Harvey P. Weingarten

Food cravings in a college population

A questionnaire was administered to over 1000 male and female college undergraduates to collect self-reports regarding food cravings (defined as an intense desire to eat a specific food). Ninety-seven per cent of woman and 68 per cent of men reported experiencing food cravings. Chocolate was the most frequently reported food craved, especially among women. The majority of subjects reported that they indulged their food cravings at least half the time. Females tended to respond with more negative affect to indulging their cravings than men. Only 32 per cent of women perceived that their cravings were linked to menstrual cycles. There was no tendency for an increase in food cravings with dietary restraint. The data provided a detailed description of perceptions regarding food cravings among college-age adults, but also underscored some of the limitations of self-report measures of food craving. In spite of these limitations, however, the results challenge several assumptions regarding food craving and highlight some promising avenues for future investigation.

The phenomenology of food cravings

A craving for specific foods represents one of the most common and intense experiences surrounding eating. This paper explores the phenomenology of food craving by discussing the properties, origins and determinants of the craving state. The discussion includes consideration of the use of the craving concept in the drug literature and a review of the food craving literature. It is suggested that advances in the understanding of food cravings must address the problem of the definition and measurement of the craving state and proceed with recognition of the inadequacies of the ubiquitous assumption that cravings serve to identify and redress bodily needs.

Previous inflammation alters the response of the rat colon to stress

BACKGROUND & AIMS Patients with inflammatory bowel disease have symptoms of irritable bowel syndrome (IBS) with a higher than expected prevalence. Stress is an important factor in the pathogenesis of IBS. Thus, previous inflammation may predispose to IBS by rendering the bowel more susceptible to the impact of stress. The aim of this study was to examine the effect of previous colitis on stress-induced responses in rats. METHODS Acute colitis was induced in rats by intrarectal administration of trinitrobenzene sulfonic acid (TNBS), and the rats were allowed to recover for 6 weeks before application of mild restraint stress for 3 consecutive days. In vitro measurements included myeloperoxidase activity, plasma corticosterone levels, interleukin 1 beta messenger RNA expression, and [3H]noradrenaline release from the myenteric plexus. RESULTS Six weeks after administration of TNBS, stress caused a significant increase in myeloperoxidase activity in TNBS-treated rats but not in stressed controls; plasma corticosterone responses were similar. Stress also caused an exaggerated and significant suppression of [3H]noradrenaline release in TNBS-treated stressed rats compared with stressed controls. This was accompanied by a significant decrease in interleukin 1 beta messenger RNA expression in the colon. CONCLUSIONS Previous colitis rendered the colon more susceptible to effects of stress on enteric nerve function and also increased some parameters of inflammation in response to stress.

Sham feeding as a procedure for assessing the influence of diet palatability on food intake.

Most of the methods used to evaluate the role of taste factors on food intake are confounded by the postingestional consequences of the ingested diet which interfere with measurements of consumption based strictly upon the stimulus properties of the food. The present experiment examines the utility of sham feeding in the gastric fistulated rat as a means of isolating, and thereby evaluating, the contribution of hedonically positive (sweet) and hedonically negative (bitter) taste factors on the magnitude of food intake. Rats equipped with open gastric cannulae sham fed solutions varying in their sucrose or quinine concentrations. The results revealed that the magnitude of sham feeding in a fixed time period varied systematically with the taste properties of the food. It is concluded that sham feeding represents a useful technique for isolating the influence of diet palatability on food intake. Furthermore, the present data identify one of the parameters that influences the magnitude of the sham feeding response, information that is important for studies using this preparation as a means of examining oral sensory controls of food intake control systems.

Meal initiation controlled by learned cues: basic behavioral properties.

The behavioral properties of meals initiated in response to the presentation of food-associated external stimuli are examined. A Pavlovian conditioning procedure was used to teach animals an association between an arbitrary external cue and food. Subsequent presentations of the conditioned cue reliably led to the initiation of feeding even though rats were tested under conditions of satiety. Several properties of learned external control of feeding were identified. First, the size of meals motivated by exposure to signals for food resembled the level of ingestion characteristic of spontaneous feeding. Second, the potency of externally-controlled intake was influenced by satiety signals arising from previous meals. Third, although presentation of the conditioned cue could be used to influence meal pattern, rats regulated the amount of calories consumed in a 24-h period. These results establish that learning contributes to meal initiation and that mechanisms based on learning do not require (but may interact with) internal energy depletion signals in the control of feeding. The implications of these findings to models of feeding behavior are discussed.

