-stimulated phosphorylation of hormone-sensitive lipase (HSL) and perilipin in adipocytes. Although basic mechanisms of mobilizing fat storage in transition cows are understood, we lack a sufficiently detailed understanding to declare the exact regulatory network of these in a broad range of dairy cattle. The objective of the present study was to quantify 1) protein abundance of fatty acid synthase (FAS), 2) extent of phosphorylation of HSL and perilipin in vivo, and 3) β-adrenergic stimulated lipolytic response of adipose tissues in vitro at different stages of the periparturient period. We fed 20 German Holstein cows an energy-dense or an energetically adequate diet prepartum and 0 or 24 g/d nicotinic acid (NA) supplementation. Biopsy samples of subcutaneous and retroperitoneal adipose tissue were obtained at d 42 prepartum (d -42) and at d 1, 21, and 100 postpartum (d +1, d +21, d +100, respectively). To assess β-adrenergic response, tissue samples were incubated with 1 μ isoproterenol for 90 min at 37°C. The NEFA and glycerol release, as well as HSL and perilipin phosphorylation, was measured as indicators of in vitro stimulated lipolysis. In addition, protein expression of FAS and extent of HSL and perilipin phosphorylation were measured in fresh, nonincubated samples. There was no effect of dietary energy density or NA on the observed variables. The extent of HSL and perilipin phosphorylation under isoproterenol stimulation was strongly correlated with the release of NEFA and glycerol, consistent with the functional link between β-adrenergic-stimulated protein phosphorylation and lipolysis. In the nonincubated samples, FAS protein expression was decreased at d +1 and d +21, whereas HSL and perilipin phosphorylation increased from d -42 to d +1 and remained at an increased level throughout the first 100 d of lactation. In vitro lipolytic response was significant in prepartum samples at times when in vivo lipolysis was only minimally activated by phosphorylation. These data extend our understanding of the complex nature of control of lipolysis and lipogenesis in dairy cows and could be useful to the ongoing development of systems biology models of metabolism to help improve our quantitative knowledge of the cow.

Effect of dietary energy density and meal size on growth performance, eating pattern, and carcass and meat quality in Holstein steers fed high-concentrate diets

A total of 121 steers (162 ± 3.0 kg BW and 148 ± 2.7 d old) were used to study the effect of dietary energy density and meal size (limiting the amount of concentrate delivered at each feeder visit) on performance, hormones associated with the regulation of intake, and carcass and meat quality. Steers were allocated by BW to 6 pens. Each pen had the same BW mean and CV, and pens were randomly assigned to 3 treatments (2 pens/treatment): a concentrate of moderate energy density (3.23 Mcal ME/kg, 6.2% ether extract) fed for ad libitum intake with no control on meal size (CTR), a concentrate of high-energy density (3.43 Mcal ME/kg, 8.3% ether extract) fed for ad libitum intake with no control on meal size (HE), and the same high-energy concentrate offered for ad libitum intake but with meal size limited to a maximum concentrate delivery of 0.6 kg DM/visit (HELM). Body weight was recorded every 14 d; concentrate consumption and eating pattern were recorded daily. On d 163, blood samples were collected to determine serum concentrations of leptin, ghrelin, glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), glucose, and insulin. After slaughter (on d 166 to 170), the 9-10-11 rib section was removed to estimate separable bone, lean, and fat. Meat quality of LM was analyzed. Data were analyzed using a mixed-effects model with repeated measures. Steers in the HELM treatment had a lower (P < 0.01) final BW and ADG than CTR and HE steers. Concentrate intake was greater (P < 0.001) in CTR (6.6 ± 0.10 kg/d) than in HE steers (5.7 ± 0.10 kg/d), and HELM (5.2 ± 0.10 kg/d) consumed less concentrate than CTR and HE steers. However, HE and HELM steers were more (P < 0.01) efficient than CTR steers. The mean number of daily meals and eating rate were less (P < 0.05) for HELM than for HE or CTR. At d 163, serum concentrations of GLP-1, CCK, and insulin were lower (P < 0.05), and leptin (P = 0.10) and glucose (P = 0.08) concentrations tended to be lower for HELM than for CTR or HE. Carcass conformation and HCW were less (P < 0.05) for HELM than for CTR. Although differences among treatments were observed in carcass fat cover, intramuscular fat did not differ among treatments. Limiting the amount of feed delivery per feeder visit in steers fed high-energy (fat) diets affected eating pattern, reduced total energy consumption and performance, and modified hormones related to intake compared with CTR and HE, but no effect on rib fat distribution and meat quality was observed.

