Increasing the protein content in a carbohydrate-free diet enhances fat loss during 35% but not 75% energy restriction in rats

The purpose of the present study was to test the influence of the amount of protein in a carbohydrate-free diet during a weight reducing program using severe (75%) or more moderate (35%) energy restriction in rats. In Expt. 1, 3 groups (n = 6) consumed ad libitum a high-carbohydrate, low-fat diet [P21C69L10 containing 21% of energy as protein (P21), 69% carbohydrate (C69) and 10% lipids (L10)], a high-carbohydrate, high-fat diet (P21C34L45), or a carbohydrate-free, high-fat, high-protein diet (P55L45). In Expt. 2, 7 groups (n = 7) were studied. For 20 d, groups 1-4 consumed ad libitum diets containing macronutrients at the proportions indicated in their designations [P14C56L30 (control diet), P30L70, P50L50, and P90L10]. Groups 5-7 were pair-fed the same diets at the level of the spontaneous intake of the P90L10 group on the previous day (35% energy restriction). In Expt. 3, 5 groups (n = 7) were fed 1 of the following diets for 20 d. Group 1 consumed the control diet (P14C56L30) ad libitum. Groups 2-5 were energy restricted to 25% of the daily energy intake of group 1 with diets varying in their protein and lipid concentrations (P14C56L30, P50L50, P70L30, and P90L10). A high-fat content in the diet devoid of carbohydrate did not increase energy intake and body adiposity and neither body weight nor body composition was significantly affected by the protein to lipid ratio when energy restriction was 75%; however, a protein content > 50% preserved lean body mass at the expense of fat mass when energy restriction was 35%. Our results show that the absence of carbohydrates from the diet induces a low energy intake and the preferential deposition of protein.     

Effect of selenium on rat growth, growth hormone and diet utilization.

Female rats were fed a selenium-deficient diet composed of Torula yeast, sucrose, vitamins (including tocopheryl acetate) and minerals from weaning and during breeding, gestation and lactation. The offspring were used to study the effects of selenium on growth, diet utilization and growth hormon status. The Torula yeast diet containing 200 IU dl-alpha-tocopheryl acetate was fed alone or supplemented with 0.025 or 0.1 ppm of selenium as selenite. Rats fed the selenium-supplemented diets grew significently faster and consumed significantly more diet than rats fed the unsupplemented diet. Anterior pituitary weights were lower in selenium-deficient rats, but if expressed per unit of body weight, were similar to pituitary weight of selenium-supplemented animals. Total growth hormone in the anterior pituitary was reduced in selenium-deficient rats. A metabolism study indicated that rats allowed ad libitum access to supplemented diets consumed more diet and obtained more metabolizable energy from the diet than rats fed the deficient diet. It the intake of rats fed the supplemented diets was limited to that of rats allowed ad libitum access to deficient diet, growth of rats was similar. However, metabolizable energy content of the diet increased quadratically and nitrogen digestibility increased linearly as thelevel of selenium increased. Selenium deficiency reduced growth primarily by decreased diet consumption, but also reduced the utilization of energy and nitrogen.     

Does the consumption of caloric and non-caloric beverages with a meal affect energy intake?

Beverages are frequently consumed with meals, but their influence on meal energy intake is not understood. We hypothesized that differences in the energy, nutrient content, and sensory properties of beverages consumed with a meal would affect intake. Forty-four women ate lunch in the laboratory once a week for 6 weeks. Lunch was consumed ad libitum, and was served with one of five beverages that were consumed in full, or no beverage. The beverages were 360 g of water, diet cola, regular cola, orange juice, and 1% milk. Results showed an effect of beverage type on meal intake (p<0.0001). Energy intake did not differ among the non-caloric and no-beverage conditions. Similarly, energy intake from lunch (including beverage) did not differ among the caloric beverage conditions. When a caloric beverage (156 kcal; 653 kJ) was consumed with the meal, energy intake was 104+/-16 kcal (435+/-67 kJ) greater than when a non-caloric beverage or no beverage was consumed. Subjects' ratings of fullness after lunch did not differ among the beverage conditions, but were lower for the no-beverage condition. These results show that when caloric beverages are consumed with a meal they add to energy intake from food, without significantly affecting satiety ratings.     

