Differences between alcohol-preferring and alcohol-nonpreferring rats in ethanol generalization.

Alcohol-preferring (P rats) and alcohol-nonpreferring rats (NP rats) were trained to discriminate intraperitoneal injections of 0.5 g/kg ethanol, or subcutaneous injections of 0.6 mg/kg nicotine from saline. P rats learned the ethanol discrimination more rapidly and made a higher percentage (88%) of their responses on the ethanol lever after ethanol and a lower percentage (7%) after saline than NP rats (78 and 15%, respectively). In substitution tests, increasing doses of ethanol produced increases in the percentage of responses on the ethanol lever with similar ED50s (0.43 and 0.44 g/kg) in P and NP rats. P rats trained to discriminate ethanol from saline made more responses on the ethanol lever after nicotine (80%) and d-amphetamine (63%) than NP rats (33 and 40%). The ethanol stimulus did not generalize to morphine in either P or NP rats. NP rats trained to discriminate ethanol from saline responded more on the ethanol lever after bupropion (77%) than P rats (49%). In rats trained to discriminate nicotine from saline, the nicotine discriminative stimulus did not generalize to ethanol in either P or NP rats, suggesting that the genetic difference in the stimulus generalization of ethanol was not symmetrical.

Effect of fat-free potato chips with and without nutrition labels on fat and energy intakes.

This study investigated the effect on fat and energy intakes of fat-free potato chips made with olestra compared with regular potato chips. Ninety-five participants (unrestrained and restrained males and females) were tested in 2 conditions. In the information condition, participants were given nutrition information about the chips and were aware that the chips differed in fat and energy contents. In the no-information condition, participants were not aware of the differences. In both conditions, participants ate either regular or fat-free potato chips ad libitum for an afternoon snack in a crossover design in two 10-d periods. To assess 24-h intake, participants completed food diaries twice in each 10-d period. The results showed that all groups significantly reduced their fat and energy intakes in the snack when eating the fat-free chips compared with the regular chips (P< 0.0001). Also, potato chip intake did not differ across time for either type of chip. Over 24 h all participants had lower fat intakes (P< 0.05) when eating the fat-free potato chips compared with the regular chips, but 24-h energy intake was not significantly different between groups. When information was provided, restrained participants ate more of the fat-free chips than the regular chips; however, this increase did not negate the reductions in fat and energy associated with eating the fat-free chips. This study showed that substituting fat-free (olestra-containing) potato chips for regular-fat chips can help reduce fat and energy intakes in short-term (within meal) situations and reduce fat intake over 24 h.

Videotape assessment of changes in aberrant meal-time behaviors in anorexia nervosa after treatment.

This study compared meal-time behaviors in patients with anorexia nervosa to normal-weight controls and the effects of hospital treatment on these behaviors. Ten restricting-anorexics and six normal-weight controls were given a standard lunch and asked to eat the entire meal. Their behaviors were recorded via hidden camera. All participants were tested twice--anorexics before and after in-patient treatment, and controls at similar intervals. Videotapes of these sessions were analysed for occurrence and duration of eight categories of non-ingestive behaviors: food manipulation, food preparation, food moving, non-food manipulation, concealment, vigilance, passivity and physical activity. Food-ingestion patterns, including number of bites of food and switches between different kinds of food, were also recorded. Results indicated that anorexics spent significantly more time than controls in behaviors that were directly food-related, and exhibited more vigilance behavior. Pre-treatment anorexics spent significantly more time in these behaviors than did post-treatment anorexics. Few group differences or treatment effects were found in food-ingestion patterns, although there was an indication that both pre- and post-treatment anorexics avoided high-fat foods more than controls did. These results suggest that videotaping provides a useful technique for characterizing the behavior associated with eating disorders. Further studies should explore whether normalization of these behaviors is associated with a positive clinical outcome.

Sibutramine reduces food intake in non-dieting women with obesity.

