Episodic Memory and Appetite Regulation in Humans

Psychological and neurobiological evidence implicates hippocampal-dependent memory processes in the control of hunger and food intake. In humans, these have been revealed in the hyperphagia that is associated with amnesia. However, it remains unclear whether ‘memory for recent eating’ plays a significant role in neurologically intact humans. In this study we isolated the extent to which memory for a recently consumed meal influences hunger and fullness over a three-hour period. Before lunch, half of our volunteers were shown 300 ml of soup and half were shown 500 ml. Orthogonal to this, half consumed 300 ml and half consumed 500 ml. This process yielded four separate groups (25 volunteers in each). Independent manipulation of the ‘actual’ and ‘perceived’ soup portion was achieved using a computer-controlled peristaltic pump. This was designed to either refill or draw soup from a soup bowl in a covert manner. Immediately after lunch, self-reported hunger was influenced by the actual and not the perceived amount of soup consumed. However, two and three hours after meal termination this pattern was reversed - hunger was predicted by the perceived amount and not the actual amount. Participants who thought they had consumed the larger 500-ml portion reported significantly less hunger. This was also associated with an increase in the ‘expected satiation’ of the soup 24-hours later. For the first time, this manipulation exposes the independent and important contribution of memory processes to satiety. Opportunities exist to capitalise on this finding to reduce energy intake in humans.     

Effects of fat, protein, and carbohydrate and protein load on appetite, plasma cholecystokinin, peptide YY, and ghrelin, and energy intake in lean and obese men

While protein is regarded as the most satiating macronutrient, many studies have employed test meals that had very high and unsustainable protein contents. Furthermore, the comparative responses between lean and obese subjects and the relationships between energy intake suppression and gut hormone release remain unclear. We evaluated the acute effects of meals with modest variations in 1) fat, protein, and carbohydrate content and 2) protein load on gastrointestinal hormones, appetite, and subsequent energy intake in lean and obese subjects. Sixteen lean and sixteen obese men were studied on four occasions. Following a standardized breakfast, they received for lunch: 1) high-fat (HF), 2) high-protein (HP), 3) high-carbohydrate/low-protein (HC/LP), or 4) adequate-protein (AP) isocaloric test meals. Hunger, fullness, and gut hormones were measured throughout, and at t = 180 min energy intake at a buffet meal was quantified. In lean subjects, hunger was less and fullness greater following HF, HP, and AP compared with HC/LP meals, and energy intake was less following HF and HP compared with HC meals (P < 0.05). In the obese subjects, hunger was less following HP compared with HF, HC/LP, and AP meals, and energy intake was less following HP and AP compared with HF and HC meals (P < 0.05). There were no major differences in hormone responses to the meals among subject groups, but the CCK and ghrelin responses to HP and AP were sustained in both groups. In conclusion, HP meals suppress energy intake in lean and obese subjects, an effect potentially mediated by CCK and ghrelin, while obese individuals appear to be less sensitive to the satiating effects of fat.     

Mode of consumption plays a role in alleviating hunger and thirst

While studying the effect of structure on satiety, effects of mode of consumption, additional water to drink, and thirst have been neglected. The objective was to assess effects of structure, mode of consumption of food, and additional drinking of water on fullness and thirst. In study 1, 20 subjects (BMI 22.5 ± 0.5 kg/m(2); age 21.4 ± 3 years) underwent consumption conditions; SEW: solids to eat + 750 ml water to drink; LEW: liquefied soup to eat including 500 ml water + 250 ml water separately to drink; LDW: the same as LEW but served as drinks; SE, LE, and LD: the same as previous but without water to drink. In study 2, a subset of subjects underwent consumption conditions: solid carbohydrate, solid protein, solid fat: the same as SEW, but for each macronutrient separately; liquefied carbohydrate, liquefied protein, liquefied fat: the same as LEW, but for each macronutrient separately. Appetite, insulin concentration, glucose concentration, and ghrelin concentration were measured. Eating, independent of structure, suppressed desire to eat more than drinking (P < 0.01). Drinking water separately vs. water consumption in the food suppressed thirst more (P < 0.001). Regarding protein, satiety was higher in the solid vs. liquefied condition, while blood parameters were not significantly different. Only after drinking a meal most subjects (80%) wanted to consume more of the same meal, in order to alleviate hunger (63%) or quench thirst (37%). We conclude that mode of consumption plays a role in alleviating hunger and thirst. Subjects required further consumption after drinking the meal, motivated by hunger or thirst, showing that drinking a meal causes confusion that may imply a risk of overconsumption.     

