Hormonal and psychological factors linked to the increased thermic effect of food in malnourished fasting anorexia nervosa

Disordered eating in anorexia nervosa: give me heat, not just food

The recommendation to apply external heat to patients with anorexia nervosa (AN) was first documented by William Gull in 1874. Gull encountered this practice during his tenure as a consultant physician, responsible for issuing medical certifications for wealthy clients seeking admission to Ticehurst Asylum, one of the most successful and reputable private asylums in England. Gull attributed the origins of this practice to the studies by Charles Chossat (1796-1875), a physiologist, physician, and politician from Geneva, who discovered the therapeutic effects of heat on starved animals by chance. In the 20th century, further evidence of the beneficial effects of heat on starved animals emerged serendipitously when anomalies were observed following a malfunction in laboratory thermostats controlling animal temperatures. Moving into the 21st century, experimental research has empirically substantiated the crucial role of ambient temperature (AT) in the animal model of activity-based anorexia (ABA). Recent translational studies have shown that a warmed environment significantly reduces anxiety around mealtime in AN patients, a method shown to be more effective than exposure-based procedures. Despite the overwhelming evidence from both animal and patient studies, it is difficult to comprehend how the impact of providing a warm environment to AN patients, particularly around mealtimes, continues to be a neglected area of research.

Inpatient treatments for adults with anorexia nervosa: a systematic review of literature

PURPOSE

Anorexia nervosa (AN) is a mental disorder for which hospitalization is frequently needed in case of severe medical and psychiatric consequences. We aim to describe the state-of-the-art inpatient treatment of AN in real-world reports.

METHODS

A systematic review of the literature on the major medical databases, spanning from January 2011 to October 2023, was performed, using the keywords: "inpatient", "hospitalization" and "anorexia nervosa". Studies on pediatric populations and inpatients in residential facilities were excluded.

RESULTS

Twenty-seven studies (3501 subjects) were included, and nine themes related to the primary challenges faced in hospitalization settings were selected. About 81.48% of the studies detailed the clinical team, 51.85% cited the use of a psychotherapeutic model, 25.93% addressed motivation, 100% specified the treatment setting, 66.67% detailed nutrition and refeeding, 22.22% cited pharmacological therapy, 40.74% described admission or discharge criteria and 14.81% follow-up, and 51.85% used tests for assessment of the AN or psychopathology. Despite the factors defined by international guidelines, the data were not homogeneous and not adequately defined on admission/discharge criteria, pharmacological therapy, and motivation, while more comprehensive details were available for treatment settings, refeeding protocols, and psychometric assessments.

CONCLUSION

Though the heterogeneity among the included studies was considered, the existence of sparse criteria, objectives, and treatment modalities emerged, outlining a sometimes ambiguous report of hospitalization practices. Future studies must aim for a more comprehensive description of treatment approaches. This will enable uniform depictions of inpatient treatment, facilitating comparisons across different studies and establishing guidelines more grounded in scientific evidence.

LEVEL OF EVIDENCE

Level I, systematic review.

The Role of the Noradrenergic System in Eating Disorders: A Systematic Review

Noradrenaline (NE) is a catecholamine acting as both a neurotransmitter and a hormone, with relevant effects in modulating feeding behavior and satiety. Several studies have assessed the relationship between the noradrenergic system and Eating Disorders (EDs). This systematic review aims to report the existing literature on the role of the noradrenergic system in the development and treatment of EDs. A total of 35 studies were included. Preclinical studies demonstrated an involvement of the noradrenergic pathways in binge-like behaviors. Genetic studies on polymorphisms in genes coding for NE transporters and regulating enzymes have shown conflicting evidence. Clinical studies have reported non-unanimous evidence for the existence of absolute alterations in plasma NE values in patients with Anorexia Nervosa (AN) and Bulimia Nervosa (BN). Pharmacological studies have documented the efficacy of noradrenaline-modulating therapies in the treatment of BN and Binge Eating Disorder (BED). Insufficient evidence was found concerning the noradrenergic-mediated genetics of BED and BN, and psychopharmacological treatments targeting the noradrenergic system in AN. According to these data, further studies are required to expand the existing knowledge on the noradrenergic system as a potential target for treatments of EDs.

