Effects of scheduled food and water deprivation on food intake, water intake and body weight of cage-adapted and cage-naive rats

The first experiment examined the effects of four food-deprivation schedules and four water-deprivation schedules on body weight, food intake and water intake of adult rats over ten days of deprivation and two days of recovery. During food deprivation, water intake was gradually reduced. During water deprivation, daily food intake was initially depressed but eventually returned to ad libitum levels. Consumption of restricted commodities increased over the deprivation phase. Experiment 2 showed that mutual deprivation of food and water are more apparent in rats not previously adapted to the test environment and the final experiment indicated that this was due to the inexperience of cage-naive rats in feeding under novel conditions. The results are evaluated in relation to the environmental factors that may play as great a role as physiological processes in regulating the feeding/drinking behaviour of laboratory rats.     

Effects of changes in palatability on food intake and the cumulative food intake curve in man

This study was undertaken to quantify the relationship between palatability ratings and food consumption and to determine whether the initial rate of eating was affected by changes in food palatability without a change in nutrient content. Both men and women were given small samples of foods at a brief exposure taste test and asked to rate how much they liked or disliked them on a 9-point scale (like extremely to dislike extremely). Those who gave at least a 2-point difference in rating between a banana colada frozen yogurt drink with and without adulteration with cumin were given these foods to eat to satiety on non-consecutive days, and the same 9-point scale was used to rate these foods after they had been eaten as meals. Cumin was used as an adulterant because it is not intrinsically unpalatable, but is not liked by many individuals in yogurt-based foods. Intake was approximately 100 g different for every unit of difference on the scale, and higher for liked than disliked food. Intake was significantly different between the adulterated and unadulterated meals. The percentage of variance explained by the difference in palatability was 34% of the total variance but was 67% of the variance within subjects. Correlation between intake and ratings were poor across subjects for both palatability levels (i.e. adulterated and unadulterated). The initial rate of eating was significantly higher under the better liked than under the less liked food. These results indicate that quantification of effects of hedonic ratings on intake within subjects is possible, but that hedonic ratings may not be good discriminators of intake differences between subjects. The initial rate of eating reflects partly on palatability.     

Interdependency of food and water intake in humans

The temporal and quantitative relationship between food and water intake and the effect of fluid restriction on voluntary food intake were studied in 20 male subjects over two 48-h periods. Food intake was limited to specific mealtimes, but subjects could eat as much as they wanted during these times. Drinking was ad libitum in one condition, and limited by about 40% of ad libitum drinking in the other condition. Approximately 68% of all drinking occurred when food was available at mealtimes when drinking was ad libitum. When fluid intake was limited, subjects voluntarily reduced their food intake. Food acceptability, as measured by hedonic ratings, was not significantly affected by fluid restriction even though food intake was significantly reduced. The intensity rating of thirst was negatively correlated with food intake. Indirect comparisons are drawn with eating and drinking relationships in non-human species.     

The effects of dietary lead content and food restriction on lead retention in rats

The effects of restricted food intake and of various dietary lead contents on lead retention¹ were studied in young rats. In three experiments the rats were given either unrestricted or restricted access to diets providing 200 or 400 mg lead/kg for 3 or 6 weeks. At the end of the experiments a sample of blood was taken and the rats were ashed. Lead was determined in blood and ash from the carcass. Food restriction always increased the retention of lead but not always the lead content of blood or carcass. The retention of lead was similar when the diet was supplemented with 50, 200 or 400 mg lead/kg. Lead supplementation at 200 or 400 mg/kg reduced food intake and growth but did not affect food conversion ratios. Blood lead was related to the rate of ingestion of lead. The effect of food restriction in reducing lead retention should be taken into account in interpreting the effects of lead exposure accompanied by dietary conditions which reduce appetite or food supply.     

Endorphinergic mechanisms in the control of food and water intake

The recent discovery of opiate receptors and endogenous opiates (endorphins) within the brain has led to a variety of speculations concerning the physiological significance of these mechanisms. One suggestion has been that endorphinergic mechanisms may be involved in the control of food and water intake. Administration of drugs believed to block opiate receptors has been shown to reduce food and water intake in experimental animals while opiate agonist drugs can, under certain conditions, increase eating and drinking. It has also been shown that endorphin levels in the brain and pituitary may change with food deprivation and in obese animals. The evidence is therefore consistent with a role for endorphins in the control of appetite. However, it will be for future research to define more precisely the nature of the mechanisms involved.     

