David A. Booth

Food‐conditioned Eating Preferences and Aversions with Interoceptive Elements: Conditioned Appetites and Satieties

The adaptive importance of acquired feeding habits has long been acknowledged in research on obesity1 and animal foraging2 for example. Yet so few experiments have measured learning under physiologically and ecologically normal conditions that there is insufficient information for effective applications in the clinic and everyday life,3 the foods4 or Pharmaceuticals5 industries, or animal husbandry.6

Starch content of ordinary foods associatively conditions human appetite and satiation, indexed by intake and eating pleasantness of starch paired flavours

After one experience with the effects of a disguised augmentation of the starch content of a food eaten early in a meal, there was a decrease in the amount of that food eaten subsequently at meals on a menu that included the same flavours. Starch eaten late in the meal did not establish this suppression of intake of the item having a flavour paired with the extra starch, but did strengthen its subjective satiating effects, i.e., increased the reduction in rated pleasantness that occurs on eating most foods. When taken as snacks, the same starch-augmented foods had a direct satiating effect, similar in size to the satiating effect of believing the food to be high in calories: 20 min after ingesting the starch, both the amounts the consumer wished to eat and the ratings for pleasantness of foods on a separate menu were reliably lower than after the control snack. Associative conditioning of the pleasantness of eating the flavours of snacks augmented with starch also occurred, resulting in a pattern of acquired responses that accounted for the previously observed differentiation of meal sizes: that is, a conditioned decrease in the pleasantness of a starch-associated flavour was observed when that flavour was eaten and tested in relatively replete states, and a conditioned increase in its pleasantness was observed when training and testing were carried out during normal hunger. Thus, at least parts of both the appetite for a food and the satisfaction from it can be learned from experience of the after-effects of the food’s starch contents.

Localization of the Adrenergic Feeding System in the Rat Diencephalon

Injection of 6 micrograms of aqueous norepinephrine elicits eating only when it takes place at sites within a limited region of the rat brain. The distribution of effective sites coincides with that of systems connected to an extrahypothalamic pathway between the limbic forebrain and tegmental motor systems. It does not correspond to those parts of the lateral hypothalamus thought to control normal feeding.

Hunger elicited in the rat by a single injection of bovine crystalline insulin

Abstract Feeding and drinking responses to varying subcutaneous doses of short-acting insulin were determined. At a near optimum dose (20 units/kg), augmentation of feeding lasted 3–4 hr. The effect of repeated injections varied with the interval between them: less feeding was elicited by a second injection up to 3 days after the first. A single insulin injection augmented intakes of water, chow pellets, glucose solutions and sweetened or unsweetened milk concentrates. No differences were found between the effects of food deprivation and of injected insulin on intakes of glucose solutions flavoured with saccharine or quinine, even though increases in saccharine-flavoured glucose intake from first to second acquaintance were detectable. Thus, although repeated injection of long-acting insulin elicits sugar appetite, there was no evidence of immediate elicitation of an appetite for sweetened materials. It is postulated that in the rat, as in man, a single insulin injection causes physiological changes which paradoxically elicit a behavioral state similar to that elicited by food deprivation. Insulin augmented the rate of instrumental responding for food in both the fed and the starved rat.

Postabsorptively induced suppression of appetite and the energostatic control of feeding

The inhibition of feeding that follows intragastric administration of glucose had previously been shown to result in an ultimate net decrement in food intake which was equivalent in available energy to the amount of glucose loaded. Stomach loads of acetate, alanine, citrate, ethanol, glucose, glutamate, glycerol, lactate, oleate or valine (10 mmoles of each) were given in the present experiments. Food was withheld for 1 or 2 hr after gavage and then continuous access was restored. Relative to sodium chloride or urea loads, the metabolizable loads all inhibited feeding at some time in the subsequent few hr—in some cases at a time which followed complete absorption of the load. The net food intake decrement over 24 or 48 hr following gavage reliably correlated with the expected energy yield of the load. It is suggested that the primary metabolic control of food intake is an adjustment of the meal pattern which brings the current energy balance towards the null point.