Effects of dietary energy density and apparent ileal digestible lysine:digestible energy ratio on growth performance, meat quality, and peroxisome proliferator-activated receptor γ (PPARγ) gene expression of muscle and adipose tissues in Landrace×Rongchang crossbred pigs

This study was conducted to evaluate the effects of dietary digestible energy (DE) density (13.0 or 14.5MJ/kg) and apparent ileal digestible lysine:energy (Lys:DE) ratio (0.4, 0.5, and 0.6g/MJ) on growth performance, meat quality, and PPARγ gene expression of muscle and adipose tissues in Landrace×Rongchang crossbred pigs. One hundred and eight (71.22±0.04kg body weight) crossbred (Landrace×Rongchang) castrated male pigs were blocked by BW and allotted to 36 pens (three pigs per pen), and pens were randomly assigned within blocks to one of six dietary treatments arranged in a 2×3 factorial design, with two DE levels (13.0 or 14.5MJ/kg) and three Lys:DE ratios (0.40, 0.50, or 0.60g/MJ). Over the 46-d trial, dietary energy density had no effect on average daily gain (ADG) (P=0.48), however, pigs fed high-energy diets had decreasing average daily feed intake (ADFI) and the ratio of feed intake and gain (F/G) (P<0.05). Feeding of the diet with the highest Lys:DE ratio resulted in increased F/G (P<0.05) compared with other experimental diets. Increasing energy density increased hot carcass, dressing percentage and intramuscular fat (IMF) content (P<0.05). Furthermore, IMF content decreased with increasing Lys:DE ratio (P<0.05). An energy density×Lys:DE ratio interaction on slaughter weight and shearing force was observed (P<0.05). In addition, pigs fed 14.5MJ/kg had decreasing IMF content as Lys:DE ratio increased (linear and quadratic, P<0.05), but increasing muscle pH45min (linear, P<0.05). There was a quadratic effect on shearing force (P<0.05) as Lys:DE ratio increased for pigs fed 13.0MJ/kg. Increasing dietary DE enhanced the expression of PPARγ (P<0.05) in muscle tissues, whereas the mRNA levels of PPARγ decreased (P<0.05) as Lys:DE ratio increased. The results of this study indicated that a reasonably reduced Lys:DE ratio diet increased intramuscular fat deposition and improved pork tenderness. This could be partly related to the increased gene expression of PPARγ in muscle tissues.

Effects of Dietary Energy Density on Serum Adipocytokine Levels in Diabetic Women

This study was aimed to assess the effect of dietary energy density (kcal/g) on serum levels of adipocytokines of type 2 diabetic women. In this randomized parallel design clinical trial, a total of 60 diabetic women (aged 30-60 years; BMI>25 kg/m²) were assigned to consume either a low-energy dense (LED) (65% of energy from carbohydrates and 25% from fats), normal-energy dense (NED) (60% from carbohydrates, 30% from fats), or high-energy dense (HED) diet (55% from carbohydrates and 35% from fats) for 8 weeks. The low-energy dense diet was rich in fruits, vegetables, whole grains, and water, while the high-energy dense diet was rich in fats and oils and limited in fruits and vegetables as compared with the normal-dense diet. At baseline and at the end of intervention fasting blood samples were taken to assess metabolic profile. Women in the LED group consumed significantly more dietary fiber (p<0.001), fruits (p<0.001) and vegetables (p<0.001) than those in the NED and HED groups. We failed to find a significant effect of dietary energy density (kcal/g) on serum adiponectin and visfatin levels. Even the within-group changes in serum adiponectin and visfatin levels were not significant. Consumption of LED and NED diets resulted in a significant increase in serum chemerin levels (p=0.04). Comparison of mean changes of serum chemerin levels across 3 groups revealed a significant difference (p=0.04). Our study provides evidence indicating that consumption of HED diet for 8 weeks among diabetic patients prevented the increase in serum chemerin levels compared with LED and NED diets. Furthermore, we found no significant effect of dietary energy density (kcal/g) on serum adiponectin and visfatin concentrations in the current study.