Effects of physical activity on food intake

The understanding of the effect of physical activity (PA) on food intake is imperative for considering PA as an additional tool for prevention and treatment of many diseases. Prolonged strenuous PA performed on a regular basis causes an increase in overall energy turnover, and leads either to loss of body weight, or to an increased food intake. When leading to loss of body weight, PA may be used as a therapeutic adjunct in the treatment of obesity. When increasing food intake to compensate for increased energy expenditure and maintaining body weight, PA, by increasing intake of other constituents of food like minerals and vitamins, may contribute to micronutrient deficiency coverage. However, the type of activity, as well as body composition of the individuals engaging in sport, play an important role in food intake regulation and its changes with time. Some studies indicate that short-term exercise does not have the same effect on food intake as long-term exercise and that eventual increase in food intake due to increased PA does not follow the same pattern in obese as in lean individuals. To better understand the relationship between PA on food intake, current findings on this topic will be summarized in this paper.     

Genetic differences in effects of food restriction on aging in mice

Lifelong food restriction to two-thirds of normal ad libitum consumption extended mean and maximum life spans more than 200 d in male B6CBAF1 hybrid mice, already a long-lived genotype. The following biological systems were improved by food restriction, with values for older mice being similar to those previously found for younger individuals: tight wire clinging, a measure of neuromuscular performance; open field movement, a measure of voluntary activity; tail tendon denaturation rate, a measure of collagen solubility; urine concentrating ability, a measure of renal function, and hair regrowth rate, a measure of the frequency of hair follicle cycling. However, wound healing was slower in food-restricted mice than in ad libitum-fed controls. The same food restriction treatment had entirely different effects on longevities of a different genotype, male B6 (C57BL/6J) mice, reducing mean and maximum life spans 265 and 27 d, respectively. This surprising deleterious effect was not predicted by tests of tight wire clinging, open field movement and tail tendon denaturation, but was predicted by hair regrowth rates, as these were lower in restricted B6 mice than in fed controls. In genetically obese (ob/ob) B6 mice, food restriction extended mean and maximum longevities 327 and 440 d, yet no biological systems tested performed better than those of food-restricted normal (+/+) mice whose life spans were reduced. Thus the food restriction regimen that increased longevities for individuals of two genotypes decreased them for individuals of a third genotype tested in the same set of experiments.     

Selective carbohydrate or protein restriction: effects on subsequent food intake and cravings

In order to determine the effects of selective food restriction on subsequent food intake and cravings, participants were randomly assigned to one of three conditions: carbohydrate-restriction, protein-restriction, or control (no restriction). Participants in the restriction conditions were asked to restrict their intake of either complex carbohydrates or animal proteins for 3 days, before coming to the laboratory for an experimental session. During the experimental session, participants' food intake, cravings, and affect were measured. The results indicated that selective food restriction resulted in selective behavioural consequences. Specifically, carbohydrate-restricted participants consumed more of a high-carbohydrate food than did controls or protein-restrictors, in addition to reporting more cravings for high-carbohydrate foods over the restriction period. Protein-restricted participants reported more cravings for high-protein foods over the restriction period, in comparison to controls and carbohydrate-restrictors; however, protein-restricted participants did not consume more of the particular high-protein food presented to them in the laboratory. The roles of dietary restraint and negative affect in influencing cravings and food intake are discussed. Overall, selective food restriction is demonstrated to have negative psychological and behavioural consequences.     

双酚A对成年雄性小鼠体质量、摄食和肝功能的影响

目的 探讨双酚A对成年雄性小鼠体质量、摄食和肝功能的影响.方法 100只成年雄性ICR小鼠随机分为阴性对照组、己烯雌酚对照组、双酚A 2、20、100 mg/kg组,各组动物用相应受试物连续灌胃2周,于第8周将小鼠处死.用酶化学方法检测丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、γ-谷氨酞基转移酶(GG...     

Effects of caloric manipulations on food intake in baboons

Food intake of seven adult male baboons (Papio cynocephalus anubis) was monitored during daily 22-h experimental sessions. Food was available under a two-component operant schedule. Following completion of the first "procurement component" response requirement, access to food, i.e. a meal, became available under the second "consumption component," during which each response produced a 1-g food pellet. After a 10-min interval in which no response occurred, the consumption component was terminated. The effects of caloric preloads on food intake were determined by giving each baboon a meal of preferred foods 45-60 min prior to the start of the daily session. Caloric preloads decreased food intake during the first 8 h of the session, but had no effect on intake during the entire session. The effects of acute deprivation on food intake were determined by terminating sessions after a baboon had consumed 20-80% of baseline intake, and by starting a session 4-12 h late. Deprivation did not increase subsequent food intake. The effects of the availability of an alternative source of calories on total daily intake were determined by providing access to a dextrose solution. Baboons decreased intake of solid food in accordance with the caloric intake from the dextrose solutions by decreasing the number of meals. Finally, the effects of providing a diet of higher caloric density on food intake were determined. Two of the four baboons tested in this procedure maintained baseline levels of daily caloric intake, while the other two baboons increased daily caloric intake. In summary, free-feeding baboons were relatively insensitive to acute changes in feeding conditions, but were sensitive to long-term changes in the caloric content of available foods.     

