Factors Associated with Food Intake in Passengers on LONG-HAUL FLIGHTS

To understand better how disruption to daily routines and circadian factors affect food intake, some aspects of 361 passengers' eating habits during long‐haul flights across eight time zones were investigated. Two meals were provided during each flight. Passengers stated whether or not they had eaten part or all of each meal and the reasons for this decision. They were also asked to give their responses to it (appetite beforehand, enjoyment during the meal, and satiety afterwards), and the type of meal they would prefer to have eaten, given an unrestricted choice. There were few occasions (<6%) when a meal was refused altogether, and no single reason was dominant. Subjective responses to food intake were more positive when larger meals were eaten and “appetite” rather than “no choice” was given as the reason for eating. Subjective responses were also more positive in those who thought the size of the meal offered was neither too small nor too large. When the two meals were considered separately, the first meal was well received by the passengers, and their enjoyment of it was not significantly different from “normal.” The second meal (offered soon before landing in the new time zone) was less well received, and many passengers would have preferred a smaller meal. The findings contribute to an understanding of the factors determining the decision to eat a meal and the subjective responses to the food that is eaten. They also have implications for airlines wishing to provide food that is acceptable to passengers and for those providing meals for night workers.     

Lack of evidence for a marked endogenous component determining food intake in humans during forced desynchrony

In an attempt to investigate the relative importance of endogenous and exogenous factors in determining food intake, 14 healthy subjects were studied while living in an Isolation Unit (where external time cues were absent) for eighteen 28 h "days" (equal to 21 solar days). The subjects were free to spend their waking time as they chose, and they had a free choice of what they ate and when they ate it. The only restrictions were that no naps were allowed in the "daytime," that some time was required to perform a variety of tests at regular intervals throughout the 18.67 h waking periods, and that any food preparation had to be performed by the subjects themselves. Core (rectal) temperature and activity were monitored throughout, and the subjects answered a questionnaire on their eating habits at 3 h intervals during the waking periods. The questionnaire investigated reasons for eating or not eating a meal during the previous 3 h and, if a meal had been eaten, its type, the factors influencing that choice, and the subjects' subjective responses (hunger before, enjoyment during, and satiety after) to it. The results were analyzed (two-way ANOVA) in terms of both the imposed day length (the exogenous component) and the free-running period of the temperature rhythm (the endogenous component). Results indicated that by far the main reason for eating/not eating was hunger/lack of hunger rather than factors such as food availability and time-pressure. There were statistically significant effects of time within the imposed waking periods upon the type of meal eaten--"breakfast" tending to be a snack, "lunch" a small hot meal, and the "evening meal" a large hot meal. Hot meals (whether small or large) were associated with more hunger before the meal, more enjoyment of the meal, and a greater degree of satiety afterward than were cold meals. These effects suggest that the individuals adjusted their eating habits to fit in with the imposed wake times. By contrast, the effect of circadian phase upon food intake, the type of meal eaten, and subjective responses to the meal was much weaker, and either statistically nonsignificant (P > 0.10) or only marginally so (0.10 > P > 0.05). For example, a large hot meal was chosen as readily for an "evening meal," and subjective responses to it were the same, at whatever circadian phase it was eaten. We conclude that food intake during forced desynchronization is dominated by the waking schedule rather than by circadian influences; some of the implications of these findings when eating habits and the metabolism of food are concerned, particularly in night workers, are considered briefly.     

Transient changes in the pattern of food intake following a simulated time-zone transition to the east across eight time zones