Effect of dietary protein and food restriction on milk production and composition, maternal tissues and enzymes in lactating rats

Lactating rats have been fed either a protein-restricted diet (10 vs. 20% casein in the control diet) or the control diet at 80, 60 and 40% of the voluntary intake for 7 d from d 7 of lactation. Food consumption, changes in maternal live weight, litter live weight gain and the mass of several maternal tissues were determined together with the activity of several mammary and liver enzymes, including 10 that are essential for fatty acid and complex lipid synthesis. Milk production was estimated from the litter weight gain and litter weight. Lactating rats fed the 20% protein diet ad libitum consumed three times that of nonlactating rats; their liver and kidney masses were significantly higher and their adipose mass was lower. The livers of the lactating rats were fatty, containing 118 mg lipid/g compared with 42 mg/g for the nonlactating rats. Lactating rats fed either the protein-restricted diet or the control diet at 40 and 60% of the ad libitum intake of the control diet had lower mammary, liver and kidney masses than rats consuming the control diet ad libitum. Both protein and food restriction led to lower rates of milk production than those of ad libitum-fed control rats as evidenced by the decrease in litter live weight gains. The concentrations of total lipid, total protein and lactose in milk were not affected by these dietary treatments. The concentration of alpha-lactalbumin in milk of rats fed the low protein diet was, however, lower than that in the milk of all rats receiving the control diet, irrespective of intake. Consumption of the restricted diets resulted in only small changes in specific activities (mu/mg protein) of 15 mammary enzymes. In the livers, lactation led to higher specific activities of all four soluble lipogenic enzymes examined but did not affect the particulate enzymes involved in complex lipid synthesis. The dietary restrictions resulted in lower specific activities of the soluble enzymes compared with those of the lactating rats consuming the control diet ad libitum without affecting the particulate enzymes. Total activities of these enzymes were, however, lower than those for the control rats as a result of the smaller liver mass in the rats receiving the restricted diets.     

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.     

Effect of the protein and oil contents on calcium utilization in the diets of female Fischer rats that were fed by three different feeding methods

We studied the effects of varying the protein and oil contents in the diet and three different feeding methods on the utilization of dietary calcium (Ca) in female Fischer rats. The experimental diets were based on the AIN-76 diet. Rats were fed one of nine experimental diets containing different levels of protein and oil. The experimental diets contained 10, 20 or 40% of protein (milk casein) and 5, 10 or 20% of soybean oil. The three meal feeding methods were ad libitum feeding, pair feeding and adjustable feeding. The experimental diets that were given by prepared feeding were supplemented with a mineral and vitamin solution. The effects of the protein and oil contents in the diet were analyzed by two-way ANOVA. Among rats that were fed ad libitum, the oil content in the diet affected the degree of mineral and vitamin intake. Among the rats fed ad libitum, the oil content in the diet had a significant effect on the level of Ca intake, although it did not have a significant effect on the level of energy intake. For pair feeding, the feeding volume was limited in each group; therefore, there was a significant difference in energy intake and there was no significant difference in Ca intake among each diet group. For adjustable feeding, there was considerable mineral and vitamin intake, which effected the reduction of feeding volume depending on the oil volume in the diet. There were no significant differences in the energy, Ca and other mineral and vitamin intakes among the nine groups that were fed using adjustable feeding. In analyzing two-way ANOVA, in which the parameters were the contents of protein and oil in the experimental diets, there were differences in Ca utilization among rats that were fed using the three feeding methods. This result was shown to reflect on the difference as energy, mineral including Ca, and vitamin intake. However, the protein content in the diet had a significant effect on urinary Ca excretion in all three feeding methods. In addition, it was clear that the intake of protein and oil affected kidney calcification in all three feeding methods. The AIN Experimental Diet Committee reported that kidney calcification was found among rats that were fed the AIN-76 diet and that one of the causes of kidney calcification was the Ca/P ratio in this diet. The protein and oil contents in the diets had significant effects on the degree of kidney calcification among rats that were fed by pair feeding or adjustable feeding. The results of this study suggest that the protein and oil contents in the diet play an important role in kidney calcification.     

