Meal Patterns Of Rats Research Articles

Lingual Taste Nerve Transection Alters Food Selection, Relative Macronutrient Intake, and Meal Patterns in Rats Consuming a Cafeteria Diet without Changing Total Energy Intake.

The control of ingestive behavior is complex and involves input from many different sources, including the gustatory system. Signals transmitted via the taste nerves trigger responses that promote or discourage ingestion. The lingual taste nerves innervate 70% of taste buds, yet their role in the control of food selection and intake remarkably remains relatively underinvestigated. Here we used our custom five-item Food Choice Monitor to compare postsurgical behavioral responses to chow and a five-choice cafeteria diet (CAF) between male rats that had sham surgery (SHAM) or histologically verified transection of the chorda tympani and glossopharyngeal nerves (2NX). Compared with SHAM rats, 2NX rats ate significantly more of the high-fat CAF foods. The altered food choices led to dramatically increased fat intake and substantially reduced carbohydrate intake by 2NX vs SHAM rats. Furthermore, whether offered chow or CAF, 2NX rats ate fewer, larger meals each day. Eating rates implied that, compared with SHAM, 2NX rats were equally motivated to consume CAF but less motivated to eat chow. Even with these differences, energy intake and weight gain trajectories remained similar between SHAM and 2NX rats. Although some rats experienced CAF before surgery, contrary to our expectations, the effects of prior CAF experience on postsurgical eating were minimal. In conclusion, although total energy intake was unaffected, our results clearly indicate that information from one or both lingual taste nerves has a critical role in food selection, regulation of macronutrient intake, and meal termination but not long-term energy balance.

A new apparatus to analyze meal-related ingestive behaviors in rats fed a complex multi-food diet

The measurement of the size and timing of meals provides critical insight into the processes underlying food intake. While most work has been conducted with a single food or fluid, the availability of food choices can also influence eating and interact with these processes. The 5-Item Food Choice Monitor (FCM), a device that continuously measures eating and drinking behaviors of rats provided up to 5 foods and 2 fluids simultaneously, was designed to allow study of food choices simultaneously with meal patterns. To validate this device, adult male and female (n = 8 each) Sprague-Dawley rats were housed in the FCM. Food and fluid intake were measured continuously (22-h/day) while rats were presented water and powdered chow. Then a cafeteria diet of 5 foods varying in macronutrient content, texture, and flavors were offered along with water. Lastly, the 5 foods were offered along with 0.3 M sucrose and water. Analyses were conducted to find optimal criteria for parceling ingestive behavior into meals, and then meal patterns were quantified. Total intake, as assessed by FCM software, was in good concordance with that measured by an independent scale. A minimum meal size of 1 kcal and a meal termination criterion of 15-min accounted for >90% of total intake and produced meal dynamics that were in register with the literature. Use of the cafeteria diet allowed comparisons between meal patterns with a single food versus a multi-food diet, as well as analyses of macronutrient-related food choices across subsets of meals. The FCM proved to accurately measure food intake over a 22-h period and was able to detect differences and similarities in the meal patterns of rats as a function of sex and food choice availability. Combined with any number of experimental manipulations, the FCM holds great promise in the investigation of the physiological and neural controls of ingestive behavior in a dietary environment that allows food choices, more closely emulating human eating conditions.

Sex and individual differences in meal patterns mediate the persistency of running-associated high-fat diet avoidance in rats.

The modern environment is characterized by convenient access to a variety of high-fat (HF) foods and encourages excess energy intake, which leads to weight gain. While healthier diets and exercise are common interventions that facilitate energy balance, meal patterns also influence body weight and energy metabolism. The current study characterized the association among exercise, diet choice, and meal patterns in rats. Unlike sedentary rats, which prefer a HF to a chow diet, wheel-running rats initially avoid the HF diet. Subsequently, the running-induced HF diet avoidance persists longer in males than in females. We hypothesized that differences in meal patterns contribute to sex differences in the prevalence and persistency of HF diet avoidance. During two-diet choice, rats did not mix chow and HF diet within a meal and consumed discrete meals of each diet. Exercise decreased chow meal size in both sexes (4.5 vs. 5.7 kcal) but decreased total meal frequency only in male rats. Analyses of individual differences revealed WR rats that maintained HF diet avoidance (HF avoiders) had larger chow than HF meals (5.2 vs. 1.3 kcal) upon initial 3 days of diet choice. When compared with rats that reversed HF avoidance (HF eaters), HF avoiders had shorter latency to consume their first meal of HF diet (2.6 vs. 98.9 min) upon initial running and diet choice. Taken together, these results suggest that both sex and individual differences in meal patterns contribute to differences in the persistency of exercise-associated HF diet avoidance.

