Whole body lipid oxidation during exercise is impaired with poor insulin sensitivity but not with obesity per se.

Equivocal findings regarding the influence of overweight/obesity on exercise lipid-oxidizing capacity (EX-LIPOX) might reflect inadequate control of 1) acute energy balance/macronutrient composition of diet; 2) intensity/duration of exercise; and/or 3) insulin sensitivity (IS) of participant. To assess independent/combined influences of IS and overweight/obesity with other factors controlled, we recruited sedentary adults with normal weight (NW; n = 15) or overweight/obesity (O; n = 15) subdivided into metabolically healthy (MH; n = 8) and unhealthy (MU; n = 7) groups (IS; MH > MU). Participants completed a 9-day, weight-stabilizing, controlled-feeding protocol comprising measurements of resting metabolism, body composition, oral glucose tolerance, and maximal exercise capacity. We measured EX-LIPOX during the initial 45 min of "steady state" during constant-work-rate cycling at 70% and 100% of participant gas-exchange threshold (GET). At 70%, average EX-LIPOX in absolute (0.11 ± 0.02 g·min-1) and relative (2.4 ± 0.3 mg·kgFFM-1·min-1) terms was lower for NW-MU than MH regardless of body composition (NW-MH, 0.19 ± 0.02 g·min-1/3.9 ± 0.3 mg·kgFFM-1·min-1; O-MH, 0.19 ± 0.02 g·min-1/3.7 ± 0.3 mg·kgFFM-1·min-1), whereas no difference was present for NW-MU and O-MU (0.15 ± 0.02 g·min-1/2.8 ± 0.3 mg·kgFFM-1·min-1). Multiple regression confirmed that with IS-controlled, overweight/obesity was not associated with decreased EX-LIPOX, whereas decreased EX-LIPOX was associated with decreased IS independent of overweight/obesity. Overweight/obesity also did not influence EX-LIPOX across MH groups or with cohort divided by body-composition classification alone (P > 0.05). Exercise lipid-oxidizing capacity is impaired with poor IS regardless of body composition, but not with overweight/obesity per se.NEW & NOTEWORTHY In this study, we have shown that the capacity to oxidize lipid during exercise is influenced by metabolic health of the exerciser regardless of body composition, but not by body composition per se. This observation refutes the belief that a reduced capacity to oxidize lipid is an obligatory characteristic of the overweight/obese condition while supporting the contention that exercise should be prescribed with specificity based on both absence/presence of overweight/obesity and compromise/lack thereof in metabolic health.

The Universal Eating Monitor (UEM): objective assessment of food intake behavior in the laboratory setting.

The Universal Eating Monitor was a term used to describe a device used in a laboratory setting that enabled investigators to measure, with the same instrument, the rate of eating either solids or liquids, hence the term "universal". It consisted of an electronic balance placed in a false panel under a table cloth on which could be placed a food reservoir that contained either solid or liquefied food. The device was created in order to determine whether rates of eating differed in pattern between solid and liquid foods. An acceptable mixture of foods of identical composition that could be served as either solid or blended as a liquid was used to test the hypothesis that eating rate and intake were affected by physical composition. A best-fitting mathematical function (intake was quadratic function of time, with coefficients varying among foods used and experimental conditions), quantified intake rates. The device was used to test a variety of mechanisms underlying food intake control. Eating rates were linear when solid foods were used, but negatively accelerated with liquids. Overall, intake did not differ between solid and liquefied food of identical composition. Satiation on a calorie for calorie basis was different among foods, but physical composition interacted with energy density. Hormones and gastric distension were strong influences on food intake and rate of eating. Individuals with bulimia nervosa and binge eating disorder ate more than individuals without these disturbances. Intake in social and individual contexts was identical, but the rate of eating was slower when two individuals dined together. The eating monitor has been a useful instrument for elucidating controls of food intake and describing eating pathology.

Preoperative liking and wanting for sweet beverages as predictors of body weight loss after Roux-en-Y gastric bypass and sleeve gastrectomy.

