Effects of aldosterone and deoxycorticosterone on food intake and body weight

Aldosterone (.25 mg/kg) or deoxycorticosterone (3 mg/kg) in combination with corticosterone was administered daily to female adrenalectomized rats. The mineralocorticoids increased food intake and weight gain well beyond that of controls receiving only corticosterone injections. The weight gain was not wholly dependent on increased food intake, as separate groups of animals maintained on a restricted (10 g of laboratory chow/day) diet also displayed significant mineralocorticoid-stimulated weight gain. Although carcass composition was not directly determined, the undifferentiated wet/dry tissue ratios, hematocrit values, and nasoanal lengths found across groups suggest that the observed effect of mineralocorticoids was on body fat. Aldosterone and deoxycorticosterone can have important actions on energy metabolism as well as on sodium regulation.     

Long term effects of quinine on food intake and body weight in the rat

Adulteration of a chow diet with 0.75% quinine sulfate produces a short-lived decrement in food intake in both ad lib-fed and previously food-restricted adult female rats. In contrast, quinine produces a long-lasting depression in body weight; ad lib access to quinine-treated chow results in a plateauing of body weight at a lower level until quinine is removed from the diet, despite recovery of food intake.     

Sexually dimorphic effects of forced exercise on food intake and body weight in the rat

The food intake (FI), body weight (BWt) and water intake (WI) of adult male and female rats were compared during a seven day period of forced exercise in a treadmill. Work loads for the exercised groups were gradually increased across the seven-day test period, whereas work loads for the sedentary controls were maintained at the same level used during a previous three-day training period. Relative to their respective control groups, male rats showed a decrease in FI and BWt in response to the exercise challenge, but female rats showed an increase in FI sufficient to maintain their BWt at control levels. Both male and female rats showed a reliable increase in WI during the period of forced exercise. These sexually dimorphic changes in FI and BWt in response to forced exercise indicate that female rats are capable of demonstrating a more vigorous defense of BWt than are male rats and suggest that there is a sex difference in the long-term control of feeding behavior in the rat.     

Fluoxetine-maintained obese humans: effect on food intake and body weight

The effects of fluoxetine on food intake, body weight, and mood of obese individuals was examined in a 16-week inpatient/outpatient study. Six male and eight female obese volunteers began the study (four male and five females completed all phases of the study). They lived in a residential laboratory during three one-week inpatient periods separated by a 5-week and an 8-week outpatient period. Following an initial 4-day placebo baseline, participants were maintained on fluoxetine (60 mg/day) for the remainder of the study. Food intake parameters (total daily energy intake, macronutrient intake, mean number of eating bouts, interbout interval), body weight, subjective effects, and task performance were measured several times during the day during inpatient periods; food intake questionnaires were completed daily during the outpatient periods. Fluoxetine significantly reduced daily energy intake derived from fat, carbohydrate, and protein by decreasing the mean number of eating bouts per day throughout the study. No other food intake parameter was affected. Body weight was significantly reduced after 7 weeks, but not after 16 weeks of daily fluoxetine administration. These results indicate that fluoxetine reduced food intake for at least 16 weeks in nondepressed obese individuals without specifically affecting carbohydrate intake. Weight that was lost during the first few weeks of daily fluoxetine administration was subsequently regained even though food intake remained reduced. Therefore, fluoxetine maintenance does not appear promising as a sole long-term therapy for obesity.     

Signals that influence food intake and body weight

Energy homeostasis is a complex on-going process that includes maintaining immediately available as well as stored nutrient levels at optimal levels given the environment. To accomplish this, the brain receives continuous information about stored energy and current and anticipated fluxes in critical organs, as well as about food that is potentially available or being eaten and absorbed. The brain in turn determines when and how much food will be consumed, balancing this activity with other behaviors. This review discusses hormonal and related satiety signals generated as food is being consumed, and upon adiposity signals related to the amount of fat stored in the body, that influence energy intake and ultimately body weight.     

Effects of ovariectomy and estradiol on body weight and food intake in gold thioglucose-treated mice

Two experiments investigated the effects of ovariectomy and estradiol replacement on the body weight and food intake of mice that had previously been treated with either gold thioglucose or saline. Ovariectomy and estradiol benzoate injections altered food intake in gold thioglucose-treated mice as much as in saline controls. Ovariectomy increased body weight in saline controls but it was without effect on the body weight of gold thioglucose-treated mice.     

