Effects of varied energy density of complementary foods on breast-milk intakes and total energy consumption by healthy, breastfed Bangladeshi children

BACKGROUND: Information is needed to design studies of the effects of complementary feeding regimens on children's intakes of complementary foods (CFs) and breast milk. OBJECTIVE: We evaluated the effects of varied energy density of CFs on the time until stabilization of dietary intakes and on total daily energy intakes (EIs) and breast-milk intakes. DESIGN: CFs with low [0.4 kcal/g (LD)] and high [1.5 kcal/g (HD)] energy density were fed 3 times/d to 10 children (aged 9-18 mo) during 2 randomly assigned sequences of three 8-d diet periods (HD-LD-HD or LD-HD-LD) along with ad libitum breastfeeding. CF and breast-milk intakes were measured. RESULTS: Intakes of the HD diet and breast milk did not vary by day of period, but intake of the LD diet increased progressively. During days 5-7 of the last 2 diet periods in each sequence, more of the LD than of the HD diet was consumed (752 +/- 252 and 439 +/- 111 g/d, respectively; P < 0.001), but EIs from CFs were greater with the HD diet. Breast-milk consumption was slightly less (192 +/- 115 and 234 +/- 121 g/d, respectively; P = 0.03) but total daily EI was greater (774 +/- 175 and 441 +/- 85 kcal/d, respectively; P < 0.001) during the HD than during the LD diet period. CONCLUSIONS: New information on the effects of newly introduced diets on daily intakes of these diets and of breast milk can be used to design future studies. Total daily EIs were greater with the HD diet despite its negative effects on breast-milk intakes.     

Effects of dietary viscosity and energy density on total daily energy consumption by young Peruvian children.

BACKGROUND: Results of prior studies of the effect of viscosity reduction of high-energy-density, starch-containing diets on young children's energy intakes are inconsistent, possibly because of differences in the characteristics of the unmodified diets with which the low-viscosity diets were compared. OBJECTIVE: Our objective was to determine the effects of dietary viscosity and energy density on total daily energy consumption by young, non-breast-fed children. DESIGN: We measured the amount of food consumed and the duration of meals during 3 substudies, in each of which 3 study diets were offered for 4 consecutive days each in random sequence: high energy density, high viscosity (HD-HV); high energy density, low viscosity (HD-LV); and low energy density, low viscosity (LD-LV). The viscosity and energy density of the unmodified starch-containing HD-HV diet were varied across substudies to determine whether the effect of amylase liquefaction was related to the initial characteristics of the HD-HV diet. The viscosity of the HV diets ranged from 79000 to 568000 mPa s; energy density of the HD diets ranged from approximately 4.18 to 4.93 kJ (1.00-1.18 kcal)/g. Viscosity of the LV diets was approximately 3000 mPa s and the energy density of the LD diets was approximately 2.47 kJ (0.6 kcal)/g. RESULTS: In each substudy, children consumed more of the LD-LV diet (g kg body wt(-)(1) d(-)(1)) than of the other diets and more of the HD-LV diet than of the HD-HV diet (P < 0.001). Energy consumption from the HD-LV diet was greater than from the other diets (P < 0.001), but the energy intakes from the latter diets were not significantly different. CONCLUSION: Amylase liquefaction of HD-HV porridges resulted in increased energy consumption by young children.     

Adaptation to a marginal intake of energy in young children

Six male children, aged 8-28 months, were studied for three consecutive periods of 1 week each. They were given diets that provided 1.7 g protein/kg per d and supplements of minerals and vitamins, with a metabolizable energy intake during the 1st, 2nd and 3rd week of 419, 293 and 335 kJ (100, 70 and 80 kcal)/kg per d, diets 1, 2 and 3 respectively. All the food offered was consumed. Each child was weighed at the same time each day on an electronic balance. On the 6th and 7th day of each study period urine and stool were collected for 24 h to assess nitrogen balance. Using linear regression analysis it was shown that all children gained weight on diet 1, 2.3 (SD 1.3) g/kg per d, and five of six children gained weight on diet 3, the mean for the whole group being 2.7 (SD 2.3) g/kg per d, not significantly different. On diet 2 all children lost weight, -5.4 (SD 1.3) g/kg per d, highly significantly different from each of the other dietary periods. Using asymptotic regression analysis it could be shown that the rate of weight loss during the first part of the week on diet 2, -11 g/kg per d, was greater than at the end of the week, -2 g/kg per d, with a tendency towards a steady weight by day 7. Apparent N retention (mg/kg per d) was positive at the end of each of the three dietary periods: diet 1, 112 (SD 25); diet 2, 54 (SD 34); diet 3, 82 (SD 20). In five of the six children there was a marked reduction in stool frequency on diet 2 compared with diet 1, that was maintained to the period on diet 3. The findings suggest that during the period on diet 2 there was a saving of energy of the order of 105 kJ (25 kcal)/kg per d, which lasted through into the period on diet 3.     