BACKGROUND/OBJECTIVES: Patients who receive Roux-en-Y gastric bypass (RYGB) lose more weight than those who receive vertical sleeve gastrectomy (VSG). RYGB and VSG alter hedonic responses to sweet flavor, but whether baseline differences in hedonic responses modulate weight loss after RYGB or VSG remains untested. PARTICIPANTS/METHODS: Male and female candidates (n = 66) for RYGB or VSG were recruited and tested for their subjective liking and wanting ratings of sucrose solutions and flavored beverages sweetened with aspartame. Participants were classified by unsupervised hierarchical clustering for their liking and wanting ratings of sucrose and aspartame. Participant liking ratings were also used in a supervised classification using pre-established categories of liking ratings (liker, disliker, and inverted u-shape). Effects of categories obtained from unsupervised or supervised classification on body weight loss and their interaction with surgery type were analyzed separately at 3 and 12 months after surgery using linear models corrected for sex and age. RESULTS: RYGB participants lost more body weight compared with VSG participants at 3 and 12 months after surgery (P < 0.001 for both time points). Unsupervised clustering analysis identified clusters corresponding to high and low wanting or liking ratings for sucrose or aspartame. RYGB participants in high-wanting clusters based on sucrose, but not aspartame, lost more weight than VSG at both 3 (P = 0.01) and 12 months (P = 0.03), yielding a significant cluster by surgery interaction. Categories based on supervised classification using liking ratings for sucrose or aspartame showed no significant effects on body weight loss between RYGB and VSG participants. CONCLUSIONS: Classification of patients into high/low-wanting ratings for sucrose before surgery can predict differential body weight loss after RYGB or VSG in adults and could be used to advise on surgery type.

Combined effects of cholecystokinin-8 and gastric distension on food intake in humans.

In a previous study (Kissileff HR, Carretta JC, Geliebter A, Pi-Sunyer FX. Am J Physiol Regul Integr Comp Physiol 285: R992-R998, 2003), when subthreshold gastric distension (300 ml) and a low dose of cholecystokinin octapeptide (CCK-8) (112 ng/min for 21 min) were concurrently administered to human participants, intake of a test meal was significantly reduced. However, the supra-additive interaction of CCK-8 and gastric distension was not significant. The purpose of the present study was to determine whether a significant interaction would be obtained when CCK-8 and gastric distension were each increased by 50% above levels used in the previous study. Twelve normal-weight, healthy participants were tested four times each with either CCK-8 (168 ng/min for 30 min) or saline infusion crossed with gastric distension (450 ml) or no distension. The combination of CCK-8 and gastric distension reduced food intake by a mean of 405 ± 86 g (SE) in comparison with the saline nondistension condition (P < 0.001), which is a 51% reduction. Although there were some differences in the protocols, the combined effect was double that seen in the previous study. Although the interactive effect was larger [118 ± 109 g (SE)] than it was previously [73 ± 86 (SE)], it was not significant (P = 0.29). There were also reports of a short-lived sick feeling after CCK-8, with and without distension, that was not observed in the previous study. Thus the combination of CCK-8 at 1.5 times threshold and gastric distension at 450 ml (increased from 300 ml) resulted in a combined effect to reduce food intake, which was also 1.5 times its previous value, and thus appears linear.

Food portion size area mediates energy effects on expected anxiety in anorexia nervosa.

A study in which adolescent patients with anorexia nervosa (n = 24) rated their expected food-anxiety in response to images of portions of food (potatoes, rice pizza, and M&Ms) showed that lower energy-dense foods elicited higher expected anxiety per kilocalorie than higher energy-dense foods. However, the area of the portion sizes could be an unmeasured variable driving the anxiety response. To test the hypothesis that area mediates the effects of energy content on expected anxiety, the same images of portions were measured in area (cm2), and standardized values of expected anxiety were regressed from standardized values of energy and area of portions. With regression of expected anxiety from portion size in area, M&Ms, which had the highest energy density of the four foods, elicited the highest expected anxiety slope (ß = 1.75), which was significantly different from the expected anxiety slopes of the other three foods (ß range = 0.67 - 0.96). Area was confirmed as a mediator of energy effects from loss of significance of the slopes when area was added to the regression of expected anxiety from energy x food. When expected anxiety was regressed from food, area, energy and area by energy interaction, area accounted for 5.7 times more variance than energy, and ß for area (0.7) was significantly larger (by 0.52, SE = 0.15, t = 3.4, p = 0.0007) than ß for energy (0.19). Area could be a learned cue for the energy content of food portions, and thus, for weight gain potential, which triggers anxiety in patients with anorexia nervosa.

Self-reported emotional eaters consume more food under stress if they experience heightened stress reactivity and emotional relief from stress upon eating.

