Do Obese Eat Faster Than Lean Subjects? Food Intake Studies in Pima Indian Men

Food intake rate has previously been derived from observation of eating behavior in laboratory settings or in public eating establishments. Although it has been suggested that obese individuals eat faster than lean individuals, observations of such an “obese eating style” have yielded mixed results. In the present study, the relationship between ad-libitum food intake rate and obesity was evaluated over 4 days on a metabolic ward in 28 healthy Pima Indian men (Mean ± SD; 29 ± 7 y, 100.4 ± 27.1 kg, 33 ± 10% body fat) using an automated food selection system containing a large variety of foods . Total energy intake averaged 18829 ± 3299 kJ/d consisting of 47 ± 4,40 ± 3, and 13 ± 1 percent of carbohydrate, fat and protein, respectively. The average meal duration was 25 ± 7 min. Food intake rate was 68 ± 21 g/min while carbohydrate, fat and protein intake rates were 23 ± 6, 9 ± 3 and 6 ± 2 g/min, respectively. Food intake rate correlated negatively with %body fat (1=0.61, P<0.01). Similar relationships were found between the intake rates of carbohydrate, fat and protein and body fatness. Only prospective studies will indicate whether a slow food intake rate may contribute to the etiology of obesity by possibly reducing satiety .     

Intermittent nicotine administration modulates food intake in rats by acting on nicotine receptors localized to the brainstem

Previous studies have shown nicotine (NIC) administration leads to decreased food intake, while other investigations have reported that NIC stimulates c-Fos expression in the brainstem. Whether there is a causal relationship between NIC effects on ingestion and its effect on brainstem neurons is uncertain, however we hypothesized that blocking NIC action in the brainstem would prevent, to some extent, the hypophagic effects of NIC. In the present study, cannulas were placed in the fourth ventricle of rats. A dose of NIC or saline was injected i.p. in four equal injections during the dark phase for four days. At the start of the second day of injections the NIC receptor antagonist mecamylamine (MEC) or artificial cerebrospinal fluid (a-CSF) was infused intracerebroventricularly (i.c.v.). Thus, four experimental groups were examined: a-CSF + SAL; a-CSF + NIC; MEC + SAL; MEC + NIC. Meal patterns were recorded using a computerized system and water intake and body weight were measured daily. Peripheral NIC injections suppressed food intake by decreasing meal size, whereas infusion of the NIC receptor antagonist MEC (4 microg) into the fourth ventricle blocked the NIC suppression of food intake. Moreover, the MEC effect was due primarily to an increase in dark phase meal size, which suggests neurons localized to the brainstem transmit NIC signals that regulate feeding behavior by affecting meal size.     

Amylin receptor blockade stimulates food intake in rats

Amylin is postulated to act as a hormonal signal from the pancreas to the brain to inhibit food intake and regulate energy reserves. Amylin potently reduces food intake, body weight, and adiposity when administered systemically or into the brain. Whether selective blockade of endogenous amylin action increases food intake and adiposity remains to be clearly established. In the present study, the amylin receptor antagonist acetyl-[Asn(30), Tyr(32)] sCT-(8-32) (AC187) was used to assess whether action of endogenous amylin is essential for normal satiation to occur. Non-food-deprived rats received a 3- to 4-h intravenous infusion of AC187 (60-2,000 pmol.kg(-1).min(-1)), either alone or coadministered with a 3-h intravenous infusion of amylin (2.5 or 5 pmol.kg(-1).min(-1)) or a 2-h intragastric infusion of an elemental liquid diet (4 kcal/h). Infusions began just before dark onset. Food intake and meal patterns during the first 4 h of the dark period were determined from continuous computer recordings of changes in food bowl weight. Amylin inhibited food intake by approximately 50%, and AC187 attenuated this response by approximately 50%. AC187 dose-dependently stimulated food intake (maximal increases from 76 to 171%), whether administered alone or with an intragastric infusion of liquid diet. Amylin reduced mean meal size and meal frequency, AC187 attenuated these responses, and AC187 administration alone increased mean meal size and meal frequency. These results support the hypothesis that endogenous amylin plays an essential role in reducing meal size and increasing the postmeal interval of satiety.     