Twelve healthy adults were studied, singly or in groups of up to four, in an Isolation Unit before (control days) and for 3 days after a simulated time-zone transition to the east across 8 time zones (the clock being changed from 15:00 to 23:00 h). Subjects were free to choose how to pass their waking hours (though naps were forbidden), and to eat what and when they wanted. A wide selection of food was provided, though the subjects had to prepare it. Subjects completed food intake questionnaire on waking and at 3 h intervals during the waking day. This questionnaire assessed the reasons for choosing not to eat a meal or, if a meal was eaten, the reasons for doing so, the type of meal chosen and the reasons for this choice, and subjective responses to the meal (hunger before, enjoyment during, and satiety afterwards). Subjects also recorded the incidence and degree of indigestion and jet lag at 3 h intervals after the time-zone transition. Following the time-zone transition, the subjects experienced significant amounts of jet lag and recorded a significant increase in the incidence of indigestion. They also showed significant changes in their pattern of food intake, but, whereas the patterns of food intake were no longer significantly different from control days by the third post-shift day, the symptoms of jet lag and indigestion were still present then. The distribution of daytime meals was significantly affected on the first post-shift day, with a redistribution of the times that the main, hot meals were eaten; these times indicated some influence of an unadjusted body clock. On this day also, the reasons for determining food intake continued to be dominated by hunger and appetite (hunger even increasing in the frequency with which it was cited), and the reason for not eating a meal, by a lack of hunger. On both control and post-shift days, there was a marked effect of meal type upon the responses to food intake, with cold food being rated least and large hot meals most when appetite before the meal, enjoyment during it, and satiety afterward were considered. However, evidence suggested that the degree to which larger hot meals were preferred to cold meals was significantly less marked after the time-zone transition. On control days, sleep was unbroken; whereas, after the time-zone transition, all subjects woke on at least one of the 3 nights studied. During the first post-shift night, about half of the subjects ate a meal, the reason given being that they were “hungry.” On those occasions when subjects woke but did not eat a meal, the reason cited was because they “could not be bothered” as frequently as because they were “not hungry.”. A simulated time-zone transition is associated with significant changes to the incidence of indigestion, pattern of food intake, and subjective responses to food. However, these changes are generally transient and are only weakly linked to the sensation of jet lag.     

Lack of Evidence for a Marked Endogenous Component Determining Food Intake in Humans During Forced Desynchrony

In an attempt to investigate the relative importance of endogenous and exogenous factors in determining food intake, 14 healthy subjects were studied while living in an Isolation Unit (where external time cues were absent) for eighteen 28 h “days” (equal to 21 solar days). The subjects were free to spend their waking time as they chose, and they had a free choice of what they ate and when they ate it. The only restrictions were that no naps were allowed in the “daytime,” that some time was required to perform a variety of tests at regular intervals throughout the 18.67 h waking periods, and that any food preparation had to be performed by the subjects themselves. Core (rectal) temperature and activity were monitored throughout, and the subjects answered a questionnaire on their eating habits at 3 h intervals during the waking periods. The questionnaire investigated reasons for eating or not eating a meal during the previous 3 h and, if a meal had been eaten, its type, the factors influencing that choice, and the subjects’ subjective responses (hunger before, enjoyment during, and satiety after) to it. The results were analyzed (two-way ANOVA) in terms of both the imposed day length (the exogenous component) and the free-running period of the temperature rhythm (the endogenous component). Results indicated that by far the main reason for eating/not eating was hunger/lack of hunger rather than factors such as food availability and time-pressure. There were statistically significant effects of time within the imposed waking periods upon the type of meal eaten—“breakfast” tending to be a snack, “lunch” a small hot meal, and the “evening meal” a large hot meal. Hot meals (whether small or large) were associated with more hunger before the meal, more enjoyment of the meal, and a greater degree of satiety afterward than were cold meals. These effects suggest that the individuals adjusted their eating habits to fit in with the imposed wake times. By contrast, the effect of circadian phase upon food intake, the type of meal eaten, and subjective responses to the meal was much weaker, and either statistically nonsignificant (P > 0.10) or only marginally so (0.10 > P > 0.05). For example, a large hot meal was chosen as readily for an “evening meal,” and subjective responses to it were the same, at whatever circadian phase it was eaten. We conclude that food intake during forced desynchronization is dominated by the waking schedule rather than by circadian influences; some of the implications of these findings when eating habits and the metabolism of food are concerned, particularly in night workers, are considered briefly.     