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 female rats defend "appropriate" energy intake after adaptation to dietary energy

OBJECTIVE: To determine if adult female rats adapt to lower and higher dietary energy density. RESEARCH METHODS AND PROCEDURES: Study 1 compared high-fat (56%), high-energy density (HD) (21.6 kJ/g) and high-fat (56%), low-energy density (LD) (16.0 kJ/g) diets before surgery (two groups, 2 weeks, n = 16) and after surgery [ovariectomy (O) Sham (S); 2 x 2 factorial, n = 8; 6 weeks]. The second study (no surgery) compared high-fat (60.0%), high-energy (22.0 kJ/g) and low-fat (10.0%), low-energy (15.1 kJ/g) diets (n = 8). RESULTS: In study 1, food intake was similar for the first 2 weeks, but rats on the LD diet consumed less energy, gained less weight, and had lower nonfasted serum leptin (all p < 0.0001) than rats on the HD diet. After surgery, rats on the LD and HD diets had similar weight gain, but rats on the LD diet consumed more food (p < 0.0001) and less energy (p < 0.009). O rats consumed more food and gained more weight (p < 0.0001) than S rats. Results from study 2 were similar to those from study 1. DISCUSSION: The results demonstrated that O and S surgery rats and rats with no surgery adjust their food intake to defend a level of energy intake. This defense only occurred after a 2-week adaptation period. The major differences in final body weights and abdominal fat resulted from the initial 2 weeks before adaptation to energy density. Rats fed higher-energy diets seemed to "settle" at a higher level of adiposity, and rats fed lower-energy diets consumed more food to increase energy consumption.     

Dietary Studies of Children: The Bogalusa Heart Study Experience

For more than 20 years the Bogalusa Heart Study has been collecting data on children's dietary intakes in a biracial community. The macronutrient contribution of children's diets is similar to that in diets of adolescents: 13% of energy from protein, 49% from carbohydrate, and 38% from fat. As children get older, mean intakes of vitamins and minerals per 1,000 kcal decrease. Ten-year-old children in 1987-1988 were 3 lb heavier than 10-year-olds in 1973-1974. Yet total energy intakes remained virtually the same from 1973 to 1988. The composition of macronutrients shifted over the 15-year period, with an increase in the percentage of energy from protein and carbohydrate and a decrease in the percentage of energy from total fat, particularly saturated fat. Dietary cholesterol intake also decreased as a result of a decrease in egg consumption. Although the diets of children changed positively from 1973 to 1988, more than 75% of children consumed more total fat, saturated fat, and cholesterol than the recommended amounts. School meals had a major impact on the diets of children. School breakfast and lunch, together, contributed approximately 50% of the day's total intake of energy, protein, cholesterol, carbohydrate, and sodium. About 40% of daily total fat intake came from school breakfast and lunch. The diets of children in the Bogalusa study are similar to those reported in national studies of children. What might be different, however, are the types of foods consumed and their contribution to intakes of specific nutrients. An understanding of the diet and nutrition habits of children is critical to the planning of intervention strategies that will assist us in meeting our dietary goals for Healthy People 2000. J Am Diet Assoc. 1995; 95:1127-1133.     