Loxiglumide, a CCK-A receptor antagonist, stimulates calorie intake and hunger feelings in humans

Exogenous cholecystokinin (CCK) induces early satiety when infused into humans. Whether alimentary CCK (CCK-A) receptor blockade stimulates food intake in humans is, however, uncertain. The aim of the present investigation was, therefore, to establish the effect of CCK-A receptor blockade on satiety and eating behavior in healthy volunteers. To further explore the role of endogenous CCK, the effects of the specific CCK-A receptor antagonist loxiglumide (Lox; 22 micromol. kg(-1). h(-1)) on satiety and eating behavior were investigated in healthy men and compared with saline infusions (as placebo) in a series of randomized, double-blind, placebo-controlled, crossover studies. Lox produced a slight (7%), but not significant (P = 0.104), increase in food intake that was accompanied by a modest (10%), but significant (P < 0.004), increase in calorie intake. Fluid ingestion was not affected by Lox. Subjects experienced more hunger and delayed fullness during Lox infusion than during saline infusion (P < 0.05). This study provides further evidence that CCK is an endogenous physiological satiety signal acting through CCK-A receptor-mediated mechanisms. Repeated-dose studies comparing hunger and satiety responses after CCK-A receptor blockade in healthy subjects and patients with eating disorders may help clarify the possible involvement of endogenous CCK in these conditions.     

Slow Food: Sustained Impact of Harder Foods on the Reduction in Energy Intake over the Course of the Day

Background

Previous research has shown that oral processing characteristics like bite size and oral residence duration are related to the satiating efficiency of foods. Oral processing characteristics are influenced by food texture. Very little research has been done on the effect of food texture within solid foods on energy intake.

Objectives

The first objective was to investigate the effect of hardness of food on energy intake at lunch, and to link this effect to differences in food oral processing characteristics. The second objective was to investigate whether the reduction in energy intake at lunch will be compensated for in the subsequent dinner.

Design

Fifty subjects (11 male, BMI: 21±2 kg/m², age: 24±2 y) participated in a cross-over study in which they consumed ad libitum from a lunch with soft foods or hard foods on two separate days. Oral processing characteristics at lunch were assessed by coding video records. Later on the same days, subjects consumed dinner ad libitum.

Results

Hard foods led to a ∼13% lower energy intake at lunch compared to soft foods (P<0.001). Hard foods were consumed with smaller bites, longer oral duration per gram food, and more chewing per gram food compared to the soft foods (P<0.05). Energy intake at dinner did not differ after both lunches (P = 0.16).

Conclusions

Hard foods led to reduced energy intake compared to soft foods, and this reduction in energy intake was sustained over the next meal. We argue that the differences in oral processing characteristics produced by the hardness of the foods explain the effect on intake. The sustained reduction in energy intake suggests that changes in food texture can be a helpful tool in reducing the overall daily energy intake.     

Effects of energy content and energy density of pre-portioned entrées on energy intake