Ghrelin response to protein and carbohydrate meals in relation to food intake and glycerol levels in obese subjects

Obese subjects have lower basal and an attenuated decrease of postprandial plasma ghrelin following carbohydrate-rich meals, while the response to protein is unknown. Therefore, plasma ghrelin levels were examined after ingestion of satiating amounts of a protein- or carbohydrate-rich meal in relation to food and energy intake and hunger/satiety ratings in 30 obese subjects followed 240 min later by ad lib sandwiches. Food intake and hunger/satiety ratings were identical while energy intake was significantly greater after bread (861 +/- 62.7 vs. 441 +/- 50.4 kcal, p < 0.001). Second meal food and energy intake were not different. Ghrelin decreased after bread, but increased by 50 pg/ml (p < 0.001) after meat. The corresponding increase of insulin was 55 vs. 9 microU/ml (p < 0.001). Glycerol levels decreased significantly less after the protein meal compared to carbohydrates. After protein glycerol was significantly correlated to the rise of ghrelin but not insulin. These data demonstrate that, in obese subjects, protein has no different satiating effect than carbohydrate despite divergent ghrelin levels. Energy intake corresponds to energy density of the respective food items. Ghrelin response to both meals is qualitatively similar but quantitatively attenuated compared to normal weight subjects. The relationship between ghrelin and glycerol would support recent observations of a possible role of ghrelin in fat metabolism.     

双低菜粕高水平替代饲料鱼粉对大黄鱼潜在风险的评估:生长、健康和营养价值

研究从生长、健康和营养价值方面评估了高水平的双低菜粕替代饲料鱼粉对大黄鱼潜在的危害。在鱼粉含量60%的基础饲料（FM）上按照质量分数用双低菜粕分别替代15%（CM15）、30%（CM30）、60%（CM60）和100%（CM100）的鱼粉,配制成5种实验饲料。每种饲料投喂5个网箱的大黄鱼[初重（135.38±1.02）g],即每个处理5个重复,进行12周的养殖实验。结果表明,当双低菜粕替代水平在15%和30%时,大黄鱼的生长及饲料系数并没有受到显著性的影响。然而,当替代水平高于30%时,大黄鱼的末重和特定生长率均显著降低,而饲料系数显著升高（P < 0.05）。当替代水平达到100%时,大黄鱼摄食率达到最高值而肥满度达到最低值（P < 0.05）。在组织形态方面,大黄鱼摄食双低菜粕替代的饲料后肠道绒毛的弯曲程度减少并且排列更加不规则,而肝细胞则呈现出圆形空泡状并伴随着细胞核的偏移。对大黄鱼骨骼进行X-射线扫描发现,摄食双低菜粕的大黄鱼椎体和头部出现了畸形。在营养价值方面,双低菜粕替代鱼粉并未显著影响大黄鱼背肌的脂肪含量、蛋白含量和氨基酸组成,然而脂肪酸组成受到了显著影响,即N-6系列脂肪酸含量显著升高,而DHA与EPA含量显著降低（P < 0.05）。根据欧洲食品安全局（EFSA）的相关标准,这些营养价值的变化并没有影响大黄鱼作为健康食品的功能。由此可见,高水平（60%和100%）的双低菜粕替代鱼粉对大黄鱼的负面影响主要表现为降低大黄鱼的生长性能、改变肠道和肝脏组织形态,以及影响大黄鱼的骨骼健康。然而,双低菜粕替代鱼粉养殖大黄鱼的肌肉仍然符合人类的膳食要求。因此,双低菜粕替代鱼粉并没有影响大黄鱼作为食用鱼的营养价值。     

The effects of ration level on food retention time in juvenile lemon sharks,Negaprion brevirostris

Synopsis Fecal production was monitored to observe the effects of meal size on retention time of food in the digestive tracts of lemon sharks, Negaprion brevirostris. Initial appearance of feces occurred more rapidly when ration level was increased. The onset of fecal production was negatively correlated with rate of intake. Production of feces continued for a longer period of time when meal size was increased. Retention time of food was directly related to feeding rate, suggesting that the rate of digestion was constant. The correlation between retention time and intake on a percentage body weight basis was greater than the correlation between retention time and intake on an energy density basis. The use of agar to bind food may have delayed digestion and prolonged food passage for sharks fed an experimental diet.     

Relationships between dietary sodium chloride, food intake and food conversion in the rainbow trout

The addition of up to 8.5 % sodium chloride to the diet of rainbow trout Salmo gairdneri had no significant effect on either food intake or food conversion efficiency. Over a range of rations from 4 % to 38 % of dry weight per week, there was a rectilinear relationship between ration and growth rate. The weight maintenance requirement and rate of weight loss during fasting were estimated from this relationship. Food conversion efficiency ( K ) increased from 0.00 at 4% dry weight per week food intake ( x ) to 0.19 at 38%, according to the equation K =0.21-0.77/x.     

