Increased Hunger Levels Research Articles

A randomized feasibility trial of time-restricted eating during pregnancy in people with increased risk of gestational diabetes

Time-restricted eating (TRE) is a nutritional intervention that confines the daily time-window for energy intake. TRE reduces fasting glucose concentrations in non-pregnant individuals, but whether this eating protocol is feasible and effective for glycemic control in pregnancy is unknown. The aim of this randomized controlled trial was to investigate the adherence to and effect of a 5-week TRE intervention (maximum 10 h daily eating window) among pregnant individuals at risk of gestational diabetes mellitus (GDM), compared with a usual-care control group. Participants underwent 2-h oral glucose tolerance tests and estimation of body composition, before and after the intervention. Interstitial glucose levels were continuously measured, and adherence rates and ratings of hunger were recorded daily. Thirty of 32 participants completed the trial. Participants allocated to TRE reduced their daily eating window from 12.3 (SD 1.3) to 9.9 (SD 1.0) h, but TRE did not affect glycemic measures, blood pressure, or body composition, compared with the control group. TRE increased hunger levels in the evening, but not in the morning, and induced only small changes in dietary intake. Adhering to a 5-week TRE intervention was feasible for pregnant individuals with increased risk of GDM but had no effect on cardiometabolic outcomes.

No Effect of Hunger on the Memory of Food Images and Prices

Abstract Purpose Food acquisition is an adaptive problem resolved via both physiological and psychological processes. Hunger could serve as a coordinating mechanism for these processes. When hunger increases, it may be beneficial to shift cognitive resources away from other adaptive problems and towards functions that increase the chances of acquiring food, such as memory for food information. However, there is limited research exploring the impacts of hunger on food-related memory, and the results are mixed. We conducted two studies investigating whether increased hunger levels improve memory for food images and prices – but not non-food images and prices – in image recognition and price recall tasks, respectively. Methods Study 1 was an online, observational study (N = 91) using self-reported hunger as a continuous measure. Study 2 was an in-person, between-subjects interventional study (N = 102) where participants were randomly allocated to a hungry or sated condition. We predicted that higher levels of hunger would improve participants’ ability to discriminate between food images they have and have not seen before and correctly recall food prices. Results We found no evidence of a hunger-related memory enhancement for food stimuli in either study in image recognition or price recall tasks. Conclusion Our findings contrast with older research but support more recent work, suggesting that the effect of hunger on food memory may be sensitive to study design and not as broadly generalisable as first thought.

Optimal foraging and physiological responses to the risk of predation: how fecal cortisol concentrations from trapped Allenby’s gerbil (Gerbillus andersoni allenbyi) relate to foraging under the risk of predation

We studied the influence of manipulating predation risk on Allenby’s gerbil ( Gerbillus andersoni allenbyi) held in a large, outdoor enclosure. We measured giving up densities (GUDs), apprehension, time allocation to foraging, harvest strategy (grab and go (GAG) vs. eat at tray (EAT)), and fecal cortisol concentration. First we established the time necessary for cortisol and corticosterone concentrations to change significantly from baseline after a stressful experience. To do this we collected feces from gerbils 2, 4, 6, or 8 hours after being handled (treatment) or not (control). After 8 h, fecal cortisol, but not corticosterone, concentration was significantly higher in treatment animals. We used the results from the hormone time course experiment to design the predation experiment. We used a dog, trained to harass gerbils, to increase predation risk for the gerbils. We predicted that fecal cortisol concentrations would increase directly in the face of predation risk, or indirectly, due to reduced foraging time because of perceived predation risk that, in turn, leads to increased hunger levels. As predicted, in the presence of a predator, GUDs were higher, time allocation lower, and GAG foraging was used more in treatment animals than in controls, but we found no change in apprehension. There was no difference in cortisol concentration between predator present and no-predator treatments. However, individuals that tended to have higher average fecal cortisol concentrations also tended, on average, to spend more time foraging. This indicates a relationship between stress hormones and optimal foraging. This relationship is potentially causal. While nightly changes in behavior may not be related to stress hormones, over course time scales, stress hormones may be driving gerbils to forage more.

Risky decision-making after exposure to a food-choice task in excess weight adolescents: Relationships with reward-related impulsivity and hunger.