Relative effectiveness of protein in the late stages of appetite suppression in man

Human subjects took a protein-rich or a protein-poor lunch and 2–3 hr later a supplementary meal of average protein content. Total caloric intake for the two meals was lower when the main meal contained a high proportion of protein. Therefore, calorie for calorie, amino acids contribute more than carbohydrates and fats to the suppression of hunger in the post-absorptive period.

Gastrointestinal factors in the acquisition of oral sensory control of satiation

Rats were given a series of starch meals. Half the meals were of a 65% starch solution with one taste added and the other meals were 5% carbohydrate which had been given another taste. After a few meals of each type, the dilute starch began to be taken in larger volumes. The rats were then given test meals of 35% starch having either flavour. The rate of intake towards the end of a meal decelerated more slowly in the presence of the taste given to dilute starch than in the presence of the flavour given to concentrated starch. The taste of dilute starch was not systematically preferred in a two-stimulus test. Thus there was a conditioned differentiation of the oral control of satiation: the onset of satiety was slowed in the presence of oral cues which had been associated with the passage of very little carbohydrate. The oral control of satiety was acquired even when meals differed in starch concentration during their first 5 min only. In contrast, concentration differences after the first 5 min did not generate an adequate unconditioned stimulus. It appeared therefore that the unconditioned stimulus was related to the phase of rapid starch clearance and glucose absorption which occurs early in the meal. This conclusion was supported by the additional finding that rats conditioned faster after bilateral subdiaphragmatic vagotomy, when fat-free diets are cleared faster than in intact rats. This result also indicated that the conditioned oral stimuli did not reduce the satiating power of ingested nutrients via motor control of the stomach or by interacting with vagal afferent information.

Well-being in Rheumatoid Arthritis: The Effects of Disease Duration and Psychosocial Factors

This study examined the multivariate relationships of psychosocial factors with well-being in rheumatoid arthritis (RA). Fifty-five patients with early RA (< six months), 52 with intermediate RA (one-seven years) and 47 with established RA (> seven years) completed questionnaires on psychosocial factors and psychological and physical well-being. Illness perceptions related to worse depression and life satisfaction (especially in early RA) and to longer morning stiffness (especially in intermediate RA). Optimism related to lower pain in early and intermediate RA. Social support related to lower fatigue in established RA. Indications for interventions targeted by disease duration are discussed.

Modulation of the feeding response to peripheral insulin, 2-deoxyglucose or 3-O-methyl glucose injection.

The effects of circadian rhythm, delayed access to food, bilateral subdiaphragmatic vagotomy and bilateral adrenal medullectomy were examined. Like normal insulin injected subcutaneously, 2-deoxy-D-glucose injected intraperitoneally induces feeding in sated rats by night as well as by day. The unmetabolized glucose analogue 3-O-methyl-D-glucopyranose detectably increases feeding by day. On delayed return of food after 2-deoxyglucose injection into mildly deprived rats, feeding is at first inhibited and then facilitated. Vagotomy but not medullectomy interferes with 2-deoxyglucose-induced feeding, whereas medullectomy but not vagotomy interferes with insulin-induced feeding, when dosages near the optima for intact rats are used. However, when low doses are given, neither surgically induced deficit is evident.

Protein appetite demonstrated: Learned specificity of protein-cue preference to protein need in adult rats

After food had been withheld for 4 hours, casein was infused into the stomach of rats while they drank a distinctively flavored non-nutritive fluid. On testing under the same food-deprivation, the rats showed conditioned preference for the flavor. When protein was infused during the deprivation period before the test, they did not prefer the flavor, although they did when equicaloric carbohydrate had been pre-infused. These results demonstrate for the first time a learned hunger specifically for protein.