Four-day multimedia diet records underestimate energy needs in middle-aged and elderly women as determined by doubly-labeled water

Systematic problems exist in the quantification of food intake in populations using traditional self-reported measures. The objective of this study was to determine the effectiveness of an innovative multimedia diet record (MMDR) for dietary energy intake assessment. Dietary intake was estimated by combining the use of a microcassette tape recorder and 35-mm camera in 53 women whose ages ranged from 50 to 93 y (64.9 +/- 11.3 y), with body weights of 62.4 +/- 12.2 kg and body mass indexes (BMI) of 24.4 +/- 4.0 kg/m(2). Using household measures, subjects voice-recorded and photographed all food and beverages consumed for four consecutive days. A two-point doubly-labeled water (DLW) method was used over 13 d to calculate carbon dioxide production, total body water, and subsequently, total energy expenditure (TEE) through the use of a food quotient. Mean body weight did not change between d 1 and 14. TEE and reported energy intake were compared using MMDR. Mean reported energy intakes 7.5 +/- 1.9 MJ/d (1774 +/- 476 kcal/d) were lower (P < 0.01) than TEE by 10.4 +/- 3.1 MJ/d (2477 +/- 736 kcal/d), indicating underreporting of food intake. Reporting accuracy (reported energy intake/TEE' 100%) was 76.0 +/- 22.9%. Mean energy expenditure (MJ/d), as determined by doubly-labeled water, was higher (P < 0.01) in each stratified age range when compared to reported energy intake by MMDR. There were no significant differences in reporting accuracy among the stratified age groups. Using the MMDR method, this population of weight-stable women underreported their food intakes compared to their determined energy expenditure estimated by DLW.     

Metabolizable energy of diets low or high in dietary fiber from cereals when eaten by humans

The metabolizable energy (ME) of two diets that differed in their content of dietary fiber (DF) from cereal products was measured in balance experiments in six human subjects. DF intake was 19.7 g/d with the low fiber diet and 48.3 g/d with the high fiber diet. Daily gross energy intakes were 2114 kcal (8845 kJ) and 2341 kcal (9795 kJ)/d with the low and the high fiber diets, respectively. DF contributed 83 kcal (347 kJ) and 203 kcal (849 kJ) to daily gross energy intake with the low and the high fiber diets, respectively, when heat of combustion of DF of 4.2 kcal (17.6 kJ)/g was assumed. Increasing the intake of DF resulted in an increase in stool weight and a greater fecal energy loss. Total energy losses were 253 kcal (1056 kJ) and 409 kcal (1711 kJ)/d with the low and the high fiber diets, respectively. ME provided by the low and the high fiber diet were 1861 kcal (7786 kJ) and 1932 kcal (8083 kJ)/d. The total increase in energy losses due to the increase in DF consumption exceeded the gross energy provided by additional DF. Compared with the low fiber diet, ME provided by protein and fat was decreased during the high fiber diet. Calculation of the apparent digestibility of DF indicated that fiber may have provided ME in the form of short-chain fatty acids during the low as well as during the high fiber intake. However, estimation of the amount of fecal gross energy indicated that available components of the diet, such as starch, must have been utilized incompletely during both experimental periods.     

Effects of protein and energy on dietary selection and protein utilization in rats with ventromedial hypothalamic lesions

The effect of bilateral destruction of the ventromedial hypothalamus (VMH) on protein and energy intakes was examined in relation to protein utilization. In Experiment 1, rats with VMH lesions were allowed to select protein (either casein or wheat gluten) and energy from two diets containing 70% and 5% protein, respectively. In Experiment 2, they were restricted to 0, 100 and 200 mg N/day of protein and given free access to protein-free diet. In Experiment 3, they were restricted to 2 and 5 g/day of protein-free diet but given 92% protein diet ad libitum. Self-selecting rats with VMH lesions consumed about 100 kcal/day regardless of the protein source, in contrast to sham-operated controls which consumed 75 kcal/day. They showed increased non-protein energy intake with constant protein consumption resulting in normal protein retention with increased body fat. When protein intake was restricted to 200 mg N/day, energy intake was reduced in animals given diet containing wheat gluten more than in those given diet containing casein, resulting in lower protein utilization. Therefore, food intake depended upon the amount of dietary protein. Rats with VMH lesions showed an exaggerated response to the ratio of protein to energy in the diet and consumed more energy from balanced diet but showed more reduction in food intake than controls in response to diet with an inappropriate ratio of protein to energy. The present study confirmed that the VMH was related to regulation of energy intake but not protein intake. It is suggested that protein intake is regulated in relation to maintenance of body protein in rats with VMH lesions as well as in normal rats.     