The Central Role of Hypothermia and Hyperactivity in Anorexia Nervosa: A Hypothesis

Typically, the development of anorexia nervosa (AN) is attributed to psycho-social causes. Several researchers have recently challenged this view and suggested that hypothermia and hyperactivity (HyAc) are central to AN. The following hypothesis will attempt to clarify their role in AN. Anorexia nervosa patients (ANs) have significantly lower core temperatures (T_core) compared to healthy controls (HCs). This reduced temperature represents a reset T_core that needs to be maintained. However, ANs cannot maintain this T_core due primarily to a reduced basal metabolic rate (BMR); BMR usually supplies heat to sustain T_core. Therefore, to generate the requisite heat, ANs revert to the behavioral-thermoregulatory strategy of HyAc. The majority of ANs (~89%) are reportedly HyAc. Surprisingly, engagement in HyAc is not motivated by a conscious awareness of low T_core, but rather by the innocuous sensation of "cold- hands" frequently reported by ANs. That is, local hand-thermoreceptors signal the brain to initiate HyAc, which boosts perfusion of the hands and alters the sensation of "cold-discomfort" to one of "comfort." This "rewarding" consequence encourages repetition/habit formation. Simultaneously, hyperactivity increases the availability of heat to assist with the preservation of T_core. Additionally, HyAc induces the synthesis of specific brain neuromodulators that suppress food intake and further promote HyAc; this outcome helps preserve low weight and perpetuates this vicious cycle. Based on this hypothesis and supported by rodent research, external heat availability should reduce the compulsion to be HyAc to thermoregulate. A reduction in HyAc should decrease the production of brain neuromodulators that suppress appetite. If verified, hopefully, this hypothesis will assist with the development of novel treatments to aid in the resolution of this intractable condition.

Short-term Outcomes of the Study of Refeeding to Optimize Inpatient Gains for Patients With Anorexia Nervosa: A Multicenter Randomized Clinical Trial

IMPORTANCE

The standard of care for refeeding inpatients with anorexia nervosa, starting with low calories and advancing cautiously, is associated with slow weight gain and protracted hospital stay. Limited data suggest that higher-calorie refeeding improves these outcomes with no increased risk of refeeding syndrome.

OBJECTIVE

To compare the short-term efficacy, safety, and cost of lower-calorie vs higher-calorie refeeding for malnourished adolescents and young adults with anorexia nervosa.

DESIGN, SETTING, AND PARTICIPANTS

In this multicenter randomized clinical trial with prospective follow-up conducted at 2 inpatient eating disorder programs at large tertiary care hospitals, 120 adolescents and young adults aged 12 to 24 years hospitalized with anorexia nervosa or atypical anorexia nervosa and 60% or more of median body mass index were enrolled from February 8, 2016, to March 7, 2019. The primary analysis was a modified intent-to-treat approach.

INTERVENTIONS

Higher-calorie refeeding, beginning at 2000 kcal/d and increasing by 200 kcal/d vs lower-calorie refeeding, beginning at 1400 k/cal and increasing by 200 kcal every other day.

MAIN OUTCOMES AND MEASURES

Main outcomes were end-of-treatment outcomes; the primary end point of this trial will be clinical remission over 12 months. Short-term efficacy was defined a priori as time to restore medical stability in the hospital, measured by the following 6 indices: 24-hour heart rate of 45 beats/min or more, systolic blood pressure of 90 mm Hg or more, temperature of 35.6 °C or more, orthostatic increase in heart rate of 35 beats/min or less, orthostatic decrease in systolic blood pressure of 20 mm Hg or less, and 75% or more of median body mass index for age and sex. The prespecified safety outcome was incidence of electrolyte abnormalities; cost efficacy was defined as savings associated with length of stay.

RESULTS

Because 9 participants withdrew prior to treatment, the modified intention-to-treat analyses included 111 participants (93%; 101 females [91%]; mean [SD] age, 16.4 [2.5] years). Higher-calorie refeeding restored medical stability significantly earlier than lower-calorie refeeding (hazard ratio, 1.67 [95% CI, 1.10-2.53]; P = .01). Electrolyte abnormalities and other adverse events did not differ by group. Hospital stay was 4.0 days shorter (95% CI, -6.1 to -1.9 days) among the group receiving higher-calorie refeeding, which was associated with a savings of $19 056 (95% CI, -$28 819 to -$9293) in hospital charges per participant.