The effects of consuming eggs for lunch on satiety and subsequent food intake

The aim of the present work was to investigate the effects of eggs consumed for lunch on satiety, satiation and subsequent energy intake at the next meal. Thirty-one healthy male and female subjects participated in a randomized, three-way, crossover study. Following consumption of a standard breakfast, participants were asked to consume three isocaloric test lunches: omelette, jacket potato and chicken sandwich. Subjective measures of satiety were recorded using visual analog scales at regular intervals throughout the day. Energy intake at the next meal was assessed 4 h after lunch with an ad libitum meal. The egg lunch showed a significantly stronger satiating effect compared with the jacket potato meal. No effect on energy intake was seen. These data indicate that consumption of an omelette meal consumed at lunch could increase satiety to a greater extent than a carbohydrate meal and may facilitate reduction of energy consumption between meals.     

Effect of dietary restriction on liver protein synthesis in rats

At 6 wk of age, male Fischer F344 rats were fed a purified, casein-based diet either ad libitum or in the amount of 60% of the diet consumed by the rats fed ad libitum (restricted diet). Hepatocytes were isolated from the rats between 2.5 and 19 mo of age. The protein content of the hepatocytes isolated from the rats fed the restricted amount of diet was significantly lower than that of hepatocytes isolated from rats fed ad libitum. The DNA and RNA content of the hepatocytes were similar for the rats fed the two dietary regimens. The absolute rate of protein synthesis for hepatocytes isolated from rats fed ad libitum decreased 55% between 2.5 and 19 mo of age. However, the rate of protein synthesis by hepatocytes from rats fed the restricted amount of diet decreased only slightly with increasing age. At 19 mo of age, the rate of protein synthesis by hepatocytes from the rats fed the restricted amount of diet was significantly higher than the rate of protein synthesis for hepatocytes from rats fed ad libitum. Therefore, dietary restriction retards the age-related decline in liver protein synthesis.     

Meals with similar energy densities but rich in protein,fat, carbohydrate,or alcohol have different effects on energy expenditure and substrate metabolism but not on appetite and energy intake

BACKGROUND: It has been suggested that the satiating power of the 4 macronutrients follows the oxidation hierarchy: alcohol > protein > carbohydrate > fat. However, the experimental evidence for this is still scarce. OBJECTIVE: The goal was to investigate the effects on appetite, energy intake and expenditure, and substrate metabolism of meals rich in 1 of the 4 macronutrients. DESIGN: Subjective appetite sensations, ad libitum food intake, energy expenditure, substrate metabolism, and hormone concentrations were measured for 5 h after breakfast meals with similar energy density and fiber contents but rich in either protein (32% of energy), carbohydrate (65% of energy), fat (65% of energy), or alcohol (23% of energy). Subjects were normal-weight, healthy women (n = 9) and men (n = 10) studied in a crossover design. RESULTS: There were no significant differences in hunger or satiety sensations or in ad libitum energy intake after the 4 meals. Diet-induced thermogenesis was larger after the alcohol meal (by 27%; P < 0.01), whereas protein produced an intermediary response (17%; NS) compared with carbohydrate and fat (meal effect: P < 0.01). After the alcohol meal, fat oxidation and leptin concentrations were greatly suppressed (meal effects, P < 0.0001 and P < 0.05) and triacylglycerol concentrations were as high as after the fat meal. CONCLUSION: Intake of an alcohol-rich meal stimulates energy expenditure but suppresses fat oxidation and leptin more than do isoenergetically dense meals rich in protein, carbohydrate, or fat. Despite differences in substrate metabolism and hormone concentrations, satiety and ad libitum energy intake were not significantly different between meals. Our data, therefore, do not support the proposed relation between the macronutrient oxidation hierarchy and the satiety hierarchy.     

The effect of forage quality and level of feeding on digestibility and gastrointestinal transit time of oat straw and alfalfa given to ponies and donkeys

Four donkeys and four ponies were fed molassed dehydrated alfalfa or oat straw, either ad libitum or restricted to about 70% ad libitum intake in a Latin-square design for four periods of 21 d. Measurements of apparent digestibility and gastrointestinal transit time were made on the last 7 d of each period. When the forages were provided ad libitum, all animals ate significantly more of the alfalfa than of the oat straw. Ponies consumed significantly more of both diets per unit live weight than donkeys. Higher apparent digestibilities of dietary DM, energy and fibre fractions were seen in donkeys, at both levels of feeding, compared with the ponies. This partly compensated for the lower intakes by the donkeys when fed ad libitum. When intake of alfalfa was restricted, the apparent digestibility of DM was higher compared with the corresponding values when fed ad libitum, but the reverse was true for straw. This may be because restriction of a low-quality diet reduced selection of the more digestible parts of the forage. Donkeys and ponies consumed more energy and protein than required when fed alfalfa ad libitum. Both oat straw treatments provided insufficient protein to meet the predicted requirements of ponies and donkeys. Straw intakes ad libitum exceeded the estimated energy requirement for ponies by 34-51%, but donkey energy requirements were only just met. When the amount of straw offered was restricted, 78-90% of the estimated energy requirement for donkeys was met compared with 90-105% for the ponies.     