Effects of isolated tobacco alkaloids and tobacco products on deprivation-induced food intake and meal patterns in rats

The ability of smoking to reduce body weight serves as motivation for continued smoking. It is unclear to what extent non-nicotine constituents in cigarettes are contributing to the weight-reducing effect of smoking. The purpose of the current study was to examine the effects of nicotine and four minor tobacco alkaloids (nornicotine, cotinine, anatabine, and anabasine) on food intake, one of the key regulators of body weight. In addition, a smokeless tobacco extract (STE) and e-cigarette (EC) refill liquid were used to model the effects of actual tobacco product exposure on food intake. Male Holztman rats were trained to lever press for food pellets during daily 2h sessions in operant chambers. In Experiment 1, the effects of subcutaneous injections of saline, nicotine (0.25–1.00mg/kg), nornicotine (0.50–6.00mg/kg), cotinine (1.00–100.00mg/kg), anatabine (0.25–3.00mg/kg), and anabasine (0.50–4.00mg/kg) were assessed. In Experiment 2, rats from Experiment 1 were used to examine the effects of nicotine, STE, and EC liquid. All alkaloids, except cotinine, produced a dose-dependent reduction in overall food intake. The highest doses of all drugs significantly reduced latency and response rate to obtain the first pellet. At some doses, nicotine, anatabine, and nornicotine reduced food intake within the first 45min without compensatory increases in intake later in the session. STE and EC liquid produced dose dependent decreases in food intake similar to nicotine alone. These data suggest that minor tobacco alkaloids have appetite suppressant effects and warrant further investigation into their effects on body weight, energy intake, and energy expenditure under free-feeding conditions. However, findings with STE and EC liquid suggest that nicotine is the primary constituent in these products to affect food intake, whereas levels of minor alkaloids in these products may be too low to influence food intake.

High-fat diet meal patterns during and after continuous nicotine treatment in male rats.

Smoking to control body weight is an obstacle to smoking cessation, particularly in western cultures where diets are often rich in calories derived from fat sources. The purpose of this study was to investigate the effects of continuous nicotine administration on meal patterns in rats fed a high-fat diet. Male rats were housed in cages designed to continuously monitor food intake and implanted with minipumps to deliver approximately 1.00 mg/kg/day of nicotine or saline. Meal patterns and body weights were assessed for 2 weeks of treatment and 1 week posttreatment. When compared with controls, rats with continuous nicotine treatment exhibited a decrease in the average meal duration(s) during the first week of treatment and a modest, yet sustained reduction in daily number of meals over the 14-day treatment period. Nicotine-induced decreases in body weight gain were observed throughout the 2 weeks of treatment. No differences in meal patterns or body weight gain were seen for 1 week following cessation of treatment. Results from this study suggest that while continuous nicotine treatment decreases daily food intake, meal durations, meal numbers, and weight gain, cessation of this treatment does not result in significant compensatory increases. Understanding the effects of nicotine on feeding patterns and weight gain may allow for improvements in treatment protocols aimed at addressing the factors that contribute to tobacco use. (PsycINFO Database Record

The effects of extended intravenous nicotine administration on body weight and meal patterns in male Sprague–Dawley Rats

Increased appetite and weight gain after cessation is a deterrent for quitting smoking. Attempts to understand the mechanism for these effects using animals have been hampered by the difficulty or inconsistency of modeling the effects seen in humans. To examine the effects of extended daily access to intravenous nicotine, via programmed infusions, on body weight and meal patterns in rats. Intravenous (IV) nicotine infusions (0.06 mg/kg/inf) were administered noncontingently, every 30 min throughout the dark cycle and the last 3 h of the light cycle, to emulate self-administration. The effect of these infusions on food intake, meal patterns, and weight change were examined relative to a control group during treatment and in a post-nicotine phase. Nicotine-treated rats gained half the weight that vehicle treated animals gained and ate approximately 20 % less food overall than vehicle-treated rats. Whereas a compensatory increase in meal frequency occurred during the dark period to account for smaller meals, no compensation was observed throughout the light period. In a post-nicotine phase, the nicotine group maintained a lower weight for 1 week and then gained weight back to control levels. The rate of weight gain post-cessation was faster in animals that had received nicotine compared to controls. Compared to previous studies examining the effects of minipump or intraperitoneal injections of nicotine on food intake, the present study was able to detect previously unknown circadian differences in meal patterns which will be important in the development of smoking cessation and weight gain prevention drugs.