CONCLUSIONS AND RELEVANCE

In the first randomized clinical trial in the US to compare refeeding approaches in patients with anorexia nervosa and atypical anorexia nervosa, higher-calorie refeeding demonstrated short-term efficacy with no increase in safety events during hospitalization.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02488109.

The effects of intranasal oxytocin on smoothie intake, cortisol and attentional bias in anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is characterised by severe malnutrition as well as intense fear and anxiety around food and eating with associated anomalies in information processing. Previous studies have found that the neuropeptide, oxytocin, can influence eating behaviour, lower the neurobiological stress response and anxiety among clinical populations, and alter attentional processing of food and eating related images in AN.

METHODOLOGY

Thirty adult women with AN and twenty-nine healthy comparison (HC) women took part in the current study. The study used double blind, placebo controlled, crossover design to investigate the effects of a single dose of intranasal oxytocin (40 IU) on a standard laboratory smoothie challenge, and on salivary cortisol, anxiety, and attentional bias towards food images before and after the smoothie challenge in AN and HC participants. Attentional bias was assessed using a visual probe task.

RESULTS

Relative to placebo intranasal oxytocin reduced salivary cortisol and altered anomalies in attentional bias towards food images in the AN group only. The oxytocin-induced reduction in attentional avoidance of food images correlated with oxytocin induced reduction in salivary cortisol in the AN group before the smoothie challenge. Intranasal oxytocin did not significantly alter subjective feelings of anxiety or intake during the smoothie challenge in the AN or HC groups.

CONCLUSIONS

Intranasal oxytocin may moderate the automated information processing biases in AN and reduce neurobiological stress. Further investigation of the effects of repeated administration of oxytocin on these processes as well as on eating behaviour and subjective anxiety would be of interest.

A systematic review of approaches to refeeding in patients with anorexia nervosa

OBJECTIVE

Given the importance of weight restoration for recovery in patients with anorexia nervosa (AN), we examined approaches to refeeding in adolescents and adults across treatment settings.

METHODS

Systematic review of PubMed, PsycINFO, Scopus, and Clinical Trials databases (1960-2015) using terms refeeding, weight restoration, hypophosphatemia, anorexia nervosa, anorexia, and anorexic.

RESULTS

Of 948 screened abstracts, 27 met these inclusion criteria: participants had AN; reproducible refeeding approach; weight gain, hypophosphatemia or cognitive/behavioral outcomes. Twenty-six studies (96%) were observational/prospective or retrospective and performed in hospital. Twelve studies published since 2010 examined approaches starting with higher calories than currently recommended (≥1400 kcal/d). The evidence supports 8 conclusions: 1) In mildly and moderately malnourished patients, lower calorie refeeding is too conservative; 2) Both meal-based approaches or combined nasogastric+meals can administer higher calories; 3) Higher calorie refeeding has not been associated with increased risk for the refeeding syndrome under close medical monitoring with electrolyte correction; 4) In severely malnourished inpatients, there is insufficient evidence to change the current standard of care; 5) Parenteral nutrition is not recommended; 6) Nutrient compositions within recommended ranges are appropriate; 7) More research is needed in non-hospital settings; 8) The long-term impact of different approaches is unknown;

DISCUSSION

Findings support higher calorie approaches to refeeding in mildly and moderately malnourished patients under close medical monitoring, however the safety, long-term outcomes, and feasibility outside of hospital have not been established. Further research is also needed on refeeding approaches in severely malnourished patients, methods of delivery, nutrient compositions and treatment settings.

Interacting Neural Processes of Feeding, Hyperactivity, Stress, Reward, and the Utility of the Activity-Based Anorexia Model of Anorexia Nervosa

Anorexia nervosa (AN) is a psychiatric illness with minimal effective treatments and a very high rate of mortality. Understanding the neurobiological underpinnings of the disease is imperative for improving outcomes and can be aided by the study of animal models. The activity-based anorexia rodent model (ABA) is the current best parallel for the study of AN. This review describes the basic neurobiology of feeding and hyperactivity seen in both ABA and AN, and compiles the research on the role that stress-response and reward pathways play in modulating the homeostatic drive to eat and to expend energy, which become dysfunctional in ABA and AN.