The effect of feeding hierarchy on individual variability in daily feeding of rainbow trout, Oncorhynchus mykiss (Walbaum)

Three groups of rainbow trout, Oncorhynchus mykiss , (initial weight 40 g) were fed one of three rations (low, medium or high) for 73 days. Consumption by individual fish within the three ration groups was measured on four occasions (days 27, 55, 64 and 72) using radiography. Food intake by individual fish varied between days and this variability was expressed using the coefficient of variation (CV). Dominant fish within each ration group were defined as individuals with the greater share of the group meal and these fish had low CVs for food intake indicating relatively little variation in daily consumption. By contrast, the fish which had consumed a low mean proportion of the group meal displayed high CVs for food intake, indicating considerable variability in the sizes of individual meals consumed by these fish. As group ration increased, the range of meal sizes and individual CVs in daily feeding decreased, suggesting that the strength of the feeding hierarchy and the variability in individual consumption decreased as food availability increased. It is suggested that radiography can be used to assess social relationships within groups of fish allowing the assessment of feeding hierarchies in larger groups of fish than would be possible by observational techniques.     

Increased short-term food satiation and sensitivity to cholecystokinin in neurotrophin-4 knock-in mice

Neurotrophin-4 (NT-4) knockout mice exhibited decreased innervation of the small intestine by vagal intraganglionic laminar endings (IGLEs) and reduced food satiation. Recent findings suggested this innervation was increased in NT-4 knock-in (NT-4KI) mice. Therefore, to further investigate the relationship between intestinal IGLEs and satiation, meal patterns were characterized using solid and liquid diets, and cholecystokinin (CCK) effects on 30-min solid diet intake were examined in NT-4KI and wild-type mice. NT-4KI mice consuming the solid diet exhibited reduced meal size, suggesting increased satiation. However, compensation occurred through increased meal frequency, maintaining daily food intake and body weight gain similar to controls. Mutants fed the liquid diet displayed a decrease in intake rate, again implying increased satiation, but meal duration increased, which led to an increase in meal size. This was compensated for by decreased meal frequency, resulting in similar daily food intake and weight gain as controls. Importantly, these alterations in NT-4KI mice were opposite, or different, from those of NT-4 knockout mice, further supporting the hypothesis that they are specific to vagal afferent signaling. CCK suppressed short-term intake in mutants and controls, but the mutants exhibited larger suppressions at lower doses, implying they were more sensitive to CCK. Moreover, devazepide prevented this suppression, indicating this increased sensitivity was mediated by CCK-1 receptors. These results suggest that the NT-4 gene knock-in, probably involving increased intestinal IGLE innervation, altered short-term feeding, in particular by enhancing satiation and sensitivity to CCK, whereas long-term control of daily intake and body weight was unaffected.     

The effects of vitamin B6 deprivation with 4-deoxypyridoxine in meal-fed rats

Weanling male rats were trained to consume a control diet in one 4-hr meal a day. Rats were then fed one of three experimental diets for 7 days: (a) control diet minus B6 (-B6); (b) control diet (B6); or (c) control diet restricted to food intake of -B6 (B6R). Xanthurenic acid excretion was greater before and after a tryptophan load in -B6 than in B6R. Body weight gain, food intake, and food efficiency were not different between -B6 and B6. However, in B6R body weight gain, food intake and food efficiency were lower than that in both -B6 and B6. Serum glucose (12-16 hr after meal) and percentage body fat were similar in all three groups. No differences were found in organ size between the -B6 and both control groups indicating that short-term deprivation and deoxypyridoxine did not affect organ size. No significant differences were observed for serum growth hormone (GH), pituitary GH, serum prolactin (PRL), or pituitary PRL among the three groups. When meal fed, differences were minimized between B6 deprived and unrestricted control (B6) rats in body weight gain, food intake, food efficiency, and body composition.     

Influence of the subfornical organ on meal-associated drinking in rats

A lesion of the subfornical organ (SFO) may disrupt drinking after a meal of dry chow as it does drinking after intragastric administration of hypertonic saline. Food and water intakes of SFO-lesioned (SFOX) and sham-lesioned rats were measured during 90-min tests following various lengths of food deprivation. During the tests, all rats began eating before they began drinking. After 20-24 h of food deprivation, latency to begin drinking after eating had started was longer for SFOX than for sham-lesioned rats. Plasma osmolality was elevated by 2-3% in both lesion groups at 12 min, the latency for sham-lesioned rats to drink, but SFOX rats nevertheless continued eating and delayed drinking. Eating after shorter 4-h food deprivations and ad libitum feeding produced more variable drinking latencies and less consistent effects of SFO lesion. During 24 h of water deprivation, SFO lesion had no effect on the suppression of food intake and did not affect food or water intakes during the first 2 h of subsequent rehydration. These findings indicate that the SFO is involved in initiating water intake during eating and in determining drinking patterns and the amount of water ingested during a meal.     