Sibutramine (SIB), an inhibitor of serotonin and noradrenaline reuptake, has been shown in clinical trials to be associated with a dose-related decrease in bodyweight. This double-blind, placebo-controlled, Latin square crossover study examined whether the effect on bodyweight could be due in part to a reduction in daily food intake. Twelve non-dieting, women with obesity (body mass index of 30.5 to 41.9) received three treatments (0 [matching placebo], 10, or 30 mg SIB/day) for 14 days, with 14-day washout periods in between. On days 7 and 14, participants came to the laboratory to eat breakfast, lunch, and dinner so that daily energy and macronutrient intakes and ratings of hunger and satiety could be measured. Significant reductions occurred in food intake (both grams and energy) over the 14-day study period. On day 7, SIB 30 reduced intake significantly by 1762 kJ (23% reduction from placebo), and on day 14, both SIB 10 and SIB 30 significantly reduced intake compared with placebo (SIB 10, 19% reduction [1490 kJ]; SIB 30, 26% reduction [2079 kJ]). On day 7, the percentage of energy consumed from carbohydrate increased significantly with the 30-mg dose (56.7%) compared with that of placebo (51.4%), with a reciprocal decrease in energy from fat (27.8% to 24%). The results show that SIB reduced energy intake in women with obesity who were not attempting to lose weight.

Sensory properties of a nonabsorbable fat substitute did not affect regulation of energy intake.

Many reduced-fat foods retain the sensory properties of their high-fat counterparts through the use of fat substitutes. This study examined whether regulation of energy intake is affected when the nonabsorbable fat substitute olestra is used to uncouple the sensory properties of fat from fat absorption and metabolism. Cream of broccoli soups were developed in three versions: fat-free, fat-free+olestra (33.3 g olestra), and high-fat (33.3 g fat) (923900 and 2150 kJ per serving, respectively). The olestra soup had the nutrient composition of the fat-free soup but the sensory properties of the high-fat soup. Subjects were grouped by sex, body weight, and dietary restraint (total n = 67). Subjects had either no preload (control) or a soup preload (465 g) followed by a self-selection lunch. Intake was measured at lunch, dinner, snack, and breakfast. At lunch, the response to the soup preloads was not affected by sex, dietary restraint, or body weight. Energy intake (soup+lunch) was significantly greater in the high-fat than in the control condition (P < 0.05), but energy intake in the fat-free and olestra-soup conditions was not significantly different from that in the control condition (3570, 3352, 3464, and 4457 kJ in control, fat-free, olestra, and high-fat soup conditions, respectively). Thus, subjects compensated completely for the energy in the fat-free and olestra soups but not for the energy in the high-fat soup. No differences were found in the response to the two fat-free conditions, one with the fatty taste and one without. In this study the sensory properties of fat alone, ie, apart from the physiologic effects of fat, did not affect energy regulation.

Changes in food intake in response to stress in men and women: psychological factors.

The relationship between psychological factors and changes in food intake during stress (both during a specific experience and during stress, in general) in 49 men, ages 18 to 34, and 52 women, ages 18 to 35, was assessed using questionnaires. Participants completed the State-Trait Anxiety Inventory, the Eating Inventory (which includes scales for disinhibition, cognitive restraint and perceived hunger) the Restraint Scale, the Eating Attitudes Test and the Binge Scale; and reported their height and weight. Men and women were divided into two groups regarding changes in eating habits during stress: increased intake and no increased intake. There were no significant differences between genders in the proportions of participants in each group. However, correlational analyses revealed different patterns of associations for males and females. For females, high scores on disinhibition were significantly correlated with eating more than usual during a specific stressful experience (r = 0.51, p < 0.001) as well as during stress, in general (r = 0.66, p < 0.001), while high scores on cognitive restraint were not. For males, neither disinhibition nor cognitive restraint were associated with the relationship between eating and stress. Scores on disinhibition discriminated over 80% of females who reported increased intake during stress from those who reported no increased intake. In females, the inability to maintain control of self-imposed rules concerning food intake is an important factor in the relationship between stress and eating.

Age-related impairments in the regulation of food intake.