Postprandial metabolism in adults with Prader-Willi syndrome

OBJECTIVE

Individuals with Prader-Willi syndrome (PWS) are commonly restricted to 60-75% of height-appropriate calorie intake because they rapidly become obese on a normal diet. This study measured changes in energy expenditure, glucose and lipid homeostasis, and metabolic flexibility in response to a meal in PWS adults.

METHODS

11 adults with PWS were compared with 12 adiposity-matched and 10 lean subjects. Indirect calorimetry was conducted at baseline and 210 min after a standardized 600 kCal breakfast to assess energy expenditure and substrate utilization. Circulating glucose, insulin, C-peptide, glucagon, nonesterified fatty acids, and triglycerides were measured up to 240 min. Insulin sensitivity and insulin secretion rate were assessed by HOMA-IR and C-peptide deconvolution, respectively. Body composition was determined by dual-energy X-ray absorptiometry.

RESULTS

The PWS group had lower lean mass than the obesity control group. Corrected for lean mass, there were no differences between the PWS and obesity groups in resting metabolic rate or metabolic flexibility. Total and abdominal fat mass, insulin sensitivity, and insulin secretion rate were also similar between these groups.

CONCLUSIONS

This study did not detect an intrinsic metabolic defect in individuals with PWS. Rather, lower lean mass, combined with lower physical activity, may contribute to weight gain on an apparent weight-maintenance diet.

Association between resting energy expenditure, psychopathology and HPA-axis in eating disorders

AIM: To investigate the complex relationships between resting energy expenditure (REE), eating psychopathology, and Hypothalamus Pituitary Adrenal axis functioning in patients with eating disorders.

METHODS: The study was designed as a cross-sectional survey, and it was planned by the Clinic for Eating Disorders of the University of Florence (Italy). The protocol was approved by the Ethics Committee of the Institution. Twenty two anorexia nervosa and twenty one Bulimia Nervosa patients were assessed by means of a clinical interview and the structured clinical interview for diagnostic and statistical manual of mental disorders, fourth edition. Eating attitudes and behaviour were specifically investigated by means of the eating disorder examination questionnaire (EDE-Q). Patients were also evaluated by means of the symptom checklist (SCL 90-R), REE was measured by means of indirect calorimetry, and blood cortisol morning levels were evaluated.

RESULTS: Both anorexia nervosa and bulimia nervosa patients showed a reduced REE as compared with predicted REE. Body mass index (BMI) was positively associated with resting energy expenditure in Bulimics, whereas a strong, negative association between BMI and REE was observed in Anorectics. The pattern of associations between variables supported a mediation model, where shape concern accounted for variations in REE and cortisol levels (mediator), and variations in the mediator significantly accounted for variations in REE. When these associations where taken into account together, the relationship between shape concern and REE was no longer significant, whereas the association between cortisol levels and REE retained its significance, showing strong evidence for a single, dominant mediator. Anorectics and Bulimics showed an opposite pattern of association between BMI and REE. In Anorectics only, a higher REE was associated with a more severe eating disorder specific psychopathology, and cortisol levels represent a possible mediating factor for this relationship.

CONCLUSION: The data supported a mediation model where cortisol levels mediated the relationship between eating psychopathology (concern about body shape) and REE.

Anorexia nervosa: a rogue hibernation?

Anorexia nervosa is a puzzling and often tragic disorder which causes the individual to self starve and hyper-exercise. We present a speculative analysis of the disorder which begins by acknowledging and accepting the adaptation to flee famine theory. This theory holds that anorexia nervosa results from activation of an archaic pathway that functioned well during human's nomadic past. We advance this idea by suggesting that the faulty signal indicating there is a famine, arises from misalignment of the circadian/circannual oscillations. Entry and exit from hibernation is dependent on these cycles, and we draw an analogy between hibernation and anorexia nervosa. We offer ideas for testing the hypothesis, and targeting these faulty signals.