Effects of xylitol on gastric emptying and food intake

We studied the effects of xylitol, the pentose-sugar alcohol, on gastric emptying of the solid-food component of a complex meal. Gastric emptying was measured in human volunteers by utilizing a standardized radiolabeled scrambled-egg meal. After ingestion of 25 g xylitol, gastric emptying was markedly prolonged (T-1/2 58 +/- 5 min control vs 91 +/- 7 min after xylitol [p less than 0.01]). Since delayed gastric emptying may affect food intake, we evaluated the effects of xylitol on calorie intake. Food intake after oral preloading with water resulted in intake of 920 +/- 60 kcal vs 690 +/- 45 kcal after 25 g of xylitol. In contrast, a preload of glucose, fructose, or sucrose failed to suppress food intake. Although xylitol decreased food intake and also delayed gastric emptying, these effects may be unrelated. Our data suggest a role for xylitol as a potentially important agent in dietary control.     

饮食限制对小鼠学习记忆及抗氧化能力影响

目的探讨不同饮食限制(dietary restriction,DR)水平对小鼠学习记忆、抗氧化能力影响。方法120只ICR小鼠随机分为自由饮食(对照)组,20%,40%,60%DR组,连续25 d,进行力竭游泳及耐缺氧实验;39 d后,进行Y迷宫、水迷宫、脏器系数、超氧化物歧化酶(SOD)及丙二醛(MDA)含量的测定。结果Y迷宫结果表明,40%DR组记忆成绩(14.40±2.68)次,与自由饮食组比较差异有统计学意义(P0.05);水迷宫结果表明,40%DR组潜伏期(20.36±9.12)s,访问次数(1.5±0.5)次,游动距离(0.49±0.32)m。;60%DR组脑系数为(1.51±0.19)%,明显高于自由饮食组(1.12±0.09)%(P0.01);各饮食限制组小鼠脾脏、甲状腺系数及肾脏丙二醛(MDA)含量均有所下降;小鼠耐力及耐缺氧能力与限制水平成正比,雌鼠耐缺氧能力强于雄鼠。结论适当饮食限制可以提高机体对新环境适应能力,提高体内抗氧化系统活性。     

Effects of exercise intensity on food intake and appetite in women

BACKGROUND: Increasing exercise intensity has been shown to reduce energy intake in men. OBJECTIVE: The main objective of this study was to investigate the effects of exercise intensity on energy intake in women. DESIGN: Thirteen moderately active (peak oxygen uptake: 44.0 +/- 4.7 mL . kg(-1) . min(-1)) women [body mass index (in kg/m(2)): 22.2 +/- 2.4; age: 22.2 +/- 2.0 y] were subjected to 3 experimental conditions: control with no exercise and 2 equicaloric (350 kcal) low- (LIE) and high- (HIE) intensity exercise sessions at 40% and 70% of peak oxygen uptake, respectively. After each session, the participants ate ad libitum from buffet-type meals at lunch and dinner and ate snacks during the afternoon and evening. Visual analogue scales were used to rate appetite. RESULTS: More energy was ingested at lunchtime after the HIE session than after the control session (878 +/- 309 and 751 +/- 230 kcal, respectively; P = 0.02). Relative energy intake (postexercise energy intake corrected for the energy cost of exercise above the resting level) at lunch was lower after the LIE session than after the control session (530 +/- 233 and 751 +/- 230 kcal, respectively; P < 0.001) and was lower after the HIE session than after the control session (565 +/- 301 and 751 +/- 230 kcal, respectively; P < 0.01). Similarly, daily energy intake tended to increase during the HIE session relative to that during the control session. No treatment effect was found for appetite scores throughout the experiment. CONCLUSION: The results suggest that HIE increases energy intake in women.     

Effects of fructose and glucose preloads on subsequent food intake

To determine how the nutrient content of one eating event might affect amount consumed at the next, we evaluated whether equicaloric fructose and glucose preloads differentially influence subsequent food intake. Subjects consumed 50 g of glucose or fructose in 500 ml of water or water alone and were given a "buffet" containing a variety of foods two and a quarter hours later. Subjects in glucose conditions ate, on the average, 252 X 7 calories more than subjects in the water condition, who in turn ate, on the average, 225 X 9 calories more than subjects in the fructose condition. The fructose and glucose preloads did not differentially affect the amount eaten of different types of nutrients (carbohydrate, fat and protein). This study, employing several sensory and cognitive controls, suggests that type of nutrient ingested, in and of itself, plays a role in determining subsequent intake for humans. The data are discussed in terms of possible physiological mechanisms that might account for these effects.