Facilitation of cancer-associated anorexia by cholecystokinin

Cholecystokinin octapeptide (CCK-8, 5 micrograms/kg) was injected i.p. into male Sprague-Dawley rats bearing the Walker 256-carcinosarcoma, or into non-tumour bearing controls, on a 20-h food deprivation schedule. Food and water intake and body weight maintenance were monitored for 15 days after tumour implantation and compared to that of tumour-bearing animals not injected with CCK-8. Food intake was significantly reduced for the duration of the two 4-day periods of CCK-8 injection, indicating that behavioural tolerance to this peptide did not occur. The severity of anorexia and body weight loss in tumour-bearing animals was significantly greater than that observed in non-tumour bearing controls, for the first 13 days of observation. These results indicate that endogenous peptides, such as CCK, may function in tumour-bearing animals to enhance the anorexia and wasting which typifies the anorexia cachexia syndrome.     

Temporal patterning of feeding by hummingbirds

For five species of hummingbirds in the laboratory, time between meals was related to energy intake on the first meal and rate of energy expenditure between meals. Field observations gave similar results. Average meal sizes were similar at one intake rate independent of food caloric density; females averaged longer bouts than males. When rate of intake was approximately halved, meal duration approximately doubled and volume intake remained similar. We postulate that feeding is initiated when crop contents reach a lower threshold and that feeding is terminated after ingestion of an optimal volume determined by the added weight of the meal.     

NaCl concentration alters temporal patterns of drinking and eating by rats

To obtain an understanding of the role of taste in NaCl preference-aversionunder standard laboratory feeding conditions, we characterizedthe eating and drinking patterns of rats maintained on powderedfood, water, and NaCl solution. The concentration of NaCl wasvaried systematically from 0.01 to 0.4 M with a single concentrationpresent for four consecutive days. In addition to daily intake,the number and duration of ingestion bouts, and the number ofswitches between food and fluid and between water and salinewere recorded throughout the day/night cycle. The availabilityof NaCl solution did not alter the typical pattern of night-timefeeding and prandial (drinking after a meal) drinking. As shownpreviously, NaCl intake was highest for 0.15 M NaCl and declinedat both stronger and weaker concentrations. Variations in drinkingbout number and duration determined amount consumed. Drinkingbout duration was highest for 0.2 M NaCl then declining progressivelyat both stronger and weaker concentrations. The number of drinkingbouts was highest for 0.04 M NaCl, a concentration slightlyabove the adapting salivary sodium concentration, declininglinearly thereafter with stronger NaCl concentrations. The availabilityof NaCl solution influenced the amount of food consumed, aswell as the number and duration of food bouts. Food bout numberwas highest in the presence of the weakest 0.01 M NaCl solution,while food bout duration was highest in the presence of hypertonicNaCl concentrations. Most switching behavior occurred betweenmeal consumption and drinking and little between drinking fluids.When 0.01–0.08 NaCl solutions were available, the ratsdrank saline after a meal; when hypertonic 0.3–0.4 M NaClsolutions were available, they drank water after a meal. Inthe presence of intermediate NaCl concentrations (0.15–0.20),the choice of fluid consumed after a meal was more equivocalto the extent that there was increased switching between waterand saline and vice versa. The significance of these differencesin the micromolar features of eating and drinking are discussedin relationship to taste and postingestional control mechanismsof ingestion.     

Central versus peripheral opioid regulation of ingestive behavior in the domestic fowl

1. Three experiments were conducted to determine whether opioid regulation of ingestive behavior in the domestic fowl is mediated at sites within the central nervous system (CNS) or peripheral tissues. 2. Food and water intake were significantly decreased by the intramuscular (im) injection of naloxone hydrochloride (NHCl) and naloxone methobromide, which have a high and low ability, respectively, to cross the blood-brain barrier. 3. Water, but not food, intake was significantly decreased by the intracerebroventricular (ICV) injection of NHCl. However, water intake was not affected by the im injection of doses which were effective when given ICV. 4. These results suggest that in the domestic fowl there is a peripheral component to opioid regulation of food intake, while opioid regulation of water intake seems to be mediated at peripheral sites and within the CNS.     