Comparison of the metabolic and behavioral disturbances following paraventricular- and ventromedial-hypothalamic lesions

Lesions of the ventromedial hypothalamus (VMH) result in an obesity syndrome with several metabolic and behavioral manifestations. It has also been reported that damage to the paraventricular hypothalamus (PVH) leads to changes characteristic of obesity. However, little is known about the consequence of PVH lesions, especially in contrast to the extensive documentation of VMH lesion-induced effects. To assess the basic features of the two hypothalamic obesity syndromes, rats underwent VMH, PVH, or sham lesions and, for 15 weeks, were maintained ad lib on a series of test diets. Both lesions groups were hyperphagic and showed similar weight gains. Although both lesion groups became obese (measured by % carcass fat), VMH rats were fatter than PVH animals. Similarly, only VMH rats were hyperinsulinemic. Further tests were conducted in PVH and VMH rats restricted to control body weights. VMH, but not PVH, rats developed a persisting elevation in basal gastric acid secretion. As well, only VMH, and not PVH, animals developed an obesity when restricted to normal weights. These data indicate similarities in PVH and VMH rats maintained ad lib but experiments on restricted animals reveal fundamental differences in the two obesities and point to different etiologies.

Hedonic response of sucrose likers and dislikers to other gustatory stimuli

The majority of individuals can be classified as sweet likers or dislikers based on their hedonic (pleasure) response to sucrose solutions of varying concentrations. Our results indicate that the sweet liker/disliker distinction generalizes to sugars other than sucrose, i.e., glucose and fructose. As well, these individual hedonic response patterns are maintained even when a flavor and color are added to sucrose solutions. However, whether one is a sweet liker or disliker does not predict hedonic response to nonsweet tastes such as salt. These results indicate that the sweet liker/disliker distinction is a robust phenomenon which appears to generalize over, but is restricted to, sweet-tasting substances. The possibility that individual differences in hedonic response may predict preferences for, and intake of, complex tastes characteristic of foods encountered in the real world, is discussed.

Meal initiation controlled by learned cues: Effects of peripheral cholinergic blockade and cholecystokinin

Sated animals can be induced to initiate meals by exposing them to external stimuli which they have learned, via Pavlovian conditioning, to associate with food. This study examined physiological properties of this control of feeding. The initial hypothesis examined was that conditioned feeding depended on the elaboration of cholinergic cephalic phase responses (e.g., anticipatory insulin secretion). This idea was evaluated by comparing feeding responses to presentation of conditioned cues following an injection of either a peripheral cholinergic blocker, atropine methyl nitrate, or a control substance, physiological saline. Peripheral cholinergic blockade had no effect on the meal initiated by presentation of conditioned cues even though the dose of atropine methyl nitrate used was demonstrated to be sufficient to completely suppress cholinergic cephalic phase responses. These results indicate that cholinergic anticipatory digestive secretions do not contribute to feeding in this preparation. The effects of exogenously administered cholecystokinin on feeding controlled by learned cues were also studied. Cholecystokinin suppressed the size of the meal induced by presentation of conditioned stimuli but did not influence the latency, or initial rate of eating. The implications of these results to a conclusion that cholecystokinin is a satiety factor are discussed.

Taste-to-postingestive consequence conditioning: Is the rise in sham feeding with repeated experience a learning phenomenon?

Although the progressive increase in intake with repeated sham feeding experience is assumed to reflect the extinction of learned satiety, the involvement of associative learning in this phenomenon has never been directly demonstrated. We show that: a) animals attenuate sham feeding on initial exposure only with foods tasting like those they have fed normally before, and b) latent inhibition, which retards the formation of CS-US associations in classical conditioning preparations, prevents the association of a taste with its postingestive consequences. These data suggest both that learning plays a role in the development of sham feeding and that associative linking of a foods taste with its postingestive consequences occurs during ingestion. The present results identify properties of taste-to-postingestive consequence conditioning and indicate how the sham feeding preparation can be used to identify the physiological events mediating this learning.

Fos-like immunoreactivity in vagal and hypoglossal nuclei in different feeding states: a quantitative study.

This study characterized the distribution of Fos-like immunoreactivity (FLI) in three hindbrain nuclei: dorsal motor nucleus of the vagus (DMN), nucleus of the solitary tract (NST) and hypoglossal nucleus (HG) in response to eating or activation of specific components of feeding behavior. The degree of FLI was quantified by automated image analysis software that provided an efficient and sensitive method for counting the number of cells labelled with Fos antibody. Ingestion, and anticipation, of a meal both increased FLI in the DMN and HG, but not in the NST. Sham feeding 1 M sucrose was a more potent stimulus for FLI activation in DMN and NST than combined oral plus gastric/postingestive stimulation provided by real feeding the same food. The results indicate that the physiological stimulus of eating is sufficient to elicit FLI in the hindbrain and that specific components of the feeding act, especially oral stimulation provided by sham feeding, can activate FLI. The results suggest further that, under specific experimental conditions, gastric and/or postgastric stimulation may decrease FLI in the NST and DMN.