Low food intake in elderly individuals increases the risk for many nutrition-related acute or chronic illnesses. It is not known whether aging is associated with changes in hunger and satiety, or whether elderly individuals can regulate energy intake in response to manipulations of the energy or nutrient content of foods. Therefore, this study investigated short-term energy regulation in healthy elderly (n = 16; aged 60-84 y) and young (n = 16; aged 18-35 y) men. Participants were given yogurt preloads that varied in energy and macronutrient content (low-fat, low-energy, 962 kJ; high-fat, high-energy, 2134 kJ; high-carbohydrate, high-energy 2134 kJ), or no yogurt, followed by a self-selected lunch (presented 30 min after subjects began to consume the yogurt). Energy intake, the percentage of macronutrients consumed in the meals, and subjective sensations of hunger and satiety were analyzed. The elderly men consumed significantly less energy than the young men in the baseline (no yogurt) condition. Lower intake was concordant with subjective sensations of satiety; visual analog data indicated that the older men were less hungry and more full at the start of lunch. Compensation for energy in the preloads was less precise in the elderly than in the young men, in that elderly men consistently overate at the self-selected lunch. Young men consumed +/- 10% total energy (lunch + yogurt) in the yogurt preload conditions compared with their baseline intake; elderly men overate between 10% and 30% in relation to their baseline intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Information about the fat content of preloads influences energy intake in healthy women.

OBJECTIVE: This study tested the hypothesis that the perceived fat content of a preload (a required first course) influences subsequent food and energy intake. SUBJECTS AND DESIGN: Forty-eight healthy, nondieting women (24 restrained, 24 unrestrained) were given a fixed amount (350 g) of three different yogurts (low-fat, low-calorie; low-fat, high-calorie; high-fat, high-calorie), or no yogurt, followed by lunch (30 minutes after the yogurt preload was served) and dinner (4.5 hours later). Each subject was tested in all four conditions in a counterbalanced design. Half of the subjects received accurate information, in the form of a label, about the fat content of the yogurts, which did not necessarily correspond to energy content; the other half received no information. ANALYSES: Energy intake, the percentage of macronutrients in the meals, and subjective sensations of hunger and satiety were analyzed. RESULTS: No effect of restraint was noted in the intake analyses. A significant information-by-preload interaction (P < .05) was found. Subjects who had information consumed more energy at lunch after eating a preload labeled low fat than after eating a preload with similar energy content but labeled high fat. The opposite response was seen in women who did not receive information. When energy consumed at dinner was included in the analyses, overall intake was still significantly greater in the women who received information and ate a low-fat preload. No differences were found in the percentage of macronutrients selected or in subjective sensations after consumption of any of the preloads. CONCLUSIONS: Messages about the fat content of a food can influence energy intake in healthy women.

Accurate energy compensation for intragastric and oral nutrients in lean males.

Lean healthy males received either parenteral or enteral infusions of pure fat or carbohydrate (2092 kJ), or isotonic saline, to determine their influences on food intake and energy regulation in self-selected lunch and dinner meals. In the first study, six males received intravenous infusions for 3.5 h in the morning, followed by lunch 30 min after the infusion ended and dinner 6 h later. No compensation was seen for energy differences in intravenous infusions. In the second study, six males received intragastric infusions for 15 min or 3.5 h. Rapid intragastric infusions of fat or carbohydrate and slow infusions of fat significantly reduced intake at lunch, whereas slow carbohydrate infusions did not. In both studies, subjects reduced intake at lunch 30 min after 2092-kJ yogurt preloads varying in fat and carbohydrate, demonstrating their ability to respond to orally derived energy. These results support the existence of mechanisms in the gastrointestinal tract for the rapid detection of the energy content of ingested nutrients or foods in lean males.

Mother as shield: differential effects of contact and nursing on pain responsivity in infant rats--evidence for nonopioid mediation.

To determine how rat mothers protect their pups against pain, we applied focal heat (34-51 degrees C) to the ear or shoulder of 10-day-old rats that were isolated, in contact among themselves or with their mother, suckling nonnutritively, or in the hyperextension position normally caused by milk letdown. Relative to isolated rats, contact doubled withdrawal latencies from heat (43 or 45 degrees C) applied to the ear. Suckling quadrupled heat-escape latencies. During hyperextension, rats essentially did not escape from thermal stimulation of up to 48 degrees C. Protection provided by maternal contact, especially suckling, was not mediated by either mu or kappa opioid receptors: neither systemic injections of naltrexone nor norbinaltorphimine reduced heat-escape latencies. Morphine (0.125 and 0.250 mg/kg) added to the effects of contact but multiplied the effects of suckling to produce heat-escape latencies that were upward of 2 min.

Some comparisons among the calming and pain-relieving effects of sucrose, glucose, fructose and lactose in infant rats.