Rates of gastric evacuation in piscivorous brown trout, Salmo trutta

SUMMARY. 1. The dry weight of food remaining in the stomachs of piscivorous trout decreased exponentially with time. Gastric evacuation rates increased exponentially with increasing temperature but were unaffected by predator size, meal size or type of fish prey.
2. Mathematical models were developed to estimate both the rate and time for the gastric evacuation of different meal sizes (expressed as dry weight), and were applicable to piscivorous trout of different sizes (length range 10–32 cm) feeding on trout fry or sticklebacks at different temperatures (range 5–18°C).
3. The wet weight of food in the stomachs also decreased exponentially with time, but evacuation rates both increased with temperature and decreased with increasing meal size; the latter relationship occurred because relative rates of water loss from a meal also decreased with increasing meal size. Use of wet or dry weights can therefore lead to different conclusions about the effect of meal size on evacuation rates.
4. When piscivorous trout were fed three consecutive meals of varying size, the models predicted the total dry weight of food left in the stomach, but not the weight remaining for each individual meal. Interactions between meals led to an increase in evacuation rates for meals consumed early in the series and a decrease in evacuation rates for later meals.
5. Evacuation rates for piscivorous trout were compared with those for trout feeding on invertebrates in an earlier study, and were close to those for caddis larvae as prey, higher than those for mealworms and lower than those for a variety of invertebrate prey. Although a great deal is now known about the daily food intake and growth rates of trout feeding on invertebrates, there is little comparable information for piscivorous trout.     

Weight of food and time required to satiate brown trout, Salmo trutta L.

Brown trout of different weights (range 8-358 g) were fed to satiation at fifteen different water temperatures (range 3.8–21.6°C. Both the weight of the trout (Wg) and the water temperature (T°C) affected the maximum weight of food (Q mg) consumed in a meal, and the relationship between the three variables was well described by a multiple regression equation which can be used to estimate the value of Q (with 95% confidence limits) for trout of different weights at different temperatures between 3.8°C and 21.6°C. The satiation time (with 95% confidence limits) can also be estimated from a multiple regression equation for trout of different weights at temperatures between 6.8°C and 18.1°C. Estimates from the multiple regression equations were applicable to a wide range of food organisms with the exception of larvae ofTenebrio molitor (mealworms). Appetite (measured by voluntary food intake) varied with temperature and was greatest between 13.3°C and 18.4°C. From comparisons with the results of other workers, it was concluded that the maximum amount of food consumed in a meal may provide sufficient calories for both the daily metabolic requirements and the daily maintenance requirements of a trout at temperatures between 3.8°C and 18.4°C, but not at temperatures above 18.4°C.     

Development of a system for individual feeding of baboons maintained in an outdoor group social environment

We developed a system that allows individual feeding of adult baboons, 8-15 years of age, maintained in an outdoor group social environment. The purpose of the system is to allow careful monitoring and control of individual diet. Baboons were housed in two group cages, 16 females and a single male in one and 12 females and a single male in the other. Baboons exited the group cage once daily and passed along a chute and over a scale into individual cages where they received their individual diets. Food intake was monitored during their 2-hour stay in the individual cages. Baboons rapidly learned to use this system. Food intake and weight were stable within 20 days. Food consumed decreased during the period of sexual receptivity. The maintenance of the group social environment allowed observations on the group's dominance structure and the relationship of dominance to food consumption. Speed of food access in the group cage was related to dominance. Dominance was not related to food consumed in individual cages. The system permits study of many variables related to behavior and food intake while still retaining critical social interactions.     

Effect of intracerebroventricular angiotensin II on body weight and food intake in adult rats

We recently reported that intracerebroventricular infusions of ANG II decreased food intake and increased energy expenditure in young rats. The aim of the present study was to determine if intracerebroventricular ANG II has similar effects in adult rats. The time course of the effect was also investigated with the idea that at earlier time points, a potential role for increased hypothalamic expression of corticotropin-releasing hormone (CRH) in the anorexia could be established. Finally, the contribution of ANG II-induced water drinking to the decrease in food intake was directly investigated. Rats received intracerebroventricular saline or ANG II using osmotic minipumps. Food intake, water intake, and body weight were measured daily. Experiments were terminated 2, 5, or 11 days after the beginning of the infusions. ANG II (approximately 32 ng.kg(-1).min(-1)) produced a transient decrease in food intake that lasted for 4-5 days although body weight continued to be decreased for the entire experiment most likely due to increased energy expenditure as evidenced by increased uncoupling protein-1 mRNA expression in brown adipose tissue. At 11 and 5 days, the expression of CRH mRNA was decreased. At 2 days, CRH expression was not suppressed even though body weight was decreased. The decrease in food intake and body weight was identical whether or not rats were allowed to increase water consumption. These data suggest that in adult rats ANG II acts within the brain to affect food intake and energy expenditure in a manner that is not related to water intake.