Food intake in healthy young adults: effects of time pressure and social factors

Some factors influencing food intake and subjective responses to meals were assessed in 2 groups (n=40 and n=36) of healthy university students. Both groups were studied for 6 days and included both "structured" and "unstructured" times. A questionnaire was completed by all subjects at 3 h intervals while awake. The questionnaires asked the subjects to state the factors that led them to choose to eat or not to eat a meal in the previous 3 h. If they ate a meal, they were required to describe the type of meal eaten and their responses to it-their hunger before it, their enjoyment of the meal itself, and their degree of satisfaction afterwards. Subjects were also asked to describe the type of meal that they would like to have eaten (the desired meal) in the absence of any restraints due to time pressure, cost, and so on. In the first group, 3 "structured" (working) and 3 "unstructured" (rest) days were chosen. Consistant with our previous studies, structured days, as compared to unstructured days, were associated with smaller meals and less positive subjective responses to them. Also, the meals that were eaten were often smaller than those that were desired, or were even missed altogether, due to time pressure. Not only were the meals eaten on unstructured days larger and rated, to by the subjects more positively, but also there was an additional positive effect if the meal played a social role. In the second group, 6 days were chosen, during which there were structured and unstructured 3 h periods. Many of the findings (with regard to reasons for eating or not eating a meal, and the effect of meal size upon subjective responses to it, for example) were the same as in the first group. However, the effect of structured vs. unstructured 3 h periods was significantly less marked than the effect of structured vs. unstructured days that had been found in the first group, and effects due to social factors and time pressure were less reliably present. The results indicate that food intake is affected by whether the whole or only part of the day is "structured" or "unstructured." These findings might be relevant to some problems faced by the workforce, in general, and by night workers, in particular.     

A comparison of eating habits between retired or semi-retired aged subjects and younger subjects in full-time work

An analysis of eating habits in older retired subjects (“No Work group”) and younger subjects employed in full-time work (“Work group”) has been carried out. It used a questionnaire that assessed why individuals chose to eat or not to eat meals during the course of the day, and subjective responses to the meals. The questionnaire was answered every three hours over a “typical week” which, for the Work group, entailed working during the weekdays and resting at the weekend. For the “No Work” group, breakfast was the most frequently taken meal of the day whereas, for the “Work” group, this meal was often missed. Patterns of meal intake were not significantly different between the weekdays and weekend for the “No Work” group, but the “Work” group ate more hot food at the weekend. The reasons cited for eating/not eating a meal and for choosing the type of meal eaten were dominated by hunger/lack of hunger in both groups. In addition, whereas habits were also important for the “No Work” group, it was time availability or the lack of it that was of major importance to the Work group, though this was significantly less important at the weekend. Meals which required more time for preparation and cooking were appreciated significantly more (appetite before the meal, enjoyment during it, and satiety afterwards) than meals such as snacks and cold food, which could be prepared more quickly. Some implications of these results, with regard to regular meals acting as a social zeitgeber in older subjects and the additional constraints imposed upon night workers, are considered.     

Measurement of, and some reasons for, differences in eating habits between night and day workers

A questionnaire was designed to assess the following: why working people chose to eat or not to eat at a particular time of day; the factors that influenced the type of food eaten; and subjective responses to the meal (hunger before, enjoyment during, satiety afterward). Self-assessments were done every 3 h during a typical week containing work and rest days, by one group of 50 day workers and another group of 43 night workers. During the night work hours compared to rest days, night workers evidenced a significantly altered food intake, with a greater frequency of cold rather than hot food (p < 0.001). The type and frequency of meals were influenced significantly more (p < 0.05) by habit and time availability and less by appetite. This pattern continued into the hours immediately after the night shift had ended. In day workers food intake during work hours, compared to rest days, was also influenced significantly more often (p < 0.05) by time availability than hunger, but less so than with night workers. Moreover, day workers were less dependent than night workers upon snacks (p = 0.01), and any significant differences from rest days did not continue beyond work hours. Not only did night workers change their eating habits during work days more than did day workers but also they looked forward to their meals significantly less (p < 0.001) and felt more bloated after consuming them (p < 0.05), such effects being present to some extent during their rest days also. These findings have clear implications for measures designed to ease eating problems that are commonly problematic in night workers.     