Pre-portioned entrées are commonly consumed to help control portion size and limit energy intake. The influence of entrée characteristics on energy intake, however, has not been well studied. We determined how the effects of energy content and energy density (ED, kcal/g) of pre-portioned entrées combine to influence daily energy intake. In a crossover design, 68 non-dieting adults (28 men and 40 women) were provided with breakfast, lunch, and dinner on 1 day a week for 4 weeks. Each meal included a compulsory, manipulated pre-portioned entrée followed by a variety of unmanipulated discretionary foods that were consumed ad libitum. Across conditions, the entrées were varied in both energy content and ED between a standard level (100%) and a reduced level (64%). Results showed that in men, decreases in the energy content and ED of pre-portioned entrées acted independently and added together to reduce daily energy intake (both P < 0.01). Simultaneously decreasing the energy content and ED reduced total energy intake in men by 16% (445 ± 47 kcal/day; P < 0.0001). In women, the entrée factors also had independent effects on energy intake at breakfast and lunch, but at dinner and for the entire day the effects depended on the interaction of the two factors (P < 0.01). Simultaneously decreasing the energy content and ED reduced daily energy intake in women by 14% (289 ± 35 kcal/day; P < 0.0001). Both the energy content and ED of pre-portioned entrées affect daily energy intake and could influence the effectiveness of such foods for weight management.     

Mechanisms behind the portion size effect: visibility and bite size

Increases in portion size lead to increases in energy intake, yet the mechanisms behind this "portion size effect" are unclear. This study tested possible mechanisms of the portion size effect, i.e., bite size and visual cues. A 2 × 2 repeated measures, within-subject design was used to test the effects of portion size (410 g vs. 820 g of a pasta dish) and visual cues (blindfolded vs. visible) on energy intake in 30 individuals (15 men, 15 women). At each meal participants were exposed to one of four experimental conditions (small portion/visible; small portion/blindfold; large portion/visible; large portion/blindfold). Participant characteristics, food intake, number of bites, meal duration, palatability measures and hunger and fullness were assessed. In response to a doubling of the portion presented, entrée energy intake increased 26% (220 kcal; P < 0.001) and mean bite size increased 2.4 g/bite (P < 0.05). Overweight (OW) individuals consumed 40% (334 kcal) more of the entrée in response to the large portion condition (P < 0.05), while lean individuals' intakes did not differ (P < 0.56). A 12% (122 kcal) decrease in entrée intake was observed in the blindfolded condition (P < 0.01), but no portion by visual cue interaction was found; indicating that blindfolding did not significantly attenuate the portion size effect. These data suggest that the portion size effect is not impacted by removing the visual cue of food and that this effect occurs via changes in bite size in adults.     

Increased Carbohydrate Induced Ghrelin Secretion in Obese vs. Normal‐weight Adolescent Girls

Orexigenic and anorexigenic pathways mediate food intake and may be affected by meal composition. Our objective was to determine whether changes in levels of active ghrelin and peptide YY (PYY) differ in obese vs. normal‐weight adolescent girls following specific macronutrient intake and predict hunger and subsequent food intake. We enrolled 26 subjects: 13 obese and 13 normal‐weight girls, 12–18 years old, matched for maturity (as assessed by bone age) and race. Subjects were assigned a high‐carbohydrate, high‐protein, and high‐fat breakfast in random order. Active ghrelin and PYY were assessed for 4 h after breakfast and 1 h after intake of a standardized lunch. Hunger was assessed using a standardized visual analog scale (VAS). No suppression in active ghrelin levels was noted following macronutrient intake in obese or normal‐weight girls. Contrary to expectations, active ghrelin increased in obese girls following the high‐carbohydrate breakfast, and the percent increase was higher than in controls (P = 0.046). Subsequent food intake at lunch was also higher (P = 0.03). Following the high‐fat breakfast, but not other breakfasts, percent increase in PYY was lower (P = 0.01) and subsequent lunch intake higher (P = 0.005) in obese compared with normal‐weight girls. In obese adolescents, specific intake of high‐carbohydrate and high‐fat breakfasts is associated with greater increases in ghrelin, lesser increases in PYY, and higher intake at a subsequent meal than in controls. Changes in anorexigenic and orexigenic hormones in obese vs. normal‐weight adolescents following high‐carbohydrate and high‐fat meals may influence hunger and satiety signals and subsequent food intake.     