Effects of selective estrogen receptor agonists on food intake and body weight gain in rats

Ovariectomized (OVX) rats eat more and gain weight more rapidly than sham-operated (SO) rats and estradiol (E(2)) treatment attenuates food intake and body weight gain in OVX rats. Studies were designed to test the hypothesis that the alpha subtype of the estrogen receptor (ERalpha) mediates the attenuating effects of E(2) on food intake and body weight gain while the beta subtype (ERbeta) mediates opposing actions that lead to increased food intake and body weight gain. Female rats were SO or OVX and treated daily with vehicle (dimethylsulfoxide, DMSO) or E(2) (10 microg/day), or the ERalpha-selective agonist, 4,4',4'-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT, 0.5 mg/day), or the ERbeta-selective agonist, 2,3-bis(4-hyroxyphenyl)-propionitrile (DPN, 0.5 mg/day) for 14 days. Total food intake was significantly reduced by E(2) and PPT, but not DPN. Total body weight gain was significantly increased in OVX rats compared to SO rats and treatment with E(2) or PPT, but not DPN, significantly decreased total body weight gain to levels that were not significantly different from SO rats. A dose-response study of PPT indicated that at 0.25 mg/day, PPT significantly reduced total 21-day food intake and body weight gain and, at 0.13 and 0.06 mg/day, PPT significantly reduced total body weight gain compared to OVX rats without significantly reducing total food intake. A dose-response study of DPN indicated that none of the three doses of DPN significantly altered total 21-day food intake or total body weight gain. These results suggest ERalpha mediates the attenuating effects of estrogens on food intake and body weight gain while ERbeta has no effect on these variables.     

Melatonin and lighting condition: Absence of long-term effects on food intake and body weight regulation in the albino rat

In contrast to photoperiodic rodents, the nonphotoperiodic laboratory rat's food intake and body weight was unaffected by melatonin treatment (Silastic implants). Constant dark and constant light were equally ineffective as well in disturbing these regulatory behaviors.     

The effects of long warm and cold ambient exposures on food intake water intake and body weight in the capsaicin desensitized rat

Seventeen Sprague Dawley rats received, subcutaneously, 250 mg·kg^–1 of capsaicin divided into 10 increasing doses (10–50 mg·kg^–1) and administered on 7 successive days. Nine controls were treated with an isotonic saline solution using the same protocol. The rats spent, in succession, 5 weeks at 20° C, 6 weeks at 33.5° C, 6 weeks at 8° C, 4 weeks at 30° C and, finally, 5 weeks at 20° C ambient temperature. Their mean food intake (FI), water intake (WI) and body weights were recorded daily. In the 2 groups of rats, FI was inversely related to ambient temperature. However, during the first few days of the exposures, FI in treated rats was greater than controls in the warm environment and less in the cold environment. In controls, WI increased linearly with ambient temperature in the warm environment. This relation was not found in treated rats: they drank less water than controls and lost body weight. During the first days at 8° C ambient temperature, rectal temperature decreased in treated rats and two animals died.The results are similar to those described for rats with hypothalamic lesions. They may also be related to a peripheral effect of the drug.This work was supported by the Centre National de la Recherche Scientifique (C.N.R.S. L.A. 181) and by the Institut National de la Santé et de la Recherche Médicale (I.N.S.E.R.M., A.T.P. 80-79-112)     

Ovarian influences on food intake and body weight regulation in lactating rats

In the following experiments, an attempt was made to determine the role of the ovary in the control of food intake and body weight regulation during lactation. In the first study, it was found that concentrations of estradiol benzoate effective in suppressing food intake and body weight in nonlactating animals were not effective during lactation. In the second experiment, ovariectomy during lactation was shown not to produce the usual increases in food intake and body weight or change in meal patterns known to occur after ovariectomy in the nonlactating rat. These results suggested that lactating animals behave the as though functionally ovariectomized and that the removal of the ovaries is of no additional consequence. The further observation that animals nursing small litters gained weight considerably more rapidly than animals nursing large litters led to the prediction that these animals would also be more responsive to the suppressive effects of EB. In the third study, EB in concentrations which are not effective in suppressing body weight in animals nursing large litters was found to suppress body weight in mothers with small litters. However, since these animals also showed a decline in milk yield, a number of alternative interpretations of these results were considered. These results, together with data concerning levels of ovarian hormones during gestation and lactation led to the hypothesis that pregnant and lactating animals undergo an elevation in body weight set-point, similar in magnitude and quality to elevations following ovariectomy in the nonlactating animal.     

Effects of bulbectomy on hibernation,food intake and body weight in the european hamster,Cricetus cricetus

Bulbectomy was performed on European male wild hamsters in autumn, habitual phase of weight decline and entrance into hibernation. Total bulbectomy suppresses both nest building behavior and hibernation, and is followed by an immediate increase in food intake and obesity. The body weight curve of totally bulbectomized animals is in opposition of phase with that of the controls. Incomplete bulbectomy suppresses nest building behavior but hibernation is present with a diminution of periodic arousals. Hyperphagia starts in spring after the terminal arousal; it is similar to that of the total bulbectomized animals. Anosmic animals do not differ from the control animals.     