Effects of common illnesses on infants' energy intakes from breast milk and other foods during longitudinal community-based studies in Huascar (Lima), Peru

To assess the effects of common infections on dietary intake, 131 Peruvian infants were observed longitudinally. Home surveillance for illness symptoms was completed thrice weekly, and food and breast-milk consumption was measured during 1615 full-day observations. Mean (+/- SD) energy intakes on symptom-free days were 557 +/- 128 kcal/d (92.4 +/- 26.5 kcal.kg-1.d-1) for infants aged less than 181 d and 638 +/- 193 kcal/d (77.7 +/- 25.7 kcal.kg-1.d-1) for infants aged greater than 180 d. Statistical models controlling for infant age, season of the year, and individual showed significant 5-6% decreases in total energy intake during diarrhea or fever. There were no changes with illness in the frequency of breast-feeding, total suckling time, or amount of breast-milk energy consumed. By contrast, energy intake from non-breast-milk sources decreased by 20-30% during diarrhea and fever, and the small decrements in total energy consumption during illness were explained entirely by reduced consumption of non-breast-milk foods.     

Metabolizable energy of diets low or high in dietary fiber from fruits and vegetables when consumed by humans

The metabolizable energy (ME) of two diets, which differed in their content of dietary fiber mainly from fruits and vegetables, was determined in balance experiments in eight young women. The ME of the diets was also calculated by the specific factors of Merrill and Watt, by the general factors of Atwater, by the modification of Atwater's procedure used in the Federal Republic of Germany, and also by the equations of Southgate, of Miller and Payne, and of Miller and Judd. The daily intake of fruits, vegetables and potatoes was 505 and 1235 g with the low and the high fiber diets, respectively. Normally, young German women consume only 350 g of these foods each day. Dietary fiber intake was 18.8 g/d with the low fiber diet and 52.0 g/d with the high fiber diet. Daily gross energy intakes were 8540 and 8916 kJ (2041 and 2131 kcal) with the low and the high fiber diets, respectively. The apparent digestibility of energy was lower when the high fiber diet was consumed. Measured ME was 7665 and 7544 kJ/d (1831 and 1802 kcal/d) with the low and high fiber diets, respectively. It was calculated that fiber from fruits and vegetables contributed to ME about 3 kJ (0.7 kcal) per gram of fiber. On the average, the ME of the low fiber diet could be predicted by all calculation procedures except the formula of Miller and Judd. The ME of the high fiber diet could best be predicted by the specific factors of Merrill and Watt and by the Southgate formula.     

Relationship between the nutritional efficacy of a rice and bean diet and energy intake in preschool children.

Nitrogen balance and urea excretion were measured in a group of 4- to 6-year-old children receiving a rice and bean diet providing 1 g of protein per kilogram of body weight per day and three levels of calories. With diets providing 2300 and 3000 kcal/day, nitrogen retention was 41.16 +/- 29.04 and 53.30 +/- 18.46 mg/kg of body weight per day, respectively. With 1400 kcal/day, diet nitrogen retention decreased to 25.38 +/- 13.88 mg/kg body weight and urea nitrogen excretion increased. The importance of adequate caloric intake for optimum utilization of dietary protein from a rice and bean diet for growing children is demonstrated.     

Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression 1

BACKGROUND: It is unclear whether low-carbohydrate, high-protein, weight-loss diets benefit body mass and composition beyond energy restriction alone. OBJECTIVE: The objective was to use meta-regression to determine the effects of variations in protein and carbohydrate intakes on body mass and composition during energy restriction. DESIGN: English-language studies with a dietary intervention of > or =4200 kJ/d (1000 kcal/d), with a duration of > or =4 wk, and conducted in subjects aged > or =19 y were considered eligible for inclusion. A self-reported intake in conjunction with a biological marker of macronutrient intake was required as a minimum level of dietary control. A total of 87 studies comprising 165 intervention groups met the inclusion criteria. RESULTS: After control for energy intake, diets consisting of < or =35-41.4% energy from carbohydrate were associated with a 1.74 kg greater loss of body mass, a 0.69 kg greater loss of fat-free mass, a 1.29% greater loss in percentage body fat, and a 2.05 kg greater loss of fat mass than were diets with a higher percentage of energy from carbohydrate. In studies that were conducted for >12 wk, these differences increased to 6.56 kg, 1.74 kg, 3.55%, and 5.57 kg, respectively. Protein intakes of >1.05 g/kg were associated with 0.60 kg additional fat-free mass retention compared with diets with protein intakes < or =1.05 g/kg. In studies conducted for >12 wk, this difference increased to 1.21 kg. No significant effects of protein intake on loss of either body mass or fat mass were observed. CONCLUSION: Low-carbohydrate, high-protein diets favorably affect body mass and composition independent of energy intake, which in part supports the proposed metabolic advantage of these diets.     