ObjectiveTo assess the effects of exposure to a food-choice task (appetizing versus healthy food) on risky decision-making by excess versus normal weight adolescents. We also analyzed the influence of food visualization on hunger levels, as well as group differences in food choices and impulsivity.MethodsFifty-six adolescents (aged 13–18 years) classified as excess (n = 27) or normal (n = 29) weight participated in the study. Risky-decision-making was assessed through the Balloon Analogue Risk Task, which was administered before and after a food-choice task. We also evaluated impulsivity traits through the UPPS-P Scale, and subjective hunger levels with a visual analogue scale.ResultsAdolescents with excess weight showed enhanced risky decision-making after the food-choice task compared to normal weight adolescents, as well as increased hunger levels. Furthermore, excess weight adolescents made more appetizing choices, and showed greater scores for Positive Urgency and Sensation Seeking. Reward-related impulsivity measures were positively associated with the number of appetizing choices in the food-choice task. Several associations were found between impulsivity measures, hunger levels and risk-taking variables.ConclusionsExcess weight adolescents increased their risky-decision-making after food exposure and this augmentation was associated with the increase in hunger levels. Increased hunger levels and risk-taking after food exposure could lead to overeating. Alterations in decision-making caused by food signals may be a long-term risk factor for the development of obesity in adulthood. In modern societies, with the high availability and continuous exposure to food cues, decision-making may be a crucial factor in maintain healthy eating habits in adolescents.

Of Meat and Men: Sex Differences in Implicit and Explicit Attitudes Toward Meat.

Modern attitudes to meat in both men and women reflect a strong meat-masculinity association. Sex differences in the relationship between meat and masculinity have not been previously explored. In the current study we used two IATs (implicit association tasks), a visual search task, and a questionnaire to measure implicit and explicit attitudes toward meat in men and women. Men exhibited stronger implicit associations between meat and healthiness than did women, but both sexes associated meat more strongly with ‘healthy’ than ‘unhealthy’ concepts. As ‘healthy’ was operationalized in the current study using terms such as “virile” and “powerful,” this suggests that a meat-strength/power association may mediate the meat-masculinity link readily observed across western cultures. The sex difference was not related to explicit attitudes to meat, nor was it attributable to a variety of other factors, such as a generally more positive disposition toward meat in men than women. Men also exhibited an attention bias toward meats, compared to non-meat foods, while females exhibited more caution when searching for non-meat foods, compared to meat. These biases were not related to implicit attitudes, but did tend to increase with increasing hunger levels. Potential ultimate explanations for these differences, including sex differences in bio-physiological needs and receptivity to social signals are discussed.

Independent, Reciprocal Neuromodulatory Control of Sweet and Bitter Taste Sensitivity during Starvation in Drosophila

An organism's behavioral decisions often depend upon the relative strength of appetitive and aversive sensory stimuli, the relative sensitivity to which can be modified by internal states like hunger. However, whether sensitivity to such opposing influences is modulated in a unidirectional or bidirectional manner is not clear. Starved flies exhibit increased sugar and decreased bitter sensitivity. It is widely believed that only sugar sensitivity changes, and that this masks bitter sensitivity. Here we use gene- and circuit-level manipulations to show that sweet and bitter sensitivity are independently and reciprocally regulated by starvation in Drosophila. We identify orthogonal neuromodulatory cascades that oppositely control peripheral taste sensitivity for each modality. Moreover, these pathways are recruited at increasing hunger levels, such that low-risk changes (higher sugar sensitivity) precede high-risk changes (lower sensitivity to potentially toxic resources). In this way, state-intensity-dependent, reciprocal regulation of appetitive and aversive peripheral gustatory sensitivity permits flexible, adaptive feeding decisions.

Fight or flight: agonistic interactions between females of Acanthogonatus centralis Goloboff 1995 (Araneae, Mygalomorphae)

Using a resident (R)-intruder (I) paradigm, 132 encounters between female Acanthogonatus centralis were investigated in order to study its intrasexual interactions and aggressiveness. We also examined the effect of presumed increased hunger levels on the incidence of killing and cannibalism. We selected 3 groups with different satiation levels: medium group (M), low group (L), and high group (H). Interactions took place in 79.54% of the trials. Aggression by lunges or bites was observed in 21.96% of encounters. Spiders made foreleg vibrations and touched the silk, which functioned as an aggression-attenuating mechanism. Other general behaviors observed include threat behavior and hug behavior. We found significant differences between charges and retreats in the following treatments: M(R)-M(I), L(R)-L(I), H(R)-H(I), and H(R)-M(I). During encounters we observed 9 cases of cannibalism between females. Interactions were predominantly nonaggressive, at least in the resident-intruder paradigm. Intraspecific predation was not a response to presumed increased hunger. Future approaches to agonistic behavior and cannibalism should include analyses of diet characteristics over longer periods and of experience in determining the outcome of encounters between adult females.

