Food Intake In Human Subjects Research Articles

Effect of an Acute Insect Preload vs. an Almond Preload on Energy Intake, Subjective Food Consumption and Intestinal Health in Healthy Young Adults.

Protein is considered the most satiating macronutrient, and its effect on satiety and food intake is source-dependent. For the first time, we compared the effect of the administration of an insect or almond preload, both containing 20 g of protein, on appetite and food intake in human subjects. Participants consumed both foods and a vehicle as a liquid preload on three separate days. They were then offered a breakfast and lunch buffet meal at which food intake was measured. Visual analogue scale (VAS) questionnaires were completed following the three preloads to assess appetite and other sensations. At breakfast, reduced energy intake was observed for both preloads compared with vehicle. At lunch, food intake only differed in the insect group, which consumed more than the vehicle. Insect preload increased the total amount of protein ingested with a slight increase in total energy consumed, differently than almond, which significantly increased total protein and energy consumed. There was no correlation between indigestion-sensation ratings and food intake. Moreover, the insect preload resulted in lower sleepiness and tiredness ratings compared with the almond preload. Thus, insect-derived protein may be suitable as a safe ingredient for snacks intended for elderly or infirm patients who require increased protein intake.

Afferent signals regulating food intake.

Food intake is a regulated system. Afferent signals provide information to the central nervous system, which is the centre for the control of satiety or food seeking. Such signals can begin even before food is ingested through visual, auditory and olfactory stimuli. One of the recent interesting findings is the demonstration that there are selective fatty acid taste receptors on the tongue of rodents. The suppression of food intake by essential fatty acids infused into the stomach and the suppression of electrical signals in taste buds reflect activation of a K rectifier channel (K 1.5). In animals that become fat eating a high-fat diet the suppression of this current by linoleic acid is less than that in animals that are resistant to obesity induced by dietary fat. Inhibition of fatty acid oxidation with either mercaptoacetate (which blocks acetyl-CoA dehydrogenase) or methylpalmoxirate will increase food intake. When animals have a choice of food, mercaptoacetate stimulates the intake of protein and carbohydrate, but not fat. Afferent gut signals also signal satiety. The first of these gut signals to be identified was cholecystokinin (CCK). When CCK acts on CCK-A receptors in the gastrointestinal tract, food intake is suppressed. These signals are transmitted by the vagus nerve to the nucleus tractus solitarius and thence to higher centres including the lateral parabrachial nucleus, amygdala, and other sites. Rats that lack the CCK-A receptor become obese, but transgenic mice lacking CCK-A receptors do not become obese. CCK inhibits food intake in human subjects. Enterostatin, the pentapeptide produced when pancreatic colipase is cleaved in the gut, has been shown to reduce food intake. This peptide differs in its action from CCK by selectively reducing fat intake. Enterostatin reduces hunger ratings in human subjects. Bombesin and its human analogue, gastrin inhibitory peptide (also gastrin-insulin peptide), reduce food intake in obese and lean subjects. Animals lacking bombesin-3 receptor become obese, suggesting that this peptide may also be important. Circulating glucose concentrations show a dip before the onset of most meals in human subjects and rodents. When the glucose dip is prevented, the next meal is delayed. The dip in glucose is preceded by a rise in insulin, and stimulating insulin release will decrease circulating glucose and lead to food intake. Pyruvate and lactate inhibit food intake differently in animals that become obese compared with lean animals. Leptin released from fat cells is an important peripheral signal from fat stores which modulates food intake. Leptin deficiency or leptin receptor defects produce massive obesity. This peptide signals a variety of central mechanisms by acting on receptors in the arcuate nucleus and hypothalamus. Pancreatic hormones including glucagon, amylin and pancreatic polypeptide reduce food intake. Four pituitary peptides also modify food intake. Vasopressin decreases feeding. In contrast, injections of desacetyl melanocyte-stimulating hormone, growth hormone and prolactin are associated with increased food intake. Finally, there are a group of miscellaneous peptides that modulate feeding. beta-Casomorphin, a heptapeptide produced during the hydrolysis of casein, stimulates food intake in experimental animals. In contrast, the other peptides in this group, including calcitonin, apolipoprotein A-IV, the cyclized form of histidyl-proline, several cytokines and thyrotropin-releasing hormone, all decrease food intake. Many of these peptides act on gastrointestinal or hepatic receptors that relay messages to the brain via the afferent vagus nerve. As a group they provide a number of leads for potential drug development.