Group data means from individuals who self-assess as emotional eaters do not reliably show increased food intake in response to stress or negative emotions. This inconsistency in predictive validity of self-reported emotional eating (EE) could be attributable to unconsidered moderation of the relationship between self-reported EE and behavioral measures of EE. Greater emotional relief from stress by eating may provide enhanced negative reinforcement and promote future EE in response to stress as a form of self-medication. Thus, we predicted that greater emotional relief from stress by eating (decrease in negative affect from stress to post-eating) would moderate the extent to which heightened stress reactivity (measured by systolic blood pressure, SBP) moderates the relationship between self-reported EE and food intake post-stress. We also hypothesized that self-reported EE would not predict greater food consumption on the rest day. 43 undergraduate women completed online assessments of eating behaviors. Participants were given snacks to eat after a mental stress task (TSST) or rest period on separate days in counterbalanced order. Our prediction was supported, as the moderated moderation model (PROCESS model 3) was highly significant on the stress day. Self-reported EE predicted increased food intake post-stress only under conditions of high stress reactivity and high emotional relief. On the rest day, self-reported EE predicted greater snack food intake only when SBP was high. This conditional increased intake substantiates stress as a promoter of snack food consumption for women with greater EE. Overall, our findings identified factors that may distinguish the subset of self-reported emotional eaters who are more likely to display EE behaviors in a laboratory setting, yet further studies are needed to directly test whether negative reinforcement via emotional relief from stress by eating drives enhanced EE following stress.

Comparison of Interview to Questionnaire for Assessment of Eating Disorders after Bariatric Surgery.

The Eating Disorder Examination Interview Bariatric Surgery Version (EDE-BSV) assesses eating pathology after bariatric surgery but requires significant training and time to administer. Consequently, we developed a questionnaire format called the Eating Disorders After Bariatric Surgery Questionnaire (EDABS-Q). This study evaluates the consistency of responsiveness between the two formats. After surgery, 30 patients completed the EDE-BSV and EDABS-Q in a restricted randomized design. Patient reported behavior for each item which was converted to a score following the Eating Disorder Examination-Questionnaire (EDE-Q) scoring scheme. Responses fell into three distributions: (1) dichotomous, (2) ordinal, or (3) unimodal. Distributions of items were not different between the two formats and order did not influence response. Tests of agreement (normal approximation of the binomial test) and association (χ2 analyses on binary data and spearman rank order correlations on ordinal items) were performed. Percent concordance was high across items (63-100%). Agreement was significant in 31 of 41 items (Bonferroni-P < 0.001). Association was significant in 10 of 21 in χ2-appropriate items (Bonferroni-P < 0.002), and the ordinal items had highly significant correlations between formats (Bonferroni-P < 0.0125). The EDABS-Q is an adequate substitute for the EDE-BSV and may be useful for research and clinical evaluation of eating pathology after bariatric surgery.

Recalled and momentary virtual portions created of snacks predict actual intake under laboratory stress condition.

Virtual portion tasks have been used to predict food intake in healthy individuals, severity of illness in individuals with anorexia nervosa, and weight loss in bariatric surgery patients. Whether portion creation in response to a recalled interpersonal stress ("recalled stress portions") could be used as a proxy for ad lib intake, after a stressor, remains untested, and the mechanism supporting this relationship is unclear. The present study's goals were: 1) to validate virtual portion tasks as proxies for actual food intake in a stressful context and 2) to test a causal pathway in which these virtual stress portions predict ad lib intake after stress. We proposed that this relationship is mediated by virtual portions created the moment after laboratory stress or rest manipulation (momentary portions), and before the participant actually ate food. At screening, 29 healthy undergraduate white women created virtual portions of eight snacks (apples, olives, potato chips, pretzels, caramel popcorn, milk chocolate) that they typically eat and also portions they recall eating in response to a stressful interpersonal situation. In addition, after a Trier Social Stress Test, or a rest period, on separate days in counterbalanced order, participants created 'momentary' virtual portions of the same snacks presented during screening, and then were given potato chips, mini golden Oreos, and M&Ms to eat. Recalled stress (b = 0.07 ± 0.02, p = 0.003), and momentary stress (b = 0.12 ± 0.02, p = 0.00001), portions of milk chocolate accounted for 29% and 51%, respectively, of the variance in ad lib stress intake of M&Ms. Typical (b = 0.15 ± 0.07, p = 0.03), and momentary rest (b = 0.21 ± 0.06, p = 0.002), portions of chips accounted for 16% and 31%, respectively, of the variance in ad lib rest intake of chips. The causal pathway from recalled stress portion to ad lib stress snack intake was completely mediated by momentary stress portion for milk chocolate and M&Ms (ß = 0.04 ± 0.02, z = 2.4, p = 0.0154). These findings illustrate the planning and recall components of eating in response to stress, but not necessarily under rest conditions. This recalled stress virtual portion paradigm has clinical and research value in that it can detect those who overconsume in response to stress.