Metabolic rate and thyroid status in rats fed diets of different protein-energy value: the importance of free T3

Oxygen consumption and thyroid hormone status have been investigated in relation to dietary protein and energy intake in young growing rats fed a control diet of 18% protein as well as diets containing 9 and 4.5% protein fed ad libitum and an 18% protein diet fed at a restricted intake for up to 14 days. Measurements of growth rate, food intake and oxygen consumption indicated that the rats fed a 4.5% protein diet ad libitum and those fed restricted amounts of an 18% protein diet have behaved similarly with severely arrested growth and reduced rates of oxygen consumption and food intake. However, the rats fed the 9% protein diet ad libitum differed from the control group only in terms of a reduced growth rate. Among all the rats thyroid hormone status was associated with the metabolic rate only in the case of the concentration of free L-3,3',5-triiodothyronine (T3), which was reduced in the groups fed 4.5% protein and 18% protein (restricted). Total T3 was actually increased in the rats fed 9% and 4.5% protein and unchanged in the restricted group. These differences in the concentrations of free and total T3 appeared to reflect the fact that the binding capacity for T3 increased with decreasing levels of dietary protein. It is concluded therefore that measurement of free rather than total T3 is the appropriate index of physiological thyroid status in protein-energy malnutrition, at least in the rat.     

Soup preloads in a variety of forms reduce meal energy intake

Consuming soup can enhance satiety and reduce energy intake. Little is known about the influence on energy intake and satiety of varying the form of soup by altering the blending of ingredients. We tested the effects on meal intake of consuming different forms of soup as a preload: broth and vegetables served separately, chunky vegetable soup, chunky-pureed vegetable soup, or pureed vegetable soup. Normal-weight men and women (n = 60) came to the laboratory for lunch once a week for 5 weeks. Each week, one of four compulsory preloads, or no preload, was consumed prior to lunch. A test meal was consumed ad libitum 15 min after the soup was served. Results showed that consuming soup significantly reduced test meal intake and total meal energy intake (preload + test meal) compared to having no soup. When soup was consumed, subjects reduced meal energy intake by 20% (134+/-25 kcal; 561+/-105 kJ). The type of soup had no significant effect on test meal intake or total meal energy intake. Consuming a preload of low-energy-dense soup, in a variety of forms, is one strategy for moderating energy intake in adults.     

A protein-rich beverage consumed as a breakfast meal leads to weaker appetitive and dietary responses v. a protein-rich solid breakfast meal in adolescents

The purpose of the present study was to determine whether a protein-rich beverage leads to a differential response in appetite, satiety and subsequent energy intake compared with an energy- and macronutrient-matched solid version in young people. A total of fifteen adolescents (eight girls and seven boys; age 14 (SEM 1) years, BMI percentile 79 (SEM 4) %) randomly completed two testing days that included protein-rich (PR) breakfast meals (38 % of energy as protein, 48 (SEM 2) g/meal) provided as a solid (S) or beverage (B). Breakfast was 24 % of estimated daily energy needs (2146 (SEM 96) kJ/meal). Perceived appetite and satiety responses were collected over 5 h followed by an ad libitum lunch buffet. The PR-S meal led to greater reductions in 4 h postprandial appetite (- 6221 (SEM 1171) mm × 240 min) v. the PR-B meal (- 3570 (SEM 957) mm × 240 min; P < 0·05). When examining the data according to hourly responses, the PR-S meal led to greater reductions in appetite during postprandial hours 2, 3 and 4 v. the PR-B meal (all comparisons, P < 0·05). No differences in postprandial hourly or total (4 h) fullness were observed following the PR-S v. PR-B meals. The PR-S meal led to approximately 480 kJ less energy consumed at the ad libitum lunch buffet (1418 (SEM 222) kJ) v. the PR-B meal (1900 (SEM 326) kJ; P < 0·05). These data indicate that, although the food form of the PR breakfast meals had little, if any, effect on satiety, the appetitive responses were diminished and the subsequent food intake was greater when protein was consumed as a beverage v. a solid meal.     