Evidence for the role of hindbrain orexin-1 receptors in the control of meal size

Hypothalamic orexin neurons project to the hindbrain, and 4th-ventricle intracerebroventricular (4th-icv) injection of orexin-A treatment increases food intake. We assessed the effects of hindbrain orexin-A and the orexin-1-receptor antagonist SB334867 on meal pattern in rats consuming standard chow. When injected 4th-icv shortly before dark onset, lower doses of orexin-A increased food intake over a 2-h period by increasing the size of the first meal relative to vehicle, whereas the highest dose increased food intake by causing the second meal to be taken sooner. Conversely, hindbrain SB334867 reduced food intake by decreasing the size of the first meal of the dark phase. We also examined the effects of 4th-icv orexin-A and SB334867 on locomotor activity. Only the highest dose of orexin-A increased activity, and SB334867 had no effect. In addition, hindbrain SB334867 induced c-Fos in the nucleus of the solitary tract. These data support the suggestion that endogenous hindbrain orexin-A acts to limit satiation. Both orexin-A and the pancreatic satiation hormone amylin require an intact area postrema to affect food intake, so we asked whether 4th-icv orexin-A impairs the satiating effect of peripheral amylin treatment. Amylin reduced the size of the first meal of the dark cycle when rats were pretreated with 4th-icv saline, yet amylin was ineffective after 4th-icv orexin-A pretreatment. Using double-label immunohistochemistry, we determined that some orexin-A fibers in the area postrema are located in proximity to amylin-responsive neurons. Therefore, hindbrain orexin-A may increase food intake, in part, by reducing the ability of rats to respond to amylin during a meal.

Assessment of the cannabinoid-1 receptor antagonist AM251 as an unconditioned stimulus in taste aversion conditioning and its effects on meal patterns in rats

Assessment of the cannabinoid-1 receptor antagonist AM251 as an unconditioned stimulus in taste aversion conditioning and its effects on meal patterns in rats

The effect of branched-chain amino acids (BCAA) on meal pattern of rats

BCAA (isoleucine, leucine and valine) have been reported to enhance food intake and have been used as anti-anorectic agents, especially in critically-ill patients. However, it is not clear whether their stimulatory effect on food intake is the result of an increase in meal size and/or meal number. Furthermore, the impact of individual BCAA on food intake is not well documented. The present experiment was designed to investigate the effect of individual BCAA on meal patterns of rats. Twenty-four adult male Sprague-Dawley rats were randomly divided into four equal groups and fed control diet or diets supplemented with isoleucine, leucine or valine (50 g/kg). Feeding patterns were monitored for 2 weeks using feed recording equipment (model 80350 series; Campden Instruments Limited, Lafayette, IN, USA).

Systemic mazindol reduces food intake in rats via suppression of meal size and meal number

The aim of the present study was to determine the impact of the appetite suppressant mazindol on meal pattern in rats. Meal patterns were monitored in adult male rats after mazindol dosing during the first three hours of the dark cycle using automated feeding chambers (BioDAQ). Mazindol (0, 0.25, 1.25 and 2.5 mg/kg, IP) produced a dose-dependent hypophagia and hypodipsia. Meal size and meal number were significantly suppressed by mazindol. The meal pattern findings indicate that mazindol inhibits eating in the rat via a suppression of both meal size and meal number.