Gastric balloon reduces food intake and body weight in obese rats

A less invasive method than gastric reduction surgery for treating obesity was tested by inserting balloons into the stomachs of obese rats. Male Sprague-Dawley rats were placed on a high fat diet. After 4 months, the rats weighed an average of 750 g or 23% more than rats on a chow diet. Balloons were then passed orally into the stomach, inflated with 10 ml of water, and detached from the inflating tube. Eight rats had inflated balloons; six rats had no balloons. The balloons, which could be palpated, remained inflated for 12 to 49 days with a mean of 25 days. During the period of inflation, rats with balloons consumed significantly less food (p less than 0.001) relative to rats without balloons. Gastric emptying rate was significantly slowed (p less than 0.0025) in rats with inflated balloons compared to rats with balloons that had deflated and rats with no balloons. Histology of the stomachs that held inflated balloons did not reveal pathology.     

Effects of stereoisomers of estradiol on food intake, body weight and hoarding behavior in female rats

The effects of 17-alpha and 17-beta estradiol on food intake, body weight and hoarding behavior in ovariectomised rats were investigated. For five days, ten animals received subcutaneous injections of both isomers (10 micrograms/kg/day) in a counterbalanced design. Hoarding tests were conducted on the last three days of each 5-day injection period. 17-Alpha estradiol significantly reduced food intake but was without effect on body weight. 17-Beta estradiol reduced food intake significantly more than the alpha form and also significantly reduced body weight. These differential effects suggest that stereoisomers of estradiol may be acting on separate regulatory systems. The treatments did not change hoarding activity compared to pre-treatment levels.     

Effects of dietary dehydroepiandrosterone on food intake and body weight in rats with medial hypothalamic knife cuts

Dehydroepiandrosterone (DHEA) is a steroid which has been reported to have anti-obesity effects when added to the diets of rats and mice. In this report, rats made hyperphagic with medial hypothalamic knife cuts were placed on a diet containing 0.45% DHEA or a control diet. Knife cut rats on the control diet ate more food and gained more weight than sham-operated rats on the control diet. In contrast, knife cut rats fed the DHEA diet weighed the same as shams on the DHEA diet and were only observed to be hyperphagic on one of eight 24 hour measurements taken during a five week period. Dietary DHEA reduced food intake and body weight of both knife cut and sham-operated rats, though the effects were smaller in shams. As these effects of DHEA were reminiscent of the effects of dietary quinine adulteration on intake by knife cut rats, a second experiment measured the food intake of unoperated rats when given a choice between a control high-fat diet and one adulterated with various concentrations of DHEA. Even at a concentration of 0.05%, rats clearly identified and avoided the DHEA-adulterated diet. While these results do not rule out effects of DHEA on metabolic rate or lipogenesis, they do indicate that the unpalatability of DHEA-adulterated diets may be a contributing factor in the observed effects on food intake and body weight.     

Role of the stria terminalis in food intake and body weight in rats

Previous studies have shown that lesions of the posterodorsal amygdala result in hyperphagia and obesity in female rats. In the present study, lesions of the stria terminalis at its most dorsal point (before it separates into dorsal and ventral components) also resulted in hyperphagia and excessive weight gains in female rats compared to female rats with sham lesions, as did coronal knife cuts anterior to the ventromedial hypothalamus. Identical lesions and knife cuts did not elevate food intake or weight gains in male rats compared to male control animals. Examination of the anterograde degeneration with the amino-cupric-silver method in the brains of two female rats with hypothalamic knife cuts revealed degenerating terminals in the capsule of the ventromedial hypothalamus and in the premammillary nuclei, two classic indicators of damage to the dorsal component of the stria terminalis. No degenerating axon terminals were observed in the paraventricular nucleus. Differences from previous studies that used male rats were attributed to a sex difference for the effects of amygdaloid and ventromedial hypothalamic lesions. It is proposed that the posterodorsal amygdala, dorsal component of the stria terminalis, and ventromedial hypothalamus are part of an inhibitory pathway in the regulation of feeding behavior.     

Comparison of androgenic effects on food intake and body weight in adult rats

In order to investigate the interrelationships between sex hormones, food intake, and body weight, three androgens (testosterone propionate (TP), dihydrotestosterone (DHT), and androstenedione (ANDR)) were administered to separate groups of gonadectomized adult rats of both sexes. In males TP increased body weight to the greatest degree, while the effects of DHT, a non-aromatizable androgen, and ANDR were approximately equal to each other. The relationship between each androgen and food intake partly paralleled that of body weight. In females, however, DHT exerted a stronger effect on body weight than TP, and ANDR produced no significant increases: food intake was stimulated by both TP and DHT. As others have indicated, aromatization of testosterone to estrogen then is not critical to the effect of androgens on either food intake or body weight. Furthermore, the fact that increases in body weight are not always accompanied by concomitant changes in food intake suggests that gonadal hormones may exert their effects on body weight primarily through various metabolic processes, not simply through changes in food intake.     