Mixed strategies of griffon vultures' (Gyps fulvus) response to food deprivation lead to a hump-shaped movement pattern.

BackgroundThe need to obtain food is a critical proximate driver of an organism’s movement that shapes the foraging and survival of individual animals. Consequently, the relationship between hunger and foraging has received considerable attention, leading to the common conception that hunger primarily enhances a “food-intake maximization” (FIMax) strategy and intensive search. A complementary explanation, however, suggests a trade-off with precautions taken to reduce the risk of physiological collapse from starvation, under a strategy we denote as “energy-expenditure minimization” (EEMin). The FImax-EEmin trade-off may interact with the forager’s hunger level to shape a complex (non-monotonic) response pattern to increasing hunger. Yet, this important trade-off has rarely been investigated, particularly in free-ranging wild animals.We explored how hunger affects the movements of adult griffon vultures (Gyps fulvus) in southern Israel. Transmitters combining GPS and accelerometers provided high-resolution data on vultures’ movements and behavior, enabling the identification of feeding events and the estimation of food deprivation periods (FDPs, measured in days), which is used as a proxy for hunger.ResultsData from 47 vultures, tracked for 339 ± 36 days, reveal high variability in FDPs. While flight speed, flight straightness and the proportion of active flights were invariant in relation to food deprivation, a clear hump-shaped response was found for daily flight distances, maximal displacements and flight elevation. These movement characteristics increased during the first five days of the FDP sequence and decreased during the following five days. These characteristics also differed between short FDPs of up to four days, and the first four days of longer FDP sequences.These results suggest a switch from FIMax to EEMin strategies along the FDP sequence. They also indicate that vultures’ response to hunger affected the eventual duration of the FDP. During winter (the vultures’ incubation period characterized by unfavorable soaring meteorological conditions), the vultures’ FIMax response was less intensive and resulted in longer starvation periods, while, in summer, more intensive FIMax response to hunger resulted in shorter FDPs.ConclusionsOur results show a flexible, non-monotonic response of free-ranging wild animals to increasing hunger levels, reflecting a trade-off between increasing motivation to find food and the risk of starvation. The proposed trade-off offers a unifying perspective to apparently contradictory or case-specific empirical findings.Electronic supplementary materialThe online version of this article (doi:10.1186/2051-3933-1-5) contains supplementary material, which is available to authorized users.

Effects of hunger level and tube diameter on the feeding behavior of teat-fed dairy calves

Behavioral changes caused by variation in hunger have a great potential in health monitoring in dairy cattle. The present experiment used 48 Danish Holstein bull calves with a median age of 33 d. We examined the effect of different levels of hunger (reduced, in which calves were fed 1.5L of milk via esophageal tube before feeding; increased, in which calves were fed half milk ration at the previous feeding, or control, in which calves were fed normal ration at the previous feeding) on feeding behavior of calves fed via different tube diameters (6.0, 3.0, or 1.5mm). Behavior observed during a 40-min period after morning milk feeding on d 7, 9, and 11 of testing is reported. No significant interactions between tube diameter and hunger level on behavior were found. Reduced tube diameter led to increased latency to empty the teat bucket, increased duration of nutritive sucking, and decreased duration of nonnutritive sucking for calves fed via 1.5-mm tubes compared with calves in the 2 other treatments. The duration of nonnutritive sucking increased with increasing level of hunger. Furthermore, calves with reduced hunger showed a lower frequency of butting than calves at the 2 other hunger levels. The present results show that only a rather high reduction in tube diameter led to reduced drinking rate. Neither reduced nor increased hunger levels led to changes in drinking rate, but calves showed reduced nonnutritive sucking and butting when they were less hungry and increased nonnutritive sucking and butting when hunger was increased. The results suggest that nonnutritive sucking is a more sensitive indicator than drinking rate of changes in feeding motivation. Consequently, reduction in nonnutritive sucking might be a new candidate in the search for behavioral indicators of disease in dairy calves.