Effects of food texture change on metabolic parameters: short- and long-term feeding patterns and body weight

A complete diet was prepared with cooked pieces of meat, beans, cream starch, and water and presented to the rats in two different textures: a blended purée and a rough mixture that required a lot of chewing. We hypothesized that this texture modification might change both anticipatory reflexes and feeding behavior. Feeding rate, meal size, intermeal intervals, and their correlation were monitored in response to each texture. The long-term (6 wk) effect on body weight was assessed. Periprandial plasma glucose, insulin, glucagon, and lipid concentrations were assayed. Whole and background metabolism, respiratory quotient, and locomotion were measured using a computerized calorimeter of original design. In the short term, rats preferred the mixture. However, after 3 wk, they ingested more purée than mixture and gained more body weight per gram of food ingested as purée. Insulin response declined earlier with the mixture. During meals, glycerol and free fatty acid increased earlier with purée, whereas in the postprandial period, glycerol increased earlier with mixture. The metabolic rate, however, was not significantly affected. We concluded that texture, an everyday manipulation performed on food for human consumption, affects not only palatability of ingestants but also their metabolic management in the short and long term.     

Interaction between CCK and a preload on reduction of food intake is mediated by CCK-A receptors in humans

Cholecystokinin (CCK) interacts with neural signals to induce satiety in several species, but the mechanisms are unclear. We therefore tested the hypothesis that alimentary CCK (CCK-A) receptors mediate the interaction of CCK with an appetizer on food intake in humans. CCK octapeptide (CCK-8, 0.75 microgram infused over 10 min) or saline (placebo) with concomitant infusions of saline (placebo) or loxiglumide, a specific CCK-A antagonist, was infused into 16 healthy men with use of a double-blind, four-period design. All subjects received a standard 400-ml appetizer (amounting to 154 kcal) but were free to eat and drink thereafter as much as they wished. The effect of these infusions on feelings of hunger and satiety and on food intake was quantified. CCK-8 induced a reduction in calorie intake (P < 0.05) compared with saline. Furthermore, a decrease in hunger feelings (P < 0.05, saline-CCK-8 vs. all other treatments) and an increase in fullness were observed. These effects were antagonized for hunger and fullness by loxiglumide. We conclude that CCK-8 interacts with an appetizer to modulate satiety in humans. These effects are mediated by CCK-A receptors.     

Ineffectiveness of ceruletide to reduce food intake and body weight in obese women hospitalized for weight reduction and treated with a restricted diet. A double-blind study

Ceruletide is a synthetic decapeptide closely resembling the 8-carboxy-terminal peptide of cholecystokinin (CCK-8) with which it shares several biological properties. In a double-blind study versus placebo, we evaluated the effects of ceruletide on self-rated hunger and food intake at lunch time, as well as on body weight in 14 obese women hospitalized for weight reduction and on a restricted diet. During two 6-day courses of treatment with ceruletide or placebo, ceruletide 0.3 microgram/kg b.wt. or an equivalent volume of its diluent were injected IM at 11.30 a.m., i.e., 30 min before lunch. Feelings of hunger were quantitated, using a visual analogue self-rating scale, prior to the injection of ceruletide or placebo and 30 min thereafter, i.e., just prior to the start of meal ingestion, as well as 2 hr after the start of the meal. Duration and caloric content of food ingested at lunch, as well as morning body weight, were recorded daily. Ceruletide, compared to placebo, did not significantly influence any of the above variables. However, in the first three experimental days, the increase in self-rated hunger from values before the injection to 30 min thereafter was less marked, though not significantly so (0.05 less than p less than 0.1), with ceruletide than with placebo. Thus, it appears that ceruletide, under the experimental conditions of the present study, was not effective in enhancing the patients' motivation to lose weight and to further restrict their food intake at lunch time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Food Form and Portion Size Affect Postprandial Appetite Sensations and Hormonal Responses in Healthy,Nonobese, Older Adults