Adaptation of lipid-induced satiation is not dependent on caloric density in rats

Food intake is modulated by ingestive (gastrointestinal) and post-ingestive signals; ingested fat is potent to produce short-term satiety (satiation) but this can be modified by long-term ingestion of a high fat diet. Aim Determine whether altered lipid-induced satiation is dependent on the fat content of the diet, rather than increased caloric density or changes in adiposity. Methods Initial experiments determined the differences in the microstructure of meal patterns in rats fed a high fat diet (HF: 38% fat kcal) and in rats pair-fed an isocaloric, isonitrogenous low fat diet (LF: 10% fat kcal) and changes in meal patterns measured after long-term maintenance on the HF diet. Results Rats fed the HF diet had a significant 50% increase in meal frequency compared to rats fed the LF diet; in addition, there was a significant reduction in meal size (32%) and inter meal interval (38%) consistent with induction of satiation. After 8 weeks on the HF diet, these parameters tend to approach those of rats maintained on the LF diet. There was a significant 56% decrease in the activation of neurons in the NTS in response to intragastric gavage of lipid in rats maintained for 8 weeks on the HF compared to LF diet. Conclusion Dietary fat alters meal patterns consistent with induction of a short-term satiety signal. This signal is attenuated with long-term exposure to dietary lipid, in the absence of ingestion of additional calories or changes in body weight. This adaptation of short-term satiety might contribute to diet-induced obesity.

Comparison of the effects of chronic central administration and chronic peripheral administration of islet amyloid polypeptide on food intake and meal pattern in the rat

Islet amyloid polypeptide (IAPP) is postulated to act as a hormonal signal from the pancreas to the brain to inhibit food intake and reduce adipose energy reserves. The present study compared the effects of chronic peripheral and chronic central administration of IAPP on food intake and meal pattern in rats. IAPP was administered subcutaneously (SC) for 7 days at doses of 0, 0.25, 2.5 and 25 pmol kg −1 min −1 using an osmotic minipump or administered centrally at doses of 0, 0.025, 0.25 and 2.5 pmol kg −1 min −1 using an osmotic minipump connected to an intracerebroventricular (ICV) catheter inserted into the third ventricle. Both SC and ICV infusion decreased total food intake dose-dependently. The minimal effective dose was 2.5 pmol IAPP kg −1 min −1 for SC administration and 0.25 pmol kg −1 min −1 for ICV infusion. The decrease in food intake produced by infusion of IAPP was mainly due to decreased meal size, although a significant decrease in meal number also occurred at the highest SC and ICV doses. SC administration produced a larger, more persistent decrease in food intake during the light period than in the dark period, while ICV infusion caused a larger, more persistent decrease during the dark period. The 10-fold difference in minimal effective doses indicates that ICV-administered IAPP acted primarily in the brain to inhibit food intake. The difference between the effects of IAPP on meal pattern with the two methods of administration suggests that IAPP does not act on the same target(s) when administered centrally as it does when it is administered peripherally.

Meal patterns and body weight after nicotine in male rats as a function of chow or high-fat diet

Studies of the effects of nicotine (NIC) on meal patterns in rats often employ chow pellet diets that contain little fat, whereas humans using NIC commonly consume diets relatively rich in fat. The aim of the present study was therefore to compare the impact of NIC administration and NIC cessation on meal pattern in adult male rats offered a standard powdered chow (CHOW: 10.9% fat by calories) diet or a palatable high-fat (HIFAT: 58.3% fat by calories) diet. Computerized meal pattern analyses were conducted for male rats treated for 14 days with injections of either saline or 1.4 mg/kg/day of NIC (as the free base given in 5 equal amounts) during the dark phase and continued for 10 days after NIC cessation. The suppression of daily caloric intake by NIC was larger in HIFAT-NIC rats than in CHOW-NIC rats ( p < .01), such that NIC induced a greater suppression of body weight in HIFAT-NIC rats, relative to CHOW-NIC rats ( p < 0.02). NIC administration reduced MS in both CHOW and HIFAT rats. CHOW fed rats showed a gradual increase in meal number in response to NIC, whereas HIFAT fed rats showed a significant initial suppression of meal number, which returned to control levels by day 4 of the 14 day NIC treatment period. In addition, NIC increased water intake more in HIFAT fed rats than in CHOW rats. Cessation of NIC resulted in transient increases in daily caloric intake in CHOW and in HIFAT rats. The present study demonstrates that NIC actions on food intake suppression, meal patterns, and weight reduction differ depending on whether the rats are fed low- or high-fat diets.