Ultrasonic vocalizations were recorded from 10-day-old albino rats while they were isolated from their dam and siblings. Each rat received a 1.0% BW intra-oral infusion of sucrose, fructose, glucose or lactose at a concentration range of 0.22-0.66 M for 3 min and their vocalizations were determined during the infusion and for an additional 7 min. Sucrose, fructose and glucose all significantly reduced vocalizations to about 50% of baseline levels, whereas lactose, the milk sugar, was ineffective. Moreover, the dose-response function was flat for the three effective sugars. In a second experiment, the effects of these sugars on heat escape latency were measured. Sucrose, fructose and glucose each elevated the latency with which infant rats removed a paw from a 48 degrees C surface; lactose did not. These findings of lactose ineffectiveness and the flat dose-response function for the other three sugars exactly parallel those obtained for human newborns. Their implications are discussed.

Endogenous cholecystokinin reduces vocalization in isolated 10-day-old rats.

Devazepide, the cholecystokinin (CCK) A receptor blocker, markedly and specifically affected the behavior of 10-day-old rats isolated from their mother and siblings. Whereas intraoral infusions of milk or fat, which cause CCK release, calmed infants, that is, reduced levels of ultrasonic vocalization, devazepide fully blocked this reduction. Devazepide did not affect calming caused by sucrose infusions, which do not release CCK. Moreover, devazepide did not reduce the elevated pain limen caused by milk or fat infusions. These data parallel earlier findings obtained with administration of exogenous CCK and implicate endogenous CCK in the maintenance of infant steady state and calm. The possibility that CCK contributes to the normal development of mother-infant affectional systems is discussed.

The influence of dietary fat on food intake and body weight.

Excessive intake of dietary fat is associated with a number of nutrition-related disorders, including obesity, heart disease, and cancer. The over-consumption of fat may be related to its palatability, high energy density, or physiological effects. This article reviews possible reasons why fat intake is high, examines the relationship between diet composition and body weight, and explores potential fat reduction strategies. It is concluded that low-fat or fat-free products could be useful in reducing the percentage of calories derived from fat, although this assertion needs to be further tested in controlled laboratory experiments and validated on a population basis.

Opioid mediation of odor preferences induced by sugar and fat in 6-day-old rats.

Intraoral infusions of sucrose, fat or polycose reduce ultrasonic vocalizations during isolation, and increase pain threshold in infant rats. These effects are naltrexone reversible. The present study determined whether these substances, when paired with an odor, caused a change in preference for that odor. In 6-day-old rats, pairing orange odor with intraoral infusions of sucrose or corn oil, but not polycose, water, mineral oil or 0.01% quinine hydrochloride, caused a substantial increase in preference for orange. Preference formation was blocked by systemic injection of naltrexone (0.25 mg/kg) prior to pairing orange with either sucrose or corn oil. Moreover, preference expression was prevented by naltrexone injection prior to testing. Thus certain substances thought to reduce stress in infant rats via endogenous opioid release can also cause preference for substances that predict their occurrence. Preference formation depends upon the availability of endogenous opioids. Preference expression reflects the conditioned stimulus causing opioid release.

Opioidlike effects of intraoral infusions of corn oil and polycose on stress reactions in 10-day-old rats.

The effects of intraoral infusions of corn oil and the polysaccharide Polycose on behavioral reactions to pain and to social isolation were studied in 10-day-old albino rat pups. Both substances significantly increased paw-lift latencies (a measure of pain response) and reduced the number of ultrasonic vocalizations (a measure of isolation distress). Moreover, elevated pain thresholds were normalized by naltrexone (0.25 mg/kg) pretreatment, and the quieting of vocalizations was abolished by pretreatment. These findings indicate an interaction between ingestion, pain, and distress systems in neonatal rats and suggest that fats and polysaccharides influence these systems via endogenous opioids.

Stress-reducing effects of ingesting milk, sugars, and fats. A developmental perspective.

A developmental approach to the study of feeding is proposed that considers social complexity and its biological mediation as core determinants of later ingestive patterns. Evidence is presented for opioid-mediated influences of milk and its major constituents and for nonopioid-mediated channels for contact comfort. Consideration of these factors might help us better understand some of the determinants of human feeding disorders such as bulimia and anorexia nervosa.