Food Intake in Healthy Young Adults: Effects of Time Pressure and Social Factors

Some factors influencing food intake and subjective responses to meals were assessed in 2 groups (n=40 and n=36) of healthy university students. Both groups were studied for 6 days and included both “structured” and “unstructured” times. A questionnaire was completed by all subjects at 3 h intervals while awake. The questionnaires asked the subjects to state the factors that led them to choose to eat or not to eat a meal in the previous 3 h. If they ate a meal, they were required to describe the type of meal eaten and their responses to it—their hunger before it, their enjoyment of the meal itself, and their degree of satisfaction afterwards. Subjects were also asked to describe the type of meal that they would like to have eaten (the desired meal) in the absence of any restraints due to time pressure, cost, and so on. In the first group, 3 “structured” (working) and 3 “unstructured” (rest) days were chosen. Consistant with our previous studies, structured days, as compared to unstructured days, were associated with smaller meals and less positive subjective responses to them. Also, the meals that were eaten were often smaller than those that were desired, or were even missed altogether, due to time pressure. Not only were the meals eaten on unstructured days larger and rated, to by the subjects more positively, but also there was an additional positive effect if the meal played a social role. In the second group, 6 days were chosen, during which there were structured and unstructured 3 h periods. Many of the findings (with regard to reasons for eating or not eating a meal, and the effect of meal size upon subjective responses to it, for example) were the same as in the first group. However, the effect of structured vs. unstructured 3 h periods was significantly less marked than the effect of structured vs. unstructured days that had been found in the first group, and effects due to social factors and time pressure were less reliably present. The results indicate that food intake is affected by whether the whole or only part of the day is “structured” or “unstructured.” These findings might be relevant to some problems faced by the workforce, in general, and by night workers, in particular.     

Measurement of,and Some Reasons for,Differences in Eating Habits Between Night and Day Workers

A questionnaire was designed to assess the following: why working people chose to eat or not to eat at a particular time of day; the factors that influenced the type of food eaten; and subjective responses to the meal (hunger before, enjoyment during, satiety afterward). Self-assessments were done every 3h during a typical week containing work and rest days, by one group of 50 day workers and another group of 43 night workers. During the night work hours compared to rest days, night workers evidenced a significantly altered food intake, with a greater frequency of cold rather than hot food (p < 0.001). The type and frequency of meals were influenced significantly more (p < 0.05) by habit and time availability and less by appetite. This pattern continued into the hours immediately after the night shift had ended. In day workers food intake during work hours, compared to rest days, was also influenced significantly more often (p < 0.05) by time availability than hunger, but less so than with night workers. Moreover, day workers were less dependent than night workers upon snacks (p = 0.01), and any significant differences from rest days did not continue beyond work hours. Not only did night workers change their eating habits during work days more than did day workers but also they looked forward to their meals significantly less (p < 0.001) and felt more bloated after consuming them (p < 0.05), such effects being present to some extent during their rest days also. These findings have clear implications for measures designed to ease eating problems that are commonly problematic in night workers.     

Behavioural contributions to the regulated intake of plant secondary metabolites in koalas

In a given period of time, herbivores often eat less as dietary plant secondary metabolite (PSM) concentrations increase. This reduction in total food intake is interpreted as a need for the herbivore to regulate PSM ingestion in order to avoid toxication. However, regulation of PSM ingestion involves more than the reduction of total intake; it involves an alteration of meal patterns, through a reduction in the number and/or the size of the meals eaten. Despite this, studies of how herbivores alter their meal patterns when offered varying concentrations of PSMs are rare. We investigated whether koalas adjust the number and/or the size of their meals when offered eucalypt foliage varying naturally in concentrations of formylated phloroglucinol compounds (FPCs), a group of PSMs that have previously been shown to inhibit total food intake. High FPC concentrations caused koalas to eat more slowly, eat shorter meals and eat less per meal, which resulted in a reduced total intake. Because increasing FPC concentrations did not cause koalas to alter the number of meals that they ate, clear individual differences between koalas were observed, where some consistently ate fewer larger meals and others ate many smaller meals. Thus, different feeding strategies may still achieve the same outcome of a regulated intake of PSMs. The changes observed match the meal patterns of other herbivores ingesting PSMs known to stimulate nausea and emetic pathways, supporting the idea that feedback signals from nausea are an important way that koalas avoid toxication when eating eucalypt foliage.     

Appetite at "high altitude" [Operation Everest III (Comex-'97)]: a simulated ascent of Mount Everest.