Data are limited concerning the dietary factors that influence appetite control in older adults. This study examined the effects of food form and portion size on appetite in 43 older adults (age: 72 ± 1 years; BMI: 25.6 ± 0.3 kg/m²). Subjects were assigned to groups based on portion size of the test meal (12.5% (n = 18) vs. 25% (n = 25) of estimated energy need). Subjects randomly consumed, on two separate days, the respective solid or beverage test meal. Appetite sensations and hormonal responses were measured over 4 h. Main effects of food form (P < 0.05) and/or portion size (P < 0.05) were observed for each appetite sensation. Postprandial hunger and desire to eat were greater following beverage vs. solid meal (between 12.5% vs. 25%), whereas fullness was lower after beverage vs. solid meal (P < 0.05). Main effects of food form and/or portion size were observed for glucose, insulin, and ghrelin. Postprandial glucose and insulin concentrations were lower after beverage vs. solid meal (between 12.5% vs. 25%; all comparisons, P < 0.05) whereas beverage meal led to greater 4‐h ghrelin vs. solid meal (P = 0.09). No main effects were observed for glucagon‐like peptide‐1 (GLP‐1) or cholecystokinin (CCK). When adjusting for age, food form remained significant for postprandial hunger and fullness; portion size remained significant for postprandial glucose. Greater hunger and reduced satiety with accompanying glucose, insulin, and ghrelin following the beverage vs. solid meals, and to some extent, in smaller vs. larger portions suggest that appetite control is influenced by food form and portion size in older adults. These findings may enhance the development of appropriate dietary strategies that help to regulate energy balance.     

Original Articles 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 HI). 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.     

Heritability of hyperphagic eating behavior and appetite-related hormones among Hispanic children

Objective: Eating in the absence of hunger (EAH) may be a genetically influenced phenotype of overweight children, but evidence is limited. This research evaluated the heritability (h²) of EAH and its association with overweight among Hispanic children 5 to 18 years old. Genetic and environmental associations of EAH with overweight, fat mass, and key hormonal regulators of food intake were also evaluated. Research Methods and Procedures: A family design was used to study 801 children from 300 Hispanic families. Weighed food intakes were used to measure EAH after an ad libitum dinner providing 50% of estimated energy needs. Fasting ghrelin, amylin, insulin, and leptin were measured by immunoassays. Measured heights, weights, and fat mass (using DXA) were obtained. Total energy expenditure (TEE) was measured by room respiration calorimetry. Results: On average, children consumed 41% of TEE at the dinner meal, followed by an additional 19% of TEE in the absence of hunger. Overweight children consumed 6.5% more energy at dinner (p < 0.001) and 14% more energy in the absence of hunger (p < 0.001) than non‐overweight children. Significant heritabilities were seen for EAH (h² = 0.51) and dinner intake (h² = 0.52) and for fasting levels of ghrelin (h² = 0.67), amylin (h² = 0.37), insulin (h² = 0.37), and leptin (h² = 0.34). Genetic correlations were seen between eating behavior and fasting hormones, suggesting common underlying genes affecting their expression. Discussion: This research provides new evidence that overweight Hispanic children exhibit elevated levels of hyperphagic eating behaviors that are influenced by genetic endowment.     

Characterization of the diurnal rhythm of peptide YY and its association with energy balance parameters in normal-weight premenopausal women

PYY may play a role in modulating satiety and energy expenditure; increasing PYY postprandially has been studied largely in single-meal responses. The diurnal rhythm of PYY and its role in energy balance have not been fully characterized. The purpose of our study was to characterize features of the diurnal rhythm of PYY and determine its role in regulating energy balance. This study was a cross-sectional analysis of 11 subjects in whom 24-h repeated blood sampling was conducted at baseline of a larger prospective study. Breakfast (B), lunch (L), dinner (D), and a snack (S) occurred between 0900 and 1900. Total PYY was assayed every hour from 0800 to 1000, every 20 min from 1000 to 2000, and every hour from 2000 to 0800. PYY variables included total AUC, postprandial peaks, and 24-h mean. Energy balance variables included energy intake, RMR, RQ, and NEAT. PYY postprandial peaks were significantly higher than fasting (P < 0.05). Twenty-four-hour peak PYY occurred after L and was significantly higher than all other peaks (P < 0.05). A cubic curve function accounted for most of the variance in PYY (r(2) = 69.9%, P < 0.01). Fasting PYY (0800) correlated with postprandial peaks at B (r = 0.77, P = 0.01), L (r = 0.71, P = 0.01), and D (r = 0.65, P = 0.03). The only significant association between PYY and energy expenditure was that RMR (kcal/24 h) correlated with 24-h mean PYY (r = 0.71, P = 0.013) and total AUC (r = 0.69, P = 0.019). We conclude that PYY displays a meal-driven diurnal rhythm and is correlated to RMR, a major contributor to energy expenditure. Thus, PYY varies in accordance with energy content and RMR, supporting a role for PYY in energy balance modulation.     