Value of serum transthyretin measurements in the assessment of marginal protein-energy malnutrition in rats

The influence of a wide range of protein and/or energy intakes on the serum level of rat transthyretin was studied. Young and adult rats were fed ad libitum diets containing 18, 9, 6, 4 and 0.5% protein (wt/wt) or were fed a control diet in restricted amounts. The transthyretin level was lower in young rats and was normal or slightly higher in adult rats fed low protein diets than in those fed the 18% protein diet. It was decreased with decreasing energy intake in all energy-restricted rats. Moderate energy restriction in rats fed equivalent amounts of protein also lowered the transthyretin level. Rats with similar body weights and similar protein intakes showed marked differences in serum transthyretin level, depending on the amount of energy consumed. Serum transthyretin changes were discussed in relation to the level of transthyretin in cerebrospinal fluid and to the serum concentration of albumin, transferrin and thyroid hormones. The results show that serum transthyretin is more closely related to the protein and energy intakes than to the protein and energy content of the diet. Our results indicate that serum transthyretin measurement is a reliable marker in the detection of early moderate and severe protein-energy restriction.     

Appetite is not influenced by a unique milk peptide: caseinomacropeptide (CMP)

The milk protein, caseinomacropeptide (CMP), is a predominant breakdown product of casein in the human stomach, and may aid in the regulation of food intake. Using a human feeding study design, this project assessed the effects of CMP on satiety and satiation by measuring the amount of food consumed at meal times and through subjective motivation to eat questionnaires. The following beverage treatments were prepared: 0.4% CMP solution, 2.0% CMP solution, vehicle alone, and water containing colorant and clouding agent. Twenty male and 32 female adults were enrolled into the study using a Latin Square randomization. Treatment beverages and ad libitum lunches were consumed on four separate occasions at the Study Center. After lunch, subjects left the Study Center, and completed a standardized questionnaire every hour throughout the afternoon and evening to assess hunger and stomach fullness, and kept track of all food and beverages consumed. Under these experimental conditions, CMP had no effect on energy intake or weight of food consumed at lunch or for the remainder of the day. CMP also had no effect on subjective indicators of satiety. Intake of CMP before a midday meal has no effect on regulation of food intake over a short-term period.     

Thyroid and growth responses of young Zucker obese and lean rats to a low protein-high carbohydrate diet

Experiments were conducted to study the effects of a low protein-high carbohydrate diet on growth and thyroid function in obese and lean male and female Zucker rats. The nine feeding regimens included animals ad libitum fed either a 22% casein and 59% carbohydrate diet (control) or an 8% casein and 73% carbohydrate diet (low protein) and appropriate pair-fed groups to control for the lean rats eating less than the obese rats and the rats fed the low-protein diet eating less than those fed the control diet. The rats were 4 weeks old at the start of the experiment which lasted 7 weeks. Final body size, tibia length and nonfat dry mass of the lean rats were dependent primarily on the amount of protein consumed, whereas growth of the obese rats was related to total energy intake rather than to protein intake. The relative hyperphagia, decreased efficiency of energy utilization and increased oxygen consumption and serum T3 concentrations in the lean rats fed the low-protein diet were consistent with the development of an adaptive thermogenesis, allowing the excess non-protein energy to be dissipated through excess heat production. There was no evidence for such an adaptive thermogenesis in the obese rats. The suggestion that the obese rats were already overeating for protein and storing the excess energy as fat and that the decreased thyroid response might be part of a protective mechanism against overheating was discussed.     

High-protein diets containing different milk protein fractions differently influence energy intake and adiposity in the rat