Meal patterns in male rats during and after intermittent nicotine administration

Continuous administration of nicotine (NIC) reduces food intake (FI) and body weight (BW), whereas rebound eating and BW gain occur after NIC cessation. However, generalizations derived from prior studies on meal patterns in rats using continuous 24-h NIC administration are limited, because human smokers use NIC intermittently during their active period. In the present study, computerized meal pattern analyses (MPA) were conducted for adult male rats treated for 14 days with either saline or 2 or 4 mg/kg/day of NIC spread over five equal amounts during the dark phase. MPA analyses continued for 14 days after cessation of NIC. Only the 4 mg/kg/day NIC dose caused consistent changes in meal patterns and only that dose is reported herein. Dark period FI was reduced, whereas light period FI was unchanged in the NIC-treated group; thus, there was no rebound eating during the 12-h nontreatment phase. MPA analyses revealed the FI reduction on Day 1 of NIC administration was caused by a persistent decrease in dark phase meal size. On Day 5 of NIC, the rats compensated by significantly increasing the number of meals they took, which tended to normalize dark phase FI. Congruently, dark phase intermeal interval was decreased. Importantly, these changes in meal patterns persisted for 2 weeks after termination of NIC. Upon NIC cessation, the NIC group had a transient elevated FI. The NIC-treated group's BW was significantly suppressed by Day 6 of NIC and after stoppage these rats slowly, but incompletely, regained lost BW over the next 14 days. These results document that administration of NIC during the dark phase resulted in a reorganization of the microstructure of FI in male rats and that long-lasting alterations in the microstructure of FI (e.g., meal size and meal number) were noted for up to 2 weeks after cessation of NIC. These results differ from studies in which NIC was given continuously 24-h/day and indicate that dark phase NIC administration in rats may represent an appropriate model to study the impact of NIC on meal patterns.

Chronic infusion of islet amyloid polypeptide causes anorexia in rats.

Islet amyloid polypeptide (IAPP) is a hormonal peptide that at high doses has been shown to reduce food intake. In the present study, the dose-response effects of subcutaneous infusion of IAPP (0, 2, 7, and 25 pmol.kg-1.min-1) for 8 days on food intake and meal patterns in rats were investigated. At the end of the experiment, plasma was obtained and levels of IAPP were measured by radioimmunoassay. IAPP dose-dependently and transiently inhibited food intake. The minimal effective dose (2 pmol.kg-1.min-1) caused a small but significant (up to 14%, P < 0.01) inhibition of food intake that lasted 5 days. The highest dose administered (25 pmol.kg-1.min-1) had the greatest effect (up to 44%, P < 0.001), which lasted throughout the 8-day period. Reductions in feeding during light and dark phases occurred through a decrease in number of meals consumed rather than meal size or meal duration. IAPP also decreased body weight gain and water intake dose dependently. IAPP infusion of 2, 7, and 25 pmol.kg-1.min-1 increased plasma IAPP concentrations from a basal level of 10.3 +/- 0.7 pM to 35.1 +/- 5.4, 78.1 +/- 11.2, and 236.6 +/- 23.6 pM, respectively, values that are likely to be close to physiological and within the pathophysiological ranges. Thus IAPP may play an important physiological or pathophysiological role in control of food intake.

Meal Patterns Reveal Differential Effects of Vagotomy and Tropisetron on Responses to Indispensable Amino Acid Deficiency in Rats

Rats offered an amino acid-imbalanced diet (IMB) respond to the ensuing amino acid deficiency rapidly with a decrease in food intake of at least 50%. Pretreatment with tropisetron (TROP), an antagonist at serotonin3 (5-HT3) and 5-HT4 receptors, increases intake of IMB to approximately 85% of control. Vagotomy has two effects: it increases intake of an IMB to about 65%, and also blocks the increased response to tropisetron. This indicates that the greater IMB intake after tropisetron, ∼20% more than in vagotomized rats, is dependent on an intact vagus. Rats were either 1) vagotomized or sham-operated, or 2) given tropisetron or saline injections. We then examined free-feeding meal patterns in rats fed an IMB to determine whether the microstructure of the feeding behavior differed, either between treatments, or by comparison with the meal patterns in rats fed the control diet. Vagotomy did not alter meal patterns in rats consuming the basal control diet. During the first 6 h after introduction of the IMB, the control rats showed significantly longer intermeal intervals (over twice the length of intervals recorded in those fed the basal diet), with corresponding effects on meal numbers, which were restored to basal values in tropisetron and vagotomized rats. Meal size was increased after vagotomy also. After 6 h, in intact tropisetron-treated rats only, a fourfold faster rate of eating throughout the late dark period accounted for the significantly greater intake of the IMB than in controls. The results demonstrated differential effects of the two treatments on the anorectic responses to amino acid deficiency.