Twenty-four-hour ghrelin is elevated after calorie restriction and exercise training in non-obese women

Objective: The purpose of this study was to determine whether chronic energy deficiency achieved with caloric restriction combined with exercise is associated with changes in the 24‐hour profile of ghrelin in non‐obese, pre‐menopausal women. Research Methods and Procedures: Twelve non‐obese (BMI = 18 to 25 kg/m²), non‐exercising women (age, 18 to 24 years) were randomly assigned to a non‐exercising control group or a diet and exercise group. The 3‐month diet and exercise intervention yielded a daily energy deficit of ?45.7 ± 12.4%. Serial measurements were made of body composition, energy balance, and feelings of fullness. Repeated blood sampling over 24 hours to measure ghrelin occurred before and after the study. Results: Significant decreases in body weight, body fat, and feelings of fullness were observed in only the energy‐deficit group (p < 0.05); significant changes in the following ghrelin features were found in only the deficit group (p < 0.05): elevations in baseline (+353 ± 118 pg/mL), lunch peak (+370 ± 102 pg/mL), dinner peak (+438 ± 149 pg/mL), nocturnal rise (+269 ± 77 pg/mL), and nocturnal peak (+510 ± 143 pg/mL). In addition, we found a larger dinner decline (?197 ± 52 pg/mL) and negative correlations between changes in the ghrelin dinner profile and changes in body weight (R = 0.784), 24‐hour intake (R = 0.67), energy deficiency (R = 0.762), and feelings of fullness (R = 0.648; p < 0.05). Discussion: Changes in ghrelin concentrations across the day after weight loss are closely associated with other physiological adaptations to energy deficiency, further supporting the role of ghrelin as a countermeasure to restore energy balance.     

The 24-h energy intake of obese adolescents is spontaneously reduced after intensive exercise: a randomized controlled trial in calorimetric chambers

Background

Physical exercise can modify subsequent energy intake and appetite and may thus be of particular interest in terms of obesity treatment. However, it is still unclear whether an intensive bout of exercise can affect the energy consumption of obese children and adolescents.

Objective

To compare the impact of high vs. moderate intensity exercises on subsequent 24-h energy intake, macronutrient preferences, appetite sensations, energy expenditure and balance in obese adolescent.

Design

This randomized cross-over trial involves 15 obese adolescent boys who were asked to randomly complete three 24-h sessions in a metabolic chamber, each separated by at least 7 days: (1) sedentary (SED); (2) Low-Intensity Exercise (LIE) (40% maximal oxygen uptake, VO₂max); (3) High-Intensity Exercise (HIE) (75%VO₂max).

Results

Despite unchanged appetite sensations, 24-h total energy intake following HIE was 6–11% lower compared to LIE and SED (p<0.05), whereas no differences appeared between SED and LIE. Energy intake at lunch was 9.4% and 8.4% lower after HIE compared to SED and LIE, respectively (p<0.05). At dinner time, it was 20.5% and 19.7% lower after HIE compared to SED and LIE, respectively (p<0.01). 24-h energy expenditure was not significantly altered. Thus, the 24-h energy balance was significantly reduced during HIE compared to SED and LIE (p<0.01), whereas those of SED and LIE did not differ.

Conclusions

In obese adolescent boys, HIE has a beneficial impact on 24-h energy balance, mainly due to the spontaneous decrease in energy intake during lunch and dinner following the exercise bout. Prescribing high-intensity exercises to promote weight loss may therefore provide effective results without affecting appetite sensations and, as a result, food frustrations.