The acute effect of D-tagatose on food intake in human subjects

A double-blind randomized crossover study was performed with nineteen normal-weight men to investigate the effect on subsequent ad libitum food intake of replacing 29 g sucrose with 29 g D-tagatose as sweetener to a breakfast meal. D-Tagatose is a malabsorbed stereoisomer of fructose with potential application as a bulk sweetener. Food intake was measured at lunch offered 4 h after the breakfast meal, during the afternoon with access to abundant snacks, and finally at a supper buffet 9 h after the breakfast. Energy intake at lunch and during the snacking period was similar after ingesting the two sugars, while it was 15% lower after ingesting D-tagatose than with sucrose at supper (P < 0.05). Gastrointestinal factors such as the osmotic effects of unabsorbed D-tagatose causing distension of the gut might have mediated the acute appetite-suppressing effect. The present paper also refers to data from a preceding study in which we observed an increased self-reported energy intake after ingestion of D-tagatose compared with sucrose which, in fact, suggests a relative hyperphagic effect of D-tagatose. However, self-reported food intake may be biased by selective under-reporting and this subsequent study with a more controlled assessment of food intake was therefore conducted. This present study did not support any hyperphagic effect of D-tagatose, but rather suggests that D-tagatose may contribute to a reduced energy intake.

Effect of gastric distension on food intake and satiety in healthy human subjects

Background: Regulation of food intake is a complex process involving multiple signals. The interaction effect on food intake resulting from gastric signals and the amount of food previously eaten (e.g., a preload) has only insuffciently been explored. It is uncertain to give an example to which extent the volume and the composition of a meal affects food intake and satiety. The aim of the study was to investigate the effect of different volumes of two different macronutrient preloads on satiety and food intake in human subjects. Methods: 15 healthy male volunteers were studied in a randomized, 5-period crossover design. On each study day, subjects were asked to drink one of the following preloads: a) 400 m1 water (W); b) 400 ml carbohydrate (CH); c) 800 ml CH; d) 400 m1 protein (PRO) and e) 800 m1 PRO. 20 min later a standard test meal was presented on each occasion and subjects were free to eat and drink ad libitum. Volunteers scored feelings for hunger and fullness on a standard visual analogue scale throughout the experiments. The amount of food eaten, of fluid drunk as well as the eating time were assessed. Data were analysed using ANOVA. Results (see table): (Mean::': SEM). 800 m1 protein preload significantly increased feelings of fullness and reduced feelings of hunger (pS O.OOO5). Summary: I) Preloads of 800 ml significantly induced satiation and reduced food and calorie intake. 2) The effect was more pronounced after ingestion of the protein preload. Conclusion: Gastric distension induced by a preload I)induced early satiety and 2) reduced calorie intake. The effect was more pronounced with protein than with carbohydrate most likely reflecting differences in gastric emptying rates. 4971

Effects of extreme environments on food intake in human subjects.

Effects of extreme environments on food intake in human subjects are analysed as behavioural and physiological adaptations to annual and circadian rhythms, temperature and altitude. Effects of the environment on food intake through food availability have direct consequences on energy balance and body weight. Different geographical regions show variations in the composition of dietary foods, i.e. the relative proportions of carbohydrate, protein and fat. In developing countries the annual cycle appears to affect body weight through dependence on food availability. In West-European countries this effect appears to depend on physical activity. Energy and macronutrient intakes appear to follow a circadian pattern, with breakfast being relatively high in carbohydrate and dinner being relatively high in fat. In cold conditions, maintaining an adequate food intake is important in sustaining normal physiological responses to cold. Evidence for a possible cold-induced increase in appetite is poor. A condition influencing level of intake is the palatability of the food. High altitude, i.e. hypobaric hypoxia, appears to reduce appetite, energy intake and body mass, irrespective of acute mountain sickness (AMS). Meal size is reduced and meal frequency increased. Under circumstances of AMS, dissociation between appetite and hunger occurs. Thus, spontaneous adaptation to extreme environments requiring increased energy intake occurs first by adaptation of body weight to a new energy balance. In general, prevention of a negative energy balance occurs by learning with respect to food intake. After return to normal, adjustment of energy intake to the original energy balance occurs with restoration of body weight.