Effect of low- and high-calcium dairy-based diets on macronutrient oxidation in humans

OBJECTIVE: Higher calcium and dairy intakes may be associated with lower body weights, but a mechanism in humans has yet to be elucidated. We compared the effects of a dairy-based high-calcium diet and a low-calcium diet on macronutrient oxidation. RESEARCH METHODS AND PROCEDURES: Subjects (10 men and nine women) consumed a low-dairy (LD, approximately one serving per day, approximately 500 mg Ca(2+)/d) or high-dairy (HD, approximately three to four servings per day, approximately 1400 mg Ca(2+)/d) energy balance diet for 1 week. Each diet condition was performed twice. On the 7th day, subjects were studied in a room calorimeter under one of four study conditions, applied in a randomized crossover design. Within each diet condition, subjects were studied under conditions of energy balance and acute energy deficit. The deficit (-600 kcal/d) was induced only for the 24 hours that subjects resided in the room and was achieved by a combination of caloric restriction and exercise. RESULTS: Under energy balance conditions, there was no effect of diet treatment on respiratory quotient or 24-hour macronutrient oxidation. Under energy deficit conditions, 24-hour fat oxidation was significantly increased on the HD diet (HD with deficit = 136 +/- 13 g/d, LD with deficit = 106 +/- 7 g/d, p = 0.02). DISCUSSION: Consumption of a dairy-based high-calcium diet increased 24-hour fat oxidation under conditions of acute energy deficit. We hypothesize that these effects are due to an increased fat oxidation during exercise.     

Adaptation of energy metabolism of overweight women to alternating and continuous low energy intake

To investigate whether a slimming diet based on alternating (low with normal) energy intakes could counteract a decrease in energy requirement, 24-h energy expenditure (24EE), sleeping energy expenditure (sleeping EE), and physical activity were determined in a respiration chamber in 27 overweight women: before weight reduction and after 4 and 8 wk of slimming. Daily alternating and continuous slimming diets were supplied. Average weight losses over 8 wk of slimming were 6.9-9.0 kg. After 8 wk at low energy intake, 24EE had declined by 12-16% (from 2328 +/- 219 to 1987 +/- 204 kcal, mean +/- SD). Sleeping EE had declined by 7-13% (from 64 +/- 6 to 57 +/- 6 kcal/h). Measurements of physical activity indicated a reduction of spontaneous physical activity during slimming. Alternating low energy intake did not prevent 24EE from declining. The reduction in 24EE was determined by a decrease of body weight, dietary induced thermogenesis (in proportion to caloric restriction), and physical activity. There seems little reason to consider other adaptive mechanisms.     

Dietary adherence and associated glycemic control in families of young children with type 1 diabetes

OBJECTIVE: This study examined the dietary intake, dietary adherence, and associated daily glycemic control of young children (mean age 5.6+/-1.6 years) with type 1 diabetes in 33 families. DESIGN: This was a one-sample cross-sectional study. Children's nutrient and energy intakes were measured using 3-day diet diaries. Children's mean daily blood glucose levels were assessed prospectively for 2 weeks using the FreeStyle (TheraSense, Inc, Alameda, CA) home blood glucose meter. STATISTICAL ANALYSIS: Means, standard deviations, and frequencies described the sample. Associations between dietary adherence and glycemic control were examined by one-tailed Pearson correlations. RESULTS: Mean nutrient intakes were less than the Dietary Reference Intake for children's intake of vitamin B-12 and calcium. Children's dietary deviations revealed better-than-predicted adherence to the number and timing of feedings per day and number of carbohydrate units consumed per meal. In contrast, children's daily carbohydrate intake was approximately 80%+/-21% of the recommended levels based on their weight and age. In addition, children's energy intake was only 78%+/-18% of the recommended levels based on age. Correlations revealed a positive association between poor dietary adherence and higher blood glucose levels. CONCLUSIONS: Young children with type 1 diabetes are likely to have adequate dietary intake of most micronutrients. However, their adherence to specific carbohydrate and energy intake recommendations may be lower. Because the preschool years represent a period of rapid growth, diet plans for preschoolers with diabetes need to be revised often for optimal management of type 1 diabetes. Close adherence to dietary recommendations is one behavior that may improve blood glucose control in young children with diabetes.     