We hypothesized that progressive loss of body mass during high-altitude sojourns is largely caused by decreased food intake, possibly due to hypobaric hypoxia. Therefore we assessed the effect of long-term hypobaric hypoxia per se on appetite in eight men who were exposed to a 31-day simulated stay at several altitudes up to the peak of Mt. Everest (8,848 m). Palatable food was provided ad libitum, and stresses such as cold exposure and exercise were avoided. At each altitude, body mass, energy, and macronutrient intake were measured; attitude toward eating and appetite profiles during and between meals were assessed by using questionnaires. Body mass reduction of an average of 5 +/- 2 kg was mainly due to a reduction in energy intake of 4.2 +/- 2 MJ/day (P < 0.01). At 5,000- and 6,000-m altitudes, subjects had hardly any acute mountain sickness symptoms and meal size reductions (P < 0.01) were related to a more rapid increase in satiety (P < 0.01). Meal frequency was increased from 4 +/- 1 to 7 +/- 1 eating occasions per day (P < 0. 01). At 7,000 m, when acute mountain sickness symptoms were present, uncoupling between hunger and desire to eat occurred and prevented a food intake necessary to meet energy balance requirements. On recovery, body mass was restored up to 63% after 4 days; this suggests physiological fluid retention with the return to sea level. We conclude that exposure to hypobaric hypoxia per se appears to be associated with a change in the attitude toward eating and with a decreased appetite and food intake.     

Independent and combined effects of eating rate and energy density on energy intake,appetite, and gut hormones

Objective:

Energy density (ED) and eating rate (ER) influence energy intake; their combined effects on intake and on postprandial pancreatic and gut hormone responses are undetermined. To determine the combined effects of ED and ER manipulation on voluntary food intake, subjective appetite, and postprandial pancreatic and gut hormone responses.

Design and Methods:

Twenty nonobese volunteers each consumed high (1.6 kcal g^?1; HED) and low (1.2 kcal g^?1; LED) ED breakfasts slowly (20 g min^?1; SR) and quickly (80 g min^?1; FR) ad libitum to satiation. Appetite, and pancreatic and gut hormone concentrations were measured periodically over 3 h. Ad libitum energy intake during the subsequent lunch was then measured.

Results:

Main effects of ED and ER on energy intake and a main effect of ER, but not ED, on mass of food consumed were observed, FR and HED being associated with increased intake (P < 0.05). Across all conditions, energy intake was highest during FR‐HED (P ≤ 0.01). Area under the curve (AUC) of appetite ratings was not different between meals. Main effects of ED and ER on insulin, peptide‐YY, and glucagon‐like peptide‐1 AUC (P < 0.05) were observed, FR and HED being associated with larger AUC. No effects on active or total ghrelin AUC were documented. Total energy intake over both meals was highest during the FR‐HED trial with the greatest difference between FR‐HED and SR‐LED trials (P ≤ 0.01).

Conclusion:

Consuming an energy dense meal quickly compounds independent effects of ER and ED on energy intake. Energy compensation at the following meal may not occur despite altered gut hormone responses.

     

Continuous infusion of cholecystokinin and meal pattern in the rat

Purified natural cholecystokinin (CCK-33) was infused continuously for two days at a rate of 5.9 μg/hr in two rats trained to bar-press for food (Noyes pellet 45 mg) on a fixed ratio of five bar presses to obtain one pellet. The animals also received control surgery and were tested in the operant chamber for two days, one prior to and the other following the CCK-33 treatment. CCK-33 suppressed the number of meals, the total amount of food eaten, and the total duration of time spent eating. However, the size of each meal and the rate of intake were not affected. The CCK effect did not interact with the light-dark phases of diurnal cycle. It appears that a major effect of continuous systemic elevation of CCK-33 is to reduce food intake by prolonging the satiety period rather than by decreasing the individual meal size.     