Low reproductive success of great tits in the preferred habitat: A role of food availability

Habitat-related variation has been revealed in the seasonal reproductive patterns of great tits inhabiting mosaics of deciduous woodland fragments and managed coniferous forests. The number and quality of offspring tend to be higher in the non-preferred coniferous habitat compared with the preferred deciduous habitat. We explored whether these patterns can be explained by variation in food abundance and/or parental provisioning ability. Frass fall seemed not to be a reliable measure of the seasonal dynamics of nestling feeding conditions, although it is widely used for this purpose. No habitat-related differences were found in the tendency of parents to increase provisioning frequency in response to increased hunger levels of nestlings, suggesting that provisioning frequency as such is not a limiting factor for nestling growth. Higher feeding rates in deciduous habitat were associated with lower proportions of high-quality food items among prey delivered to offspring. These findings confirm that relatively high nestling feeding rates in birds may reflect the low quality of available food rather than the quality of parental care or an abundance of food in the environment. The results also indicate that deciduous forest habitat, though preferred by tits, may sometimes provide poorer brood-rearing conditions than the non-preferred, coniferous habitat. We suggest that the great tit's preference for deciduous habitat, which presumably evolved in more southern regions, may be maladaptive in northern regions where deciduous woods are mainly young, secondary stands of alder and birch.

Effect of calorie restriction on subjective ratings of appetite

Energy or calorie restriction (CR) has consistently been shown to produce weight loss and have beneficial health effects in numerous species, including primates and humans. Most individuals, however, are unable to sustain weight losses induced through reductions in energy intake, potentially due to increased hunger levels. The effects that prolonged CR has on subjective aspects of appetite have not been well studied. Thus, the present study tested the effect of 6 months of caloric restriction on appetite in healthy, overweight men and women. Forty-eight overweight men and women with a body mass index (BMI; kg m(-2)) between 25-29.9 took part in a 6-month study and were randomised into one of four groups: healthy diet (control); 25% CR; 12.5% CR plus exercise (12.5% increased energy expenditure; CR + EX); low-calorie diet [LCD; 3724 kJ day(-1) (890 kcal day(-1)) until 15% of initial body weight was lost, then maintenance]. Appetite markers (i.e. hunger, fullness, desire to eat, etc.) were assessed weekly during a fasting state. Body weight was significantly reduced in all three energy-restricted groups (CR = -10.4 +/- 0.9%; CR + EX = -10.0 +/- 0.8%; and LCD = -13.9 +/-0.7%), indicating that participants were adherent to their energy restriction regimen, whereas the healthy diet control group remained weight stable (control = -1.0 +/- 1.1%). Despite these significant weight losses, appetite ratings of participants in the three energy-restricted groups at month 6 were similar to the weight stable control group. CR regimens with low fat diets producing significant weight losses have similar effects on appetite markers over a 6-month time period compared to a weight stable control group.

Hunger, light level and body size affect refuge use by post‐settlement lingcod Ophiodon elongatus

Using experimental methods, body size, nutritional state (hunger) and light level were investigated as possible determinants of the extent to which juvenile lingcod Ophiodon elongatus used structural refuges. In the laboratory, older, larger individuals (134–162 mm total length, LT) exhibited a higher propensity for structure use than did smaller juvenile fish (78–103 mm LT). In fish of both body sizes, increasing hunger levels caused fish to emerge more readily from refuges than satiated individuals, with this effect most prominent for smaller fish. Diel patterns of ambient illumination were simulated in the laboratory, and refuge use by large individuals decreased significantly in response to lower nocturnal light levels, a pattern that was not observed in the smaller size class. These results indicate an ontogenetic shift in refuge use. During the summer, as post‐settlement fish grew larger, they tended to increase affinity for structurally complex habitat, and also showed divergent patterns of behaviour in relation to hunger and light level.

Honesty in host‐parasite communication signals: the case for begging by fledgling brown‐headed cowbirds Molothrus ater

Nestling parasites typically beg more intensively than do host nestlings yet these exaggerated displays are also honest in that they are modulated by hunger and age. We hypothesized that honesty was also maintained in the food solicitation behaviors of fledgling brood parasites because the benefits and costs of their begging displays are similar to those of nestling parasites. Begging displays of hand‐reared 14–32 days old brown‐headed cowbirds Molothrus ater that had experimentally manipulated nutritional needs were recorded to analyze variation in the peak frequency, duration, and rate of fledglings’ begging bouts. Peak frequency of bouts decreased with greater age and was lower for females. Bout rate was greater with increasing hunger levels of fledgling parasites but did not vary with age. Consistent and predictable variation of acoustic begging displays with age, sex, and hunger‐level indicates honesty in host‐parasite communication systems through conveying truthful information about the many possible needs of parasitic fledglings.

The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum.