Changes in plasma somatomedin-C in response to ingestion of diets with variable protein and energy content

We have attempted to determine the relative importance of dietary intake of protein and energy in restoring plasma immunoreactive somatomedin-C (Sm-C) concentrations after fasting. Ten healthy human volunteers were fasted for 5 days, then divided into two refeeding groups. One group (variable energy) was refed 1.0 g protein/kg ideal body weight, and in 9-day sequences, 11, 18 and 25 kcal of energy/kg. The other group (variable protein) was given 35 kcal energy/kg, and in 9-day sequences, 0.2, 0.4, and 1.0 g protein/kg. When subjects were refed the variable energy diets there was no significant increase in Sm-C at 11 kcal/kg (0.47 +/- 0.13 to 0.45 +/- 0.12 U/ml), suggesting that there is a threshold energy requirement below which optimal protein intake is not sufficient to raise the Sm-C. When subjects were refed 18 and 25 kcal/kg, it became apparent that the more energy added to the diet, the greater the absolute concentration of Sm-C attained (0.66 U/ml on 18 kcal/kg and 0.97 U/ml on 25 kcal/kg). Sm-C correlated with nitrogen balance (r = 0.58) during refeeding with the variable energy diets and was a good indicator of acute directional change in nitrogen balance. However, Sm-C was not a reliable indicator of nitrogen repletion, since it rose almost to control levels on the 25 kcal/kg diet while nitrogen balance remained slightly negative.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of amounts consumed on the digestion of cassava by young children

To determine whether increasing proportions of cassava could be consumed and satisfactorily digested, eight recovering malnourished children (20-38 mo old) received 25, 50 and 75% of their diet energy as freeze-dried cassava flour during 9-d periods, with intervening casein control diets. Enough casein was added to all cassava diets to bring protein energy to 8% of the total. When compared to the control diet, the 25% diet had no significant effect on consumption time or measures of protein and energy digestion. With the 50% diet, fecal wet and dry weights were moderately higher than with the 25% diet (196 +/- 44 and 24 +/- 4 vs. 121 +/- 36 and 16 +/- 3 g/d, respectively), as were fecal energy (89 +/- 16 vs. 63 +/- 16 kcal/d) and calculated carbohydrate (11 +/- 2 vs. 5 +/- 1 g/d); apparent nitrogen absorption (mostly from casein) was slightly lower (79 +/- 5 vs. 83 +/- 6%) and consumption time slightly higher (5-25, median 10, vs. 4-18, median 6 min/feeding). When energy from cassava was increased to 75%, fecal weights (240 +/- 49 and 31 +/- 5 g/d), energy (124 +/- 27 kcal/d) and carbohydrate (16 +/- 4 g/d) were all higher than when cassava provided 50 or 25% of energy. Consumption required 8-34, median 17 min/feeding and apparent nitrogen absorption was 76 +/- 6% of intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Voluntary food intake of lean and obese Zucker rats in relation to dietary energy and nitrogen content

Genetically obese (fa/fa) Zucker rats maintain a normal lean body size but deposit excessive amounts of body fat. Preferential use of substrates for lipid synthesis results in inefficient use of dietary nitrogen for protein deposition. Three studies were carried out to determine whether an increased protein requirement caused hyperphagia and whether young Zucker rats preferentially regulated protein or energy intake. Rats were offered isoenergetic diets with nitrogen contents ranging from 4.5 to 53.2 mg/g, or isonitrogenous diets with energy contents of 2.2, 3.3 or 4.2 kcal/g. In both situations obese rats had significantly higher food intakes than lean rats. Within phenotype the rats maintained an almost constant energy intake so that nitrogen intake was proportional to dietary nitrogen concentration. In a third experiment lean and obese rats were given different proportions of their control protein intake by stomach tube. Energy intake was determined by voluntary consumption of a protein-free diet. Within phenotype energy intake was the same for all levels of protein intake. It appears that obese Zucker rats regulate energy intake at an elevated level and that protein intake is determined by dietary nitrogen content. Hyperphagia does not appear to result from a desire to obtain protein.