This study was designed to determine whether (1) protein type and (2) the dietary carbohydrate to lipid content affected daily energy intake, body weight and adiposity in rats receiving high-protein diets ad libitum over a 25 d period. Each of the ten groups (n 8) consumed ad libitum one of the diets described below. A normal protein diet (P14C56L30, containing whole milk protein) and nine high-protein diets were used. The composition of the high-protein diets varied in terms of two parameters: macronutrient composition and protein type. Three macronutrient compositions (P55C35L10, P55C15L30 and P55L45) combined with three protein types (Milk, Whey and betaLac) allowed us to test nine diets. The results show that both protein type (betaLac > Whey > Milk) and the carbohydrate to lipid ratio (P55L45>P55C35L10 or P55C15L30) modulated reductions in energy intake, body weight and adiposity in rats receiving high-protein diets ad libitum, when compared with rats fed a normal diet under the same conditions. By contrast, blood lipid profiles were mainly influenced by the carbohydrate to lipid ratio (P55C15L30>P55L45 or P55C35L10). Moreover, betaLac protein was also the most efficient in tending to preserve lean body mass at the expense of fat mass, and improve blood metabolism hormones (insulin, leptin). Taken together, the present results show that whey-derived protein sources, and particularly beta-lactoglobulin-enriched fraction, are of considerable value because of their ability to reduce both body weight gain and the adiposity index.     

Short-term effects of a snack including dried prunes on energy intake and satiety in normal-weight individuals

The purpose of this study was to test the hypothesis that a preload including dried prunes consumed as a snack before a meal, compared to an isoenergetic and equal weighed bread product preload would: (a) have greater short-term effect on satiety measured by subsequent ad libitum meal intake, (b) induce greater satiety as assessed by visual analogue scales (VAS), and (c) reduce appetite for dessert offered shortly after lunch.Forty-five healthy, normal-weight subjects participated in this randomised within-subject crossover study. Statistical analysis of the results showed that when subjects consumed the preload that included dried prunes, also consumed less amount of dessert and had lower total energy intake at meal. Additionally, subjects' feeling of hunger, desire and motivation to eat, as assessed with the use of VAS, were lower at all time points between snack and meal. Since macronutrients content of both preloads were similar, the satiating power of prunes could be due to their relatively high fiber content.Identifying meal patterns and foods that promote satiety without increasing considerably the overall energy intake is very important. The addition of dried prunes to a snack seems to promote satiety besides providing valuable nutrients.     

Increasing the protein content of meals and its effect on daily energy intake

High-protein preloads have been shown to enhance satiety, but little is known about the satiating effects of protein in more typical situations when meals are consumed ad libitum. To investigate the effects of protein in amounts commonly consumed over a day, a crossover study was conducted in 2008. In this experiment, 18 normal-weight women consumed ad libitum lunch and dinner entrées 1 day a week that were covertly varied in protein content (10%, 15%, 20%, 25%, or 30% energy). Entrées were manipulated by substituting animal protein for starchy ingredients and were matched for energy density, fat content, palatability, and appearance. Unmanipulated breakfasts and evening snacks were consumed ad libitum. Participants rated their hunger and fullness before and after meals as well as the taste and appearance of entrées. Data were analyzed using a mixed linear model. Results showed that mean 24-hour protein intake increased significantly across conditions, from 44±2 g/day in the 10% protein condition to 82±6 g/day in the 30% condition. Daily energy intake did not differ significantly across the 10% to 30% protein conditions (means 1,870±93, 1,887±93, 1,848±111, 1,876±100, and 1,807±98 kcal in the 10%, 15%, 20%, 25%, and 30% energy groups, respectively). There were no significant differences in hunger and fullness ratings across conditions or in taste and appearance ratings of the manipulated entrées. This study showed that varying the protein content of several entrées consumed ad libitum did not differentially influence daily energy intake or affect ratings of satiety.     

Effect of time of consumption of preloads on measures of satiety in healthy normal weight women

Differences in the time interval between preload and test meal may account for the variation in the satiating effects of whey protein found in previous preload studies. The objective was to compare the satiating effects (ad libitum meal intake at a set time after ingestion of preload) of whey protein (including glycomacropeptide) and maltodextrin carbohydrate and to determine whether such effects were influenced by the timing of preloads. On nine separate days, 19 healthy normal weight women consumed mixed composition preloads containing either water, or maltodextrin, or whey protein, 30, 60 or 120min before an ad libitum test meal. Whey protein reduced food intake (p<0.05) at the test meal more than maltodextrin and water (respective food energy intakes were 2343, 2584 and 3135kJ). The time interval between preload and test meal did not affect the food intake response. Total energy intake (preload+test meal) differed, with intake for the maltodextrin-enriched preload being greater than that for the whey protein-enriched preload, which was greater than for the water control. Total respective energy intakes were 3955, 3676 and 3135kJ. Subjective ratings of appetite did not support a greater satiating effect of whey protein versus maltodextrin on food intake but there was evidence for a satiating effect of maltodextrin and whey protein versus the water control.