Trial Registration

ClinicalTrial.gov {"type":"clinical-trial","attrs":{"text":"NCT01036360","term_id":"NCT01036360"}}NCT01036360     

Plasma ghrelin levels and hunger scores in humans initiating meals voluntarily without time- and food-related cues

Ghrelin is an orexigenic hormone that is implicated in meal initiation, in part because circulating levels rise before meals. Because previous human studies have examined subjects fed on known schedules, the observed preprandial ghrelin increases could have been a secondary consequence of meal anticipation. A causal role for ghrelin in meal initiation would be better supported if preprandial increases occurred before spontaneously initiated meals not prompted by external cues. We measured plasma ghrelin levels among human subjects initiating meals voluntarily without cues related to time or food. Samples were drawn every 5 min between a scheduled lunch and a freely requested dinner, and hunger scores were obtained using visual analog scales. Insulin, glucose, fatty acids, leptin, and triglycerides were also measured. Ghrelin levels decreased shortly after the first meal in all subjects. A subsequent preprandial increase occurred over a wide range of intermeal intervals (IMI; 320-425 min) in all but one subject. Hunger scores and ghrelin levels showed similar temporal profiles and similar relative differences in magnitude between lunch and dinner. One subject displayed no preprandial ghrelin increase and was also the only individual whose insulin levels did not return to baseline between meals. This finding, along with a correlation between area-under-the-curve values of ghrelin and insulin, suggests a role for insulin in ghrelin regulation. The preprandial increase of ghrelin levels that we observed among humans initiating meals voluntarily, without time- or food-related cues, and the overlap between these levels and hunger scores are consistent with a role for ghrelin in meal initiation.     

Reductions in entrée energy density increase children's vegetable intake and reduce energy intake

The energy density (ED; kcal/g) of an entrée influences children's energy intake (EI), but the effect of simultaneously changing both ED and portion size of an entrée on preschool children's EI is unknown. In this within-subject crossover study, 3- to 5-year-old children (30 boys, 31 girls) in a daycare facility were served a test lunch once/week for 4 weeks. The amount and type of vegetables and cheeses incorporated into the sauce of a pasta entrée were manipulated to create two versions that varied in ED by 25% (1.6 or 1.2 kcal/g). Across the weeks, each version of the entrée was served to the children in each of two portion sizes (400 or 300 g). Lunch, consumed ad libitum, also included carrots, applesauce, and milk. Decreasing ED of the entrée by 25% significantly (P<0.0001) reduced children's EI of the entrée by 25% (63.1+/-8.3 kcal) and EI at lunch by 17% (60.7+/-8.9 kcal). Increasing the proportion of vegetables in the pasta entrée increased children's vegetable intake at lunch by half of a serving of vegetables (P<0.01). Decreasing portion size of the entrée by 25% did not significantly affect children's total food intake or EI at lunch. Therefore, reducing the ED of a lunch entrée resulted in a reduction in children's EI from the entrée and from the meal in both portion size conditions. Decreasing ED by incorporating more vegetables into recipes is an effective way of reducing children's EI while increasing their vegetable intake.     

Food limitation and starvation independently affect predator macronutrient selection

Predators are often food limited in their habitat, and some are limited by specific macronutrients (protein, lipid or carbohydrate). It is unresolved, however, to what extent and in what way food and macronutrient limitation are connected. Using a carabid beetle (Nebria brevicollis), we compared macronutrient self-selection of the animals three times: immediately after collection in the field, after being fed to satiation and nutritional balance and after a subsequent period of starvation. Both sexes were food and females lipid limited in the field; after 7–21 days of starvation both sexes increased proportional carbohydrate intake significantly. Thus, starvation created a nutrient deficit that was different from what the animals had experienced in the field. We conclude that while macronutrient limitation in nature may be influenced by hunger due to food limitation, this is not its main determinant. A nutritional imbalance of available food may override this effect.