Mechanisms regulating salt intake in fifth-instar nymphs of Locusta migratoria

Abstract. Investigations were undertaken into the mechanisms controlling regulation of salt intake in fifth-instar nymphs of Locusta migratoria L. Initially, the pattern of feeding was recorded for 24 h in locusts fed a chemically-defined food either with or without salt. Differences were apparent from the first meal, with smaller meals being eaten more frequently on the salt-free food over the next 8h. As a result, total food intake over the first 8h was similar on the two foods. By 24 h, however, intake of the salt-free food was considerably reduced and the rate of prefeeding rejections was high. Next, following a period of pretreatment (24 or 48 h) on one of these two foods, responses were recorded to glass-fibre discs impregnated with salts, artificial foods differing in salt content, and wheat germ. Haemolymph amino acid titres were also recorded in locusts feeding ad libitum on salt-free or salt-containing food to test the 'metabolic bottleneck' hypothesis for explaining rejection of a salt-free food after a period of feeding on it. Finally, the role of learning was investigated in experiments in which distinctive plant odours and flavours were paired with foods lacking or containing salt. Results across all the experiments indicate that regulation of mineral intake in locust nymphs involves a number of mechanisms, including modulation of locomotory behaviour, innate taste responses and learning. Additionally, there was evidence of a sex difference in salt appetite.     

Nonlinear time series analysis of food intake in the dab and the rainbow trout

Evidence suggests that dab and rainbow trout are able to quickly adjust their food intake to an appropriate level when offered novel diets. In addition day-to-day and meal-to-meal food intake varies greatly and meal timing is plastic. Why this is the case is not clear: Food intake in fish is influenced by many factors, however the hierarchy and mechanisms by which these interact is not yet fully understood. A model of food intake may be helpful to understand these phenomena; to determine model type it is necessary to understand the qualitative nature of food intake. Food intake can be regarded as an autoregressive (AR) time series, as the amount of food eaten at time t will be influenced by previous meals, and this allows food intake to be considered using time series analyses. Here, time series data were analysed using nonlinear techniques to obtain qualitative information from which evidence for the hierarchy of mechanisms controlling food intake may be drawn. Time series were obtained for a group of dab and individuals and a group of rainbow trout for analysis. Surrogate data sets were generated to test several null hypotheses describing linear processes and all proved significantly different to the real data, suggesting nonlinear dynamics. Examination of topography and recurrence diagrams suggested that all series were deterministic and non-stationary. The point correlation dimension (PD2i) suggested low-dimensional dynamics. Our findings suggest therefore that any model of appetite should create output that is deterministic, non-stationary, low-dimensional and having nonlinear dynamics.     

Development of an artificial diet for the western corn rootworm

Toxicants may cause insects to avoid a bait, and yet bait efficacy is dependent upon insects ingesting it in adequate quantities. Amounts ingested are, in turn, determined by meal frequency, meal durations and ingestion rate within meals, but to date no report has been made of these variables for domestic cockroaches. We report an experiment in which sixth instar German cockroach, Blattella germanica, nymphs were initially able to self-select their protein and carbohydrate intake independently, then daily at the start of the scotophase some insects had their choice of foods replaced by a single treatment food, which varied through the presence or absence of protein, carbohydrate, and insecticide. Insect behaviour was recorded for the following 5 h, and the data were subsequently subjected to bout analysis in order to identify discrete meals. The age of insects in days on first exposure to a treatment food (`age') and the amount of food eaten in the observation period were both recorded and included in the analysis. Amounts eaten were affected by insect age and food nutrient content, but not by the presence of insecticide. Toxicant effects were, however, seen on average meal duration and meal frequency, in interactions with age and food nutrient effects. These results suggest ways in which direct observations of behaviours may lead to improved bait design.     

Effect of Alginate on Satiation,Appetite, Gastric Function,and Selected Gut Satiety Hormones in Overweight and Obesity

Lack of control of food intake, excess size, and frequency of meals are critical to the development of obesity. The stomach signals satiation postprandially and may play an important role in control of calorie intake. Sodium alginate (based on brown seaweed Laminaria digitata) is currently marketed as a weight loss supplement, but its effects on gastric motor functions and satiation are unknown. We evaluated effects of 10 days treatment with alginate or placebo on gastric functions, satiation, appetite, and gut hormones associated with satiety in overweight or obese adults. We conducted a randomized, 1:1, placebo‐controlled, allocation‐concealed study in 48 overweight or obese participants with excluded psychiatric comorbidity and binge eating disorder. All underwent measurements of gastric emptying (GE), fasting, and postprandial gastric volumes (GVs), postprandial satiation, calorie intake at a free choice meal and selected gut hormones after 1 week of alginate (three capsules vs. matching placebo per day, ingested 30 min before the main meal). Six capsules were ingested with water 30 min before the GE, GV, and satiation tests on days 8–10. There were no treatment group effects on GE or volumes, gut hormones (ghrelin, cholecystokinin (CCK), glucagon‐like peptide‐1 (GLP‐1), peptide YY (PYY)), satiation, total and macronutrient calorie intake at a free choice meal. There was no difference detected in results between obese and overweight patients. Alginate treatment for a period of 10 days showed no effect on gastric motor functions, satiation, appetite, or gut hormones. These results question the use of short‐term alginate treatment for weight loss.     