Reanalysis of the effects of phenylalanine, alanine, and aspartame on food intake in human subjects

In 1987 Ryan-Harshman et al. reported finding no effects on food intake after administering high doses (up to 10.08 g) of phenylalanine and aspartame in capsules to human volunteers. However, this is contrary to the results of other studies, and trends in their tabulated data suggest that certain effects may have been overlooked. This is confirmed by a reanalysis of the raw data (available from a Ph.D. thesis: Ryan-Harshman, 1987) that can be interpreted as showing a dose-related suppression of food intake by phenylalanine. Furthermore, the data are consistent with an anorexic action of aspartame and perhaps also of alanine (which was designated as the placebo treatment by Ryan-Harshman et al.). These, together with other findings, suggest that the appetite effects of amino acids and small peptides should be investigated further. In addition to its theoretical importance, such work may have potential for therapeutic applications.

Umami and appetite: Effects of monosodium glutamate on hunger and food intake in human subjects

Subjects consumed soup (beef consomme) preloads of a fixed size containing different concentrations of monosodium L-glutamate (MSG). Effects on appetite following these preloads, and when no soup was consumed, were assessed in 3 studies. The soups supplemented with MSG were rated as more “pleasant,” more “savoury” and more “satisfying” than soup with no added MSG. Compared with the no preload condition, consumption of the soups initially reduced appetitive motivational ratings and increased fullness ratings, but did not alter food intake in a test meal begun either 2 or 30 minutes later. This immediate inhibition of subjective motivation to eat was unaffected by MSG concentration. The failure of the soups to reduce subsequent food intake is presumably due to their low energy content (<10 kcal) and indicates that sensory stimulation alone is insufficient to reduce appetite. Indeed, the most important finding concerning MSG showed that motivation to eat recovered more rapidly following a lunchtime meal in which MSG-supplemented soup was served as the first course (compared both with the effect of unsupplemented soup and no preload). It is suggested tentatively that MSG through its stimulation of orosensory receptors and/or by improving the palatability of the soup may have influenced the metabolic disposal of nutrients consumed in the previous meal.

Uncoupling Sweet Taste and Calories Effects of Saccharin on Hunger and Food Intake in Human Subjects

Uncoupling Sweet Taste and Calories Effects of Saccharin on Hunger and Food Intake in Human Subjects

Separating the actions of sweetness and calories: Effects of saccharin and carbohydrates on hunger and food intake in human subjects

A comparison was made of the effects on hunger and food intake of consuming preloads varying in sweetness and energy content. The preloads were a plain (unsweetened) yogurt, and the same yogurt sweetened to equal intensity with saccharin or glucose, or supplemented with starch. This balanced design made it possible to assess the consequences of adding sweetness to food as well as the consequences of substituting a nonnutritive sweetener for a caloric sweetener. Subjects (N=24, repeated measures design) ate the preload at midday and returned one hour later for a sandwich lunch. Food intake in this meal was measured directly, and intake during the remaining part of the day was monitored using home recording in diaries. Hunger was assessed using subjective ratings of motivation to eat. Food intake at lunchtime was significantly greater following the saccharin compared with the plain preload, and parallel effects were revealed by the motivational ratings. Saccharin also stimulated further increases in intake after lunch. Food intake was lowest following the high-energy preloads, with the starch supplemented yogurt producing somewhat the largest suppression of intake. The results confirm and extend previous findings showing that intense sweeteners do not possess the same satiating capacity as glucose and sucrose. The stimulation of appetite by saccharin may be due to its sweet taste and also to effects on postingestive mechanisms.