Nutritional rehabilitation in anorexia nervosa: review of the literature and implications for treatment

Restoration of weight and nutritional status are key elements in the treatment of anorexia nervosa (AN). This review aims to describe issues related to the caloric requirements needed to gain and maintain weight for short and long-term recovery for AN inpatients and outpatients.We reviewed the literature in PubMed pertaining to nutritional restoration in AN between 1960-2012. Based on this search, several themes emerged: 1. AN eating behavior; 2. Weight restoration in AN; 3. Role of exercise and metabolism in resistance to weight gain; 3. Medical consequences of weight restoration; 4. Rate of weight gain; 5. Weight maintenance; and 6. Nutrient intake.A fair amount is known about overall caloric requirements for weight restoration and maintenance for AN. For example, starting at 30-40 kilocalories per kilogram per day (kcal/kg/day) with increases up to 70-100 kcal/kg/day can achieve a weight gain of 1-1.5 kg/week for inpatients. However, little is known about the effects of nutritional deficits on weight gain, or how to meet nutrient requirements for restoration of nutritional status.This review seeks to draw attention to the need for the development of a foundation of basic nutritional knowledge about AN so that future treatment can be evidenced-based.

Increased hypothalamic-pituitary-adrenal drive is associated with decreased appetite and hypoactivation of food-motivation neurocircuitry in anorexia nervosa

OBJECTIVE

Corticotrophin-releasing hormone (CRH)-mediated hypercortisolemia has been demonstrated in anorexia nervosa (AN), a psychiatric disorder characterized by food restriction despite low body weight. While CRH is anorexigenic, downstream cortisol stimulates hunger. Using a food-related functional magnetic resonance imaging (fMRI) paradigm, we have demonstrated hypoactivation of brain regions involved in food motivation in women with AN, even after weight recovery. The relationship between hypothalamic-pituitary-adrenal (HPA) axis dysregulation and appetite and the association with food-motivation neurocircuitry hypoactivation are unknown in AN. We investigated the relationship between HPA activity, appetite, and food-motivation neurocircuitry hypoactivation in AN.

DESIGN

Cross-sectional study of 36 women (13 AN, ten weight-recovered AN (ANWR), and 13 healthy controls (HC)).

METHODS

Peripheral cortisol and ACTH levels were measured in a fasting state and 30, 60, and 120 min after a standardized mixed meal. The visual analog scale was used to assess homeostatic and hedonic appetite. fMRI was performed during visual processing of food and non-food stimuli to measure the brain activation pre- and post-meal.

RESULTS

In each group, serum cortisol levels decreased following the meal. Mean fasting, 120 min post-meal, and nadir cortisol levels were high in AN vs HC. Mean postprandial ACTH levels were high in ANWR compared with HC and AN subjects. Cortisol levels were associated with lower fasting homeostatic and hedonic appetite, independent of BMI and depressive symptoms. Cortisol levels were also associated with between-group variance in activation in the food-motivation brain regions (e.g. hypothalamus, amygdala, hippocampus, orbitofrontal cortex, and insula).

CONCLUSIONS

HPA activation may contribute to the maintenance of AN by the suppression of appetitive drive.

Higher calorie diets increase rate of weight gain and shorten hospital stay in hospitalized adolescents with anorexia nervosa

PURPOSE

Current recommendations for refeeding in anorexia nervosa (AN) are conservative, beginning around 1,200 calories to avoid refeeding syndrome. We previously showed poor weight gain and long hospital stay using this approach and hypothesized that a higher calorie approach would improve outcomes.

METHODS

Adolescents hospitalized for malnutrition due to AN were included in this quasi-experimental study comparing lower and higher calories during refeeding. Participants enrolled between 2002 and 2012; higher calories were prescribed starting around 2008. Daily prospective measures included weight, heart rate, temperature, hydration markers and serum phosphorus. Participants received formula only to replace refused food. Percent Median Body Mass Index (%MBMI) was calculated using 50th percentile body mass index for age and sex. Unpaired t-tests compared two groups split at 1,200 calories.

RESULTS

Fifty-six adolescents with mean (±SEM) age 16.2 (±.3) years and admit %MBMI 79.2% (±1.5%) were hospitalized for 14.9 (±.9) days. The only significant difference between groups (N = 28 each) at baseline was starting calories (1,764 [±60] vs. 1,093 [±28], p < .001). Participants on higher calories had faster weight gain (.46 [±.04] vs. .26 [±.03] %MBMI/day, p < .001), greater daily calorie advances (122 [±8] vs. 98 [±6], p = .024), shorter hospital stay (11.9 [±1.0] vs. 17.6 [±1.2] days, p < .001), and a greater tendency to receive phosphate supplementation (12 vs. 8 participants, p = .273).