Previous studies have examined abiotic and biotic factors that facilitate agonistic behavior. For larval amphibians, food availability and conspecific density have been suggested as important factors influencing intraspecific aggression and cannibalism. In this study, we examined the separate and combined effects of food availability and density on the agonistic behavior and life history of larval long-toed salamanders, Ambystoma macrodactylum. We designed a 2×2 factorial experiment in which larvae were raised with either a high or low density of conspecifics and fed either a high or low level of food. For each treatment, we quantified the amount of group size variation, biting, and cannibalism occurring. Additionally, we examined survival to, time to and size at metamorphosis for all larvae. Results indicated that differences in both density and food level influenced all three life history traits measured. Moreover, differences in food level at which larvae were reared resulted in higher within-group size variation and heightened intraspecific biting while both density and food level contributed to increased cannibalism. We suggest that increased hunger levels and an uneven size structure promoted biting among larvae in the low food treatments. Moreover, these factors combined with a higher encounter rate with conspecifics in the high density treatments may have prompted larger individuals to seek an alternative food source in the form of smaller conspecifics.

Quantifying food limitation of arthropod predators in the field.

A method for quantifying food limitation of arthropod predators in the field is presented and applied to species of ground beetles (Carabidae) and sheet-web spiders (Linyphiidae) from a cereal field. Food limitation is expressed quantitatively as accumulated hunger (=starvation) by transforming 24-h food consumption at 20°C of animals newly collected in the field into days of starvation at 20°C. This is done by means of a reference curve relating 24-h food intake at 20°C to starvation periods (days) at 20°C. Such a reference curve was obtained for the carabid beetle Agonum dorsale in the laboratory. For other species the reference curve was modified with species-specific data. The procedure makes it possible to compare the feeding conditions of different species populations that are part of the same community. Hunger levels in the field for females of A.␣dorsale were equivalent to c. 15 days of starvation in early spring, c. 5 days in June, increasing to c. 10 days in late summer. Two ground beetles occurring during summer also showed increasing hunger levels from June to July, probably the result of a dry summer. Two spider species experienced a hunger level in the range of 4-8 days of starvation.

Searching Behaviour of Two Coccinellid Predators, Coccinella transversalis Fab. and Cheilomenes sexmaculatus Fab., on Egg Plant Infested with Aphis gossypii Glov.

The searching behaviour of two coccinellid predators, Coccinella transversalis Fab. and Cheilomenes (Menochilus) sexmaculatus Fab. at different hunger levels and larval stage was studied on eggplant infested with Aphis gossypii Glov. Females of both predators required more prey to return to a state of complete satiation. As the period of starvation increased, more aphids were consumed by both the beetles, reaching a maximum at 24 h starvation. In first, second, third and fourth instars of both the predators, the searching time and the number of eggplant leaf veins visited increased with increasing hunger levels. A high positive correlation between searching time and hunger level of tested predators was obtained.

Diet and Feeding Behavior of the Solpugid, EremobatesPalpisetulosus (Solpugida: Eremobatidae)

Eremobates palipsetulosus is a generalist predator which preys upon a wide variety of arthropods and seems to prefer smaller, soft‐bodied prey items. Spiders as welt as orthopteran, lepidopteran and coleopteran insects comprise 76% of the total diet. When a prey item is encountered, the palpi are used to pull the prey toward the chelicerae. The prey is then grasped in the chelicerae which are used to fragment and grind the prey tissues for subsequent ingestion. Increased hunger levels result in significantly faster ingestion time and higher capture rates. This is the first quantitative study on prey capture and feeding behavior for solpugids.

Grazing catfish, fishing birds, and attached algae in a Panamanian stream

In streams where algivorous fishes abound, striking variation of attached algae often develops along depth gradients, with bands of high standing crops in shallow water ( 20 cm) water, algae were rapidly consumed by grazing catfish. Catfish were removed from three stream pools and left in place in three control pools. Ten days after catfish removal, algal standing crops in deep and shallow areas of removal pools were similar, while algal standing crops were higher in shallow than in deep areas of control pools. Catfish were exposed to fishing birds in open-topped enclosures. In one of three series of these pens, most catfish in shallow pens (10 and 20 cm) disappeared after 14 days, while catfish in deeper pens (30 and 50 cm) did not. Other groups of catfish which were caged 8 days showed differences in behavior depending on whether they had been fed or starved. After their release into their home pool, starved catfish spent more time feeding than did fed catfish. Despite their apparently increased hunger levels, starved catfish did not venture into shallow water to obtain algae. These results support the view that predator induced avoidance by grazers of certain areas can produce spatial pattern in the flora of flowing water communities.