Energetic limits on reproduction: Maternal food intake

We examined the factors influencing maternal food intake and pup growth in Norway rats. Mother rats allowed pups in naturally large litters to grow at a slower rate than pups in naturally small litters. Pups reared by dams in a warm ambience (26°C) gained weight more slowly than dams at 22°C, and maternal food intake but not weight gain was depressed in the high ambient temperature. Pup growth at 18°C was unimpaired, with those dams eating no more and gaining no less weight than dams at 22°C. Nest material, however, was found to be essential for the successful rearing of young at cooler ambient temperatures. While restriction of food during gestation resulted in a marginally lower weight gain for the pups during the first 2 weeks postpartum, the dams appeared not to mobilize corporal stores or increase their food intake during lactation. Heavy body weight mothers did not eat any more, nor did they gain any less weight nor rear larger pups than light body weight dams. Rat mothers increased their consumption of a diet diluted with non-nutritive fiber to equal the nutritive intake of their controls, with their pups not differing in their growth rate. Pups reared by dams eating a high quality diet grew faster than pups with dams on the control diet. Food intake by mother rats is required during lactation relative to the amount of milk that is delivered to the pups, rather than to an absolute amount of food. Lactating females with a concurrent pregnancy neither increase their food intake nor appear to mobilize their corporal stores to deal with the added energetic drain of pregnancy. Indeed, their young grew somewhat more quickly than pups nursed by dams that were simply lactating. Taken as a whole, these results suggest that Norway rat dams apparently do not monitor and defend a maximal pup growth rate. Rather, rat dams seem to continue to defend their own homeostasis, and by doing so, allow the young to grow and survive under a wide variety of circumstances.     

The effects of estradiol on body weight and food intake in normal weight VMH-lesioned rats.

The effects of estradiol on food intake and body weight were examined in ovariectomized and VMH-lesioned, ovariectomized rats that were prevented from supranormal weight gain by food restriction. Estradiol injections that were effective in reducing weight in supranormal weight, ovariectomized rats had no effect on weight in normal weight, ovariectomized or VMH-lesioned, ovariectomized rats. Estradiol did not prevent hyperphagia and weight gain in VMH-lesioned, ovariectomized rats when they were provided with ad lib food.     

Chronic intrahypothalamic infusions of insulin or insulin antibodies alter body weight and food intake in the rat.

In Experiment 1, one-week infusion of insulin (0.15, 1.5, or 15.0 microU/hr) into the ventromedial hypothalamus (VMH) of rats reduced body weight (BW) and nighttime food intake (FI). While 0.15 microU/h decreased daytime FI, 1.5 microU/h increased daytime FI and 15.0 microU/h left daytime FI unchanged. Total daily FI was decreased by the two highest doses. In Experiment 2, intra-VMH infusion of specific insulin antibodies (1.5 microUeq/h) increased BW and FI, while C-peptide antibodies were ineffective. In Experiment 3a, intracerebroventricular infusions of insulin failed to decrease FI and BW comparably to similar intrahypothalamic infusions. In Experiment 3b, intra-VMH insulin was infused via cannulae that bypassed the cerebral ventricles. The decrease in FI and BW was comparable to that observed when insulin was infused via cannulae that penetrated a ventricle. Histology from animals used in Experiments 1-3 indicates that optimum sites for insulin-induced changes in BW and FI in the hypothalamus lie in an area that includes portions of the paraventricular, arcuate, dorsomedial, and ventromedial nuclei.     

Relation between estrogen-induced hyperlipemia and food intake and body weight in rats

Thirteen experiments on 348 ovariectomized female rats examined the relationship between estradiol's effects on food intake and body weight and on plasma triglycerides, free glycerol, and fatty acids. The time course of estradiol benzoate effects on food intake and weight gain differed from the time course of triglyceride elevation. The antiestrogen, nafoxidine, given with estradiol blocked the hypertriglyceridemia, but not the weight loss, resulting from estradiol benzoate. Estradiol benzoate treatment for up to three days had no significant effect on plasma triglyceride levels following intragastric and intravenous triglyceride administration. Changes in plasma triglyceride following Triton WR-1339 indicated that the absolute rates of plasma triglyceride clearance were not impaired by estradiol. These results contradict Wade and Gray's [31] hypothesis about the mechanism of estradiol-induced hypophagia.