Effects of dietary energy density on nutrient digestibility, performance and carcass characteristics of Morada Nova lambs

Foram avaliados os efeitos de diferentes niveis de energia metabolizavel (EM) sobre a digestibilidade e caracteristicas de carcaca em cordeiros Morada Nova. Utilizaram-se 40 cordeiros Morada Nova, com peso inicial de 12,2 ± 2,05 kg. Cinco tratamentos foram definidos de acordo com os niveis de energia metabolizavel (0,96; 1,28; 1,72; 2,18 e 2,62 Mcal/kg MS), conduzidos em delineamento de blocos ao acaso. Os animais foram abatidos quando a media de peso corporal (PC) do grupo atingiu 25 kg. Foi observado efeito linear para o coeficiente de digestibilidade da MS, MO, EE, PB, FDN, CT, FC e NFC. O ganho de peso diario (GPD) apresentou aumento linear (P<0,0001) com os niveis de EM. O maior GPD observado foi de 135,98 g/dia para o nivel de 2,62 Mcal/kg MS. As caracteristicas de carcaca avaliadas (peso de carcaca quente, peso de carcaca fria, perda por resfriamento em kg e rendimento biologico) nao variaram em funcao dos niveis de EM, com valores medios de 11,52; 11,03; 0,48 e 57,25, respectivamente. Conclui-se que o incremento do nivel de energia em dietas influencia a digestibilidade dos nutrientes e ganhos de peso diario de cordeiros Morada Nova, durante o periodo de crescimento, sem alterar as caracteristicas de carcaca.

Effects of dietary energy density on nutrient digestibility, performance and carcass characteristics of Morada Nova lambs

Foram avaliados os efeitos de diferentes níveis de energia metabolizável (EM) sobre a digestibilidade e características de carcaça em cordeiros Morada Nova. Utilizaram-se 40 cordeiros Morada Nova, com peso inicial de 12,2 ± 2,05 kg. Cinco tratamentos foram definidos de acordo com os níveis de energia metabolizável (0,96; 1,28; 1,72; 2,18 e 2,62 Mcal/kg MS), conduzidos em delineamento de blocos ao acaso. Os animais foram abatidos quando a média de peso corporal (PC) do grupo atingiu 25 kg. Foi observado efeito linear para o coeficiente de digestibilidade da MS, MO, EE, PB, FDN, CT, FC e NFC. O ganho de peso diário (GPD) apresentou aumento linear (P&lt;0,0001) com os níveis de EM. O maior GPD observado foi de 135,98 g/dia para o nível de 2,62 Mcal/kg MS. As características de carcaça avaliadas (peso de carcaça quente, peso de carcaça fria, perda por resfriamento em kg e rendimento biológico) não variaram em função dos níveis de EM, com valores médios de 11,52; 11,03; 0,48 e 57,25, respectivamente. Conclui-se que o incremento do nível de energia em dietas influencia a digestibilidade dos nutrientes e ganhos de peso diário de cordeiros Morada Nova, durante o período de crescimento, sem alterar as características de carcaça.

Effect of Dietary Energy Density on Performance and Lean Deposition of Growing-Finishing Pigs

Effect of Dietary Energy Density on Performance and Lean Deposition of Growing-Finishing Pigs

Dietary energy density and weight regulation.

Dietary energy density (ED) has been suggested as an important determinant of energy intake and, therefore, energy regulation. This review summarizes published studies on the effects of dietary ED on hunger, satiety, energy intake, and body weight in healthy individuals, and compares the relative effects of ED manipulated by dietary fat only, fat and fiber, water, and type of sweetener. In short-term studies, consumption of low-ED foods promotes satiety, reduces hunger, and decreases energy intake with no marked differences between different dietary manipulations used to change ED. In addition, low-ED diets promote moderate weight loss in long-term studies. In studies lasting longer than 6 months, weight loss was more than three times as great in individuals consuming diets both low in fat and high in fiber compared with diets only low in fat (-3.4 kg versus -1.0 kg). Combined, these studies suggest that diets low in fat and high in fiber may be the most effective low-ED diets for promoting weight loss. Further research is needed on the effects of dietary ED by changing water or sweetener content.