Effect of meal type on specific dynamic action in the green shore crab,Carcinus maenas

The effect of meal type on specific dynamic action was investigated in the green shore crab, Carcinus maenas. When the crabs were offered a meal of fish, shrimp, or mussel of 3 % of their body mass the duration of the SDA response and thus the resultant SDA was lower for the mussel, compared with the shrimp or fish meals. In feeding behaviour experiments the crabs consumed almost twice as much mussel compared with fish or shrimp. When the animals were allowed to feed on each meal until satiated, the differences in the SDA response were abolished. The mussel was much softer (compression test) than the fish or shrimp meal, and meal texture is known to affect the SDA response in amphibians and reptiles. When the crabs were offered a meal of homogenized fish muscle or whole fish muscle, the SDA for the homogenized meal was approximately 35 % lower. This suggested that a significant portion of the SDA budget in decapod crustaceans may be related to mechanical digestion. This is not unexpected since the foregut is supplied by over forty muscles which control the cutting and grinding movements of the gastric mill apparatus. There were slight, but significant differences in protein, lipid, moisture and total energy content of each meal type. Three prepared meals that were high in either protein, lipid or carbohydrate were offered to the crabs to determine if the nutrient content was also a contributing factor to the observed differences in the SDA. The crabs did not eat the prepared meals as readily as the natural food items and as they are messy feeders there was a large variation in the amount of food eaten. The lack of significant differences in the SDA response as a function of nutrient content was likely due to differences in amount of food eaten, which is a major factor determining the SDA response. The differences in SDA when consuming natural food items were likely due to a combination of the costs of mechanical digestion, variation in nutrient content and food preference: determining how each of these factors contributes to the overall SDA budget remains a pressing question for comparative physiologists.     

The pattern of feeding of first instar nymphs of Schistocerca americana

ABSTRACT The feeding behaviour of nymphs Schistocerca americana (Drury) was recorded throughout the light phases of the first stadium using a behavioural event recording program on a microcomputer. Most food was ingested on day 4 of the stadium, very little on day 1 and none on day 6, the final day of the stadium. Only 26–45% of the total food intake over the stadium occurred during the dark periods and more food was eaten in the last 4 h of each light period than earlier. Feeding occupied only about 5% of the total time. Variation in food intake was a consequence primarily of changes in the numbers of meals. After day 1, the average meal size did not change significantly. Meal length increased relatively slightly compared with meal size as a consequence of an increase in the proportion of time spent feeding in each meal as meal size increased. Meal size was correlated with the length of the previous interfeed suggesting a volumetric regulation. The distribution of pauses within meals was also consistent with the thesis that meal size is governed by the level of excitation in the central nervous system at the start of the meal.     

Patterns in food intake correlate with body mass index

Quantifying eating behavior may give clues to both the physiological and behavioral mechanisms behind weight regulation. We analyzed year-long dietary records of 29 stable-weight subjects. The records showed wide daily variations of food intake. We computed the temporal autocorrelation and skewness of food intake mass, energy, carbohydrate, fat, and protein. We also computed the cross-correlation coefficient between intake mass and intake energy. The mass of the food intake exhibited long-term trends that were positively skewed, with wide variability among individuals. The average duration of the trends (P = 0.003) and the skewness (P = 0.006) of the food intake mass were significantly correlated with mean body mass index (BMI). We also found that the lower the correlation coefficient between the energy content and the mass of food intake, the higher the BMI. Our results imply that humans in neutral energy balance eating ad libitum exhibit a long-term positive bias in the food intake that operates partially through the mass of food eaten to defend against eating too little more vigorously than eating too much.