Effects of duodenal and distal ileal infusions of glucose and oleic acid on meal patterns in rats.

The mechanisms mediating the anorexic effects of nutrients in the proximal and distal small intestine are not clearly understood. We determined the dose-dependent effects of duodenal and distal ileal infusions of glucose and oleic acid on meal patterns in ad libitum feeding rats. Rats with cannulas in both the duodenum and ileum received a 2-h infusion of glucose (0, 800, 1,600, 3,200, 6,400, or 12,800 mumol/h) or oleic acid (0, 48, 240, 640, or 1,280 mumol/h) into the duodenum or ileum at the start of the dark period, and meal patterns were monitored for 4 h. Cumulative food intake was inhibited dose dependently by ileal as well as duodenal infusion of both glucose and oleic acid. Ileal glucose was more inhibitory than duodenal glucose, whereas duodenal oleic acid was more inhibitory than ileal oleic acid. Duodenal glucose and oleic acid inhibited feeding by decreasing meal frequency; ileal oleic acid decreased only meal size, whereas ileal glucose reduced both meal size and frequency. We interpret these results to suggest that ileal oleic acid and glucose suppress feeding by different mechanisms and that these mechanisms differ from those mediating the anorexic responses to oleic acid and glucose in the duodenum.

Consistency of meal patterns in laboratory rats

Meal pattern measures (e.g., bout length and bout number) provide a detailed description of the elements of ingestion, and as a result they are theoretically more sensitive to experimental manipulation than simple measurements of total consumption over a fixed time period. For this reason, meal pattern measure are often used as a way to infer how rodents respond to tastants or how pharmacological or surgical treatments modify ingestive behavior. This approach relies on the assumption that under normal conditions, the meal patterns of individual rats are consistent across consecutive light-dark (L-D) cycles. If these patterns are inconsistent, then experimental designs involving meal patterns would have limited power, and thus require relatively large sample sizes. The present study critically evaluates the consistency assumption in Sprague-Dawley and Fisher-344 rats by monitoring meal patterns over 10 consecutive L-D cycles. For each rat, the following feeding and drinking measures were determined: total daily intake, duration of night bouts, number of night bouts, and number of licks per night bout. The analysis excluded daytime ingestive measures owing to their infrequent occurrence. Ingestive measures were highly consistent across time in all Sprague-Dawleys, but in only a minority of the Fisher-344s. The distribution of feeding and drinking activity throughout each night was also determined in the same rats. Whereas Sprague-Dawleys displayed lights-off and lights-on peaks of ingestive activity, only a minority of Fisher-344s displayed a consistent lights-on peak of ingestive activity. It is concluded that rat strains can differ with respect to the consistency of meal patterning, and that such strain differences should be considered in future comparative studies of meal patterns in rats.

Diurnal variation in the effects of type A CCK receptor antagonist devazepide on meal patterns in rats.

Diurnal variation in the effects of type A CCK receptor antagonist devazepide on meal patterns in rats.

The effect of patch depletion on meal patterns in rats

Abstract. Animals exploiting patchily-distributed resources must decide when to leave a given patch and seek another. If economically based, this decision will depend on the rate of return in the patch, the cost of moving to a new patch, and the overall rate of return in the environment. This study examined how these economic considerations may influence the pattern of daily food intake, i.e. the meal pattern. Laboratory rats lived continuously in a simulated depleting-patch environment in which the cost of beginning a meal in a new patch was controlled by a fixed-ratio price of access to the feeder and the rate of patch depletion was controlled with progressive-ratio schedules of pellet cost. As predicted by a cost-minimizing model, patch leaving was a joint function of the size of the progressive ratio and the size of the access cost: meals were smaller at higher depletion rates, but larger at higher access costs. However, meals were somewhat larger than the size that would have minimized feeding time and reliably larger than the size that would have minimized response output. Furthermore, although meal frequency changed in the opposite directions from meal size, the changes were not entirely compensatory; daily intake and body weight declined in the higher-cost conditions. These results suggest that intake patterns are the result of compromises between economic and physiological requirements.