Differential effect of d-fenfluramine and metergoline on food intake in human subjects

This study investigated the effect of the 5-HT receptor blocker metergoline (MTG) on d-fenfluramine (d-FF)-induced reduction of food intake in 13 normal male human volunteer subjects. Food was freely available for 2h, 4h after drug administration, from a four-channel automated food dispenser. d-FF (30 mg) reduced total food intake and exerted a marked effect on non-sweet food which was attenuated by the addition of MTG (4 mg). d-FF had less effect on sweet-tasting food while intake of sweet food was significantly increased by MTG. There was a significant interaction between d-FF and MTG on sweet-tasting foods. No effect on MTG was observed on d-FF-induced changes in ratings of hunger.

The Effect of the 5‐HT Releasing Drug d‐Fenfluramine and the 5‐HT Receptor Blocker, Metergoline, on Food Intake in Human Subjects

The Effect of the 5‐HT Releasing Drug <i>d</i>‐Fenfluramine and the 5‐HT Receptor Blocker, Metergoline, on Food Intake in Human Subjects

Effect of exercise on food intake in human subjects

We review human studies of the effect of physical activity on food intake. Most are flawed by inaccurate measurement of energy expenditure and/or energy intake, by lack of controls, or by short study periods. While lean persons seem to regulate and maintain weight well, studies in obese subjects are inconclusive. At realistic exercise intensities, the effect on weight is generally small. There is little evidence of inhibition of food intake. In our metabolic ward studies, treadmill exercise neither enhanced nor inhibited food intake in obese individuals. Since intake remained fixed, a negative energy balance was observed with exercise. When more savory food was provided, intake again remained fixed as exercise was increased, but subjects ate more throughout and maintained positive energy balance. Thus, energy output does not regulate energy intake closely in the obese. Food-related cues seem more important than exercise-generated signals. The beneficial effect of exercise on body weight is limited to the extra calories expended. Further careful studies are essential to differentiate effects of kinds and intensities of exercise.

Reflex insulin response associated to food intake in human subjects

The occurrence of a reflex insulin discharge at the beginning of a meal, and its possible influence on intake were studied in 7 normal weight humans. Each subject was tested twice under three standard meal conditions. The evolutions of insulinemia and glycemia were recorded over an 84 min observation period, starting 2 min before food presentation. Blood was drawn continuously from an antecubital vein, and collected in 1-min samples for the first 30 min, and then in 3-min samples. The average glycemia curve was stable until some 18–20 min after meal onset. By contrast, a significant rise in plasma insulin appeared as early as the 4th min after meal onset and it is hypothesized to be preabsorptive, of cephalic and/or gastric origin. However, inter-test variations were large even in the same person. Schematically, three types of early insulin responses were observed: high and/or sustained rise, moderate and/or short increase, moderate decrease in plasma insulin. The shape of the early insulin response was not related to any meal characteristic. The potential biological and behavioral significance of the early insulin release is discussed.

How flavour and appearance affect human feeding

It is the purpose of this paper to consider the ways in which the different sensory aspects of food presentation such as flavour, appearance, portion size and shape influence food intake in human subjects within the range of normal body-weights. One way in which the sensory properties of food influence feeding is by contributing to a form of satiety which is partly specific for the particular food eaten.

Psychopharmacology of anorectic drugs in man

1. 1. In recent years we have been engaged in a series of studies designed to investigate whether observations made on the actions of anorectic drugs in experimental animals have their parallels in man. 2. 2. Using techniques to quantify changes in hunger and food intake in human subjects we have shown that the centrally-acting anorectic drugs d-amphetamine (d-Amp) and fenfluramine (FF) reduce visual analogue scale (VAS) ratings of hunger in a dose-related manner. Furthermore, the effects of such drugs on hunger closely correspond to their effects on food intake. 3. 3. With regard to possible underlying neurochemical mechanisms we have examined the effect of pimozide (PMZ), a relatively specific dopamine (DA) receptor blocking compound, on d-Amp-induced anorexia and arousal. 2 mg PMZ caused no reduction of the anorexia induced by 10 mg d-Amp whereas it did attenuate its stimulant action. Thus DA mechanisms may be less important in d-Amp anorexia than in d-Amp arousal, a view which is consistent with some animal data.