CONCLUSIONS

Higher calorie diets produced faster weight gain in hospitalized adolescents with AN as compared with the currently recommended lower calorie diets. No cases of the refeeding syndrome were seen using phosphate supplementation. These findings lend further support to the move toward more aggressive refeeding in AN.

Nothing tastes as good as skinny feels: the neurobiology of anorexia nervosa

Individuals with anorexia nervosa (AN) engage in relentless restrictive eating and often become severely emaciated. Because there are no proven treatments, AN has high rates of relapse, chronicity, and death. Those with AN tend to have childhood temperament and personality traits, such as anxiety, obsessions, and perfectionism, which may reflect neurobiological risk factors for developing AN. Restricted eating may be a means of reducing negative mood caused by skewed interactions between serotonin aversive or inhibitory and dopamine reward systems. Brain imaging studies suggest that altered eating is a consequence of dysregulated reward and/or awareness of homeostatic needs, perhaps related to enhanced executive ability to inhibit incentive motivational drives. An understanding of the neurobiology of this disorder is likely to be important for developing more effective treatments.

A prospective examination of weight gain in hospitalized adolescents with anorexia nervosa on a recommended refeeding protocol

PURPOSE

Current refeeding recommendations for adolescents hospitalized with anorexia nervosa (AN) are conservative, starting with low calories and advancing slowly to avoid refeeding syndrome. The purpose of this study was to examine weight change and clinical outcomes in hospitalized adolescents with AN on a recommended refeeding protocol.

METHODS

Adolescents aged 13.1-20.5 years were followed during hospitalization for AN. Weight, vital signs, electrolytes, and 24-hour fluid balance were measured daily. Percent median body mass index (%MBMI) was calculated as 50th percentile BMI for age and gender. Calories were prescribed on admission and were increased every other day.

RESULTS

Thirty-five subjects with a mean (SD) age of 16.2 (1.9) years participated over 16.7 (6.4) days. Calories increased from 1,205 (289) to 2,668 (387). No subjects had refeeding syndrome; 20% had low serum phosphorus. Percent MBMI increased from 80.1 (11.5) to 84.5 (9.6); overall gain was 2.10 (1.98) kg. However, 83% of subjects initially lost weight. Mean %MBMI did not increase significantly until day 8. Higher calories prescribed at baseline were significantly associated with faster weight gain (p = .003) and shorter hospital stay (p = .030) in multivariate regression models adjusted for %MBMI and lowest heart rate on admission.

CONCLUSIONS

Hospitalized adolescents with AN demonstrated initial weight loss and slow weight gain on a recommended refeeding protocol. Higher calorie diets instituted at admission predicted faster weight gain and shorter hospital stay. These findings support the development of more aggressive feeding strategies in adolescents hospitalized with AN. Further research is needed to identify caloric and supplementation regimens to maximize weight gain safely while avoiding refeeding syndrome.

Heat makes a difference in activity-based anorexia: a translational approach to treatment development in anorexia nervosa

OBJECTIVE

To test the effect of raising ambient temperature (AT) on activity-based anorexia (ABA) and to extend to female rats previous findings reported in male animals.

METHOD

Two studies are reported in which female rats were submitted to food restriction and free access to an activity wheel either separately or in combination under changing (21-32 °C) or constant AT (21 °C).

RESULTS

Warming ABA animals reversed running activity, preserved food-intake, and enabled female rats to recover from acute weight loss. Moreover, sedentary food-restricted warmed rats maintained a body weight equivalent to the levels of animals housed at standard AT in spite of 20% reduced food-intake.

DISCUSSION

The replication on female rats corroborates the effect previously reported for males, which is indicative of the robust effect of AT in recovering rats from ABA. The findings reported here represent strong preclinical evidence in favor of heat supply as a useful adjunctive component for the treatment of anorexia nervosa (AN).

Can eating disorders cause functional gastrointestinal disorders?

Functional gastrointestinal disorders (FGIDs) are very common (up to 98%) in patients with an eating disorder (ED). Boyd et al. discuss in this issue of Neurogastroenterology & Motility that FGIDs can persist independently on the outcome of the ED. Their findings leave room for speculation on the mechanisms underlying FGIDs in patients with an ED. FGIDs result from a complex interaction of biological, psychosocial and social factors. The altered eating behavior seen in EDs is strongly associated with disturbed gastrointestinal sensitivity and motor physiology. Moreover, psychiatric co-morbidities in ED patients are also frequently found in FGIDs. The motor and sensitivity disturbances together with psychiatric co-morbidities can lay the foundation of a FGID. Once established the psychological and physiological disturbances can perpetuate and strengthen each other resulting in a FGID that can persist independently of the ED that originally caused the motor and sensitivity disturbances.

Experience with activity based anorexia enhances conditioned taste aversion learning in rats

Activity based anorexia (ABA) is a model that mimics the self-starvation and hyperactivity features of anorexia nervosa (AN). This study investigated whether a history of ABA will enhance food avoidance learning and retard its extinction in female rats. We compared the acquisition and extinction of a conditioned taste aversion (CTA) in naive (ad lib with no access to RW), ABA, and pair-fed to the food intake of ABA (with access to a locked RW) female Sprague-Dawley rats. The CTA conditioning was conducted after the ABA and pair-fed rats had recovered to their pre-food restriction body weights. For the CTA learning, 0.3M sucrose consumption was followed by low doses LiCl (0.009M or 0.018M at 1.33ml/100g of body weight, IP) injection. The results revealed that the ABA rats acquired an aversion to sucrose significantly sooner than the naive controls. Furthermore, they completely avoided sucrose while the naive and pair-fed controls still sampled it by the end of 10 conditioning trials. When extinction was assessed by 1-bottle and 2-bottle tests, the ABA rats extinguished more slowly than the controls. However, the differences in sucrose aversion extinction between the ABA and control rats were only significant in the 1-bottle test. These data suggest that experience with AN-like behaviors results in an acquired aversion to a preferred food sooner and a longer retention of the negative food associations. These findings have implications for understanding the persistence of aberrant eating behaviors in eating disorders.

Transcranial direct current stimulation in the treatment of anorexia

Transcranial direct current stimulation (tDCS) is a non-invasive technique for brain stimulation and it increasingly being used in the treatments of some neurological/psychiatric conditions (e.g. chronic pain, epilepsy, depression, motor rehabilitation after stroke and Parkinson's disease). With tDCS, cortical neurons excitability increases in the vicinity of the anodal electrode and suppressed near the cathodal electrode. There is evidence that anorexia is associated with hyperactivity in right-hemisphere frontal regions. tDCS, therefore has a promising potential in facilitating inter-hemispheric balance. A tDCS protocol is proposed: the anode electrode placed over the left prefrontal cortex and the cathode electrode located, either on the right homotopic region for non-SSRI-medicated anorexics, or on a non-cephalic site for SSRI-medicated anorexics. Together with nutritional supplements, psychotherapy and other treatments, tDCS have a good potential, as a complementary tool, in the treatment of anorexia.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Heat reversal of activity-based anorexia: implications for the treatment of anorexia nervosa

OBJECTIVE

Activity-based anorexia (ABA) provides an animal model of anorexia nervosa (AN). In this model, rats given restricted access to food but unrestricted access to activity wheels, run excessively while reducing food intake, lose a sizeable percentage of body weight, become hypothermic, and can fail to recover unless removed from these conditions.

METHOD

Once rats had lost 20% of body weight under standard ABA conditions, they were assigned to one of two ambient temperature (AT) conditions.

RESULTS

Increased AT reduced running rates and led to weight gain in active rats. The effect of increasing AT on food intake was dependent on whether the rats were sedentary or active. Although warming reduced food intake in the sedentary rats their body weight remained stable, whereas in active rats increased AT did not reduce food intake and weight gain gradually rose.

CONCLUSION

From a translational perspective, these findings offer a fresh perspective to the disorder, and underscore the need for further studies to assess the effects of heat treatment in patients as an innovative adjunctive treatment for anorexia nervosa.