Reliability and responsiveness of virtual portion size creation tasks: Influences of context, foods, and a bariatric surgical procedure.

Food portion size influences energy intake and sustained high-energy intake often leads to obesity. Virtual portion creation tasks (VPCTs), in which a participant creates portions of food on a computer screen, predict intake in healthy individuals. The objective of this study was to determine whether portions created in VPCTs are stable over time (test-retest reliability) and responsive to factors known to influence food intake, such as eating contexts and food types, and to determine if virtual portions can predict weight loss. Patients with obesity scheduled for bariatric surgery (n = 29), and individuals with a normal BMI (18.5-24.9 kg/m2, controls, n = 29), were instructed to create virtual portions of eight snack foods, which varied in energy density (low and high) and taste (sweet and salty). Portions were created in response to the following eating situations, or "contexts": What they would a) eat to stay healthy (healthy), b) typically eat (typical), c) eat to feel comfortably satisfied (satisfied), d) consider the most that they could tolerate eating (maximum), and e) eat if nothing was limiting them (desired). Tasks were completed before, and 3 months after, surgery in patients, and at two visits, 3 months apart, in controls. Body weight (kg) was recorded at both visits. Virtual portions differed significantly across groups, visits, eating contexts, energy densities (low vs. high), and tastes (sweet vs. salty). Portions created by controls did not change over time, while portions created by patients decreased significantly after surgery, for all contexts except healthy. For patients, desired and healthy portions predicted 3-month weight loss. VPCTs are replicable, responsive to foods and eating contexts, and predict surgical weight loss. These tasks could be useful for individual assessment of expectations of amounts that are eaten in health and disease and for prediction of weight loss.

The development of hunger and fullness during a laboratory meal in patients with binge eating disorder.

OBJECTIVE: This study aimed to test the hypothesis that, compared to similarly obese participants without BED, individuals with BED have a disturbance in the development of fullness and reduction of hunger during the course of a standard meal of large size. METHOD: Thirteen patients with BED and 14 obese control participants consumed 975 g of a milkshake. Participants received no information about how much they had eaten or how much of the meal remained to be consumed. Participants were interrupted after every 75 g consumed to rate hunger and fullness. RESULTS: Final fullness ratings were higher in patients with BED, but there were no differences in mean duration or mean rate of eating, or in changes in subjective ratings of hunger and fullness per gram of food. DISCUSSION: The current study reports the surprising finding of no difference in reports of hunger and fullness between patients with BED and obese controls.

Negative affect is associated with increased stress-eating for women with high perceived life stress.

Perceived life stress (PLS) and cognitive restraint are associated with increased comfort food intake under stress and lead to weight gain and obesity, but the mechanisms by which they do so remain unclear. Stress and negative affect (NA) are associated with increased reward-driven comfort food intake as a means to 'feel better', particularly for individuals with higher PLS and cognitive restraint. Thus, we propose that PLS and cognitive restraint increase stress-eating by strengthening the relationship between stress-induced NA and comfort food intake. Upon comfort eating, individuals with higher PLS show greater reductions in the negative consequences of stress (e.g. NA). The rewarding effects of this 'emotional relief' may promote future stress-induced comfort eating, but this has yet to be examined. Thus, we investigate the pathways by which PLS or cognitive restraint increase snack intake under stress by proposing that 1) stress-induced NA is a stronger predictor of increased snack intake for women with greater PLS and cognitive restraint, and 2) greater PLS will be associated with greater reductions in NA upon snacking under stress (i.e. emotional relief). Forty-three healthy women were given snacks (chips, golden oreos, and M&Ms) to eat after a Trier Social Stress Test or rest period on separate days in counterbalanced order. Following linear regression analyses, we determined that stress-induced NA predicted more snack intake for women with higher PLS, and that higher PLS was associated with heightened emotional relief upon snacking under stress. Future studies are needed to directly assess whether greater emotional relief following stress-eating reinforces the learned association between stress-induced NA and intake, and ultimately explains greater stress-eating and obesity in women with higher PLS. This work may lead clinicians to focus on NA in the treatment of obesity-and stress-related illnesses for women with higher PLS.

Effect of eating rate on binge size in Bulimia Nervosa.

Bulimia Nervosa (BN) is an eating disorder characterized by recurrent episodes of binge eating. During binge eating episodes, patients often describe the rapid consumption of food, and laboratory studies have shown that during binges patients with BN eat faster than normal controls (NC), but the hypothesis that a rapid rate of eating contributes to the excessive