The relationship between dietary energy density and energy intake

Much of the research in ingestive behavior has focused on the macronutrient composition of foods; however, these studies are incomplete, or could be misleading, if they do not consider the energy density (ED) of the diet under investigation. Lowering the ED (kcal/g) by increasing the volume of preloads without changing macronutrient content can enhance satiety and reduce subsequent energy intake at a meal. Ad libitum intake or satiation has also been shown to be influenced by ED when the proportions of macronutrients are constant. Since people tend to eat a consistent weight of food, when the ED of the available foods is reduced, energy intake is reduced. The effects of ED have been seen in adults of different weight status, sex, and behavioral characteristics, as well as in 3- to 5-year-old children. The mechanisms underlying the response to variations in ED are not yet well understood and data from controlled studies lasting more than several days are limited. However, both population-based studies and long-term clinical trials indicate that the effects of dietary ED can be persistent. Several clinical trials have shown that reducing the ED of the diet by the addition of water-rich foods such as fruits and vegetables was associated with substantial weight loss even when patients were not told to restrict calories. Since lowering dietary energy density could provide effective strategies for the prevention and treatment of obesity, there is a need for more studies of mechanisms underlying the effect and ways to apply these findings.

Prospective study of dietary energy density and weight gain in women

BackgroundLittle is known about the long-term effects of dietary energy density (ED) on weight gain. ObjectiveThe objective was to assess the long-term relation between changes in dietary ED and age-related weight gain. DesignWe conducted a prospective study of 50 026 women (x̄ ± SD age: 36.5 ± 4.6 y) in the Nurses’ Health Study II followed from 1991 to 1999. Dietary ED and body weight were ascertained in 1991, 1995, and 1999. Total dietary ED was calculated by dividing each subject's daily energy intake (kcal) by the reported weight (g) of all foods consumed. ResultsDietary ED was positively correlated with saturated fat (r = 0.16), trans fat (r = 0.15), and the glycemic index (r = 0.16), but was inversely correlated with vegetable protein (r = −0.30), vegetables (r = −0.27), and fruit (r = −0.17). ED was not significantly correlated with total fat intake as a percentage of energy (r = 0.08). Women who increased their dietary ED during follow-up the most (5th quintile) had a significantly greater multivariate-adjusted weight gain than did those who decreased their dietary ED (1st quintile) (8-y time period: 6.42 kg compared with 4.57 kg; P for trend < 0.001). However, the amount of weight change over time varied considerably according to the ED values of individual foods and beverages. ConclusionA high dietary ED reflects a dietary pattern higher in saturated and trans fats and refined carbohydrates. Increases in dietary ED were associated with greater weight gain among middle-aged women during 8 y of follow-up. However, public health recommendations cannot be made simply on the basis of ED values of individual foods and beverages.

Effects of dietary energy density and L-carnitine supplementation on growth performance, carcass traits and blood parameters of broiler chickens

The present study was conducted to determine the effects of dietary metabolisable energy (ME) density and L-carnitine supplementation on the performance, carcass traits and blood parameters of broiler chickens. The experiment was designed with three levels of dietary energy (low, medium and high) and two levels of L-carnitine (0 and 100 mg/kg diet) in a 3x2 factorial arrangement. L-carnitine supplementation did not significantly affect body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). However, FCR and BWG showed a significant improvement as dietary energy density increased. No significant interactions were observed between energy density and L-carnitine supplementation in the performance and carcass parameters studied in the study. Carcass yield and proportion of carcass sections were not affected significantly by any of the treatments. Chemical composition of the leg (thigh and drumstick) and breast muscle was not significantly influenced by dietary energy or carnitine, with the exception of the dry matter (DM) content of breast muscle. A low ME diet caused a significant increase in the DM content of chicken breast muscle. Furthermore, blood parameters did not show any differences between treatments. However, aspartate aminotransferase (AST) activity in blood was elevated in chickens fed a high ME diet compared to those on a low ME diet. The results of the investigation showed that L-carnitine supplementation produced no significant improvement in broiler performance and meat quality. Higher levels of diet ME increased broiler performance, though no significant interactions could be found between energy and carnitine levels. South African Journal of Animal Science Vol. 37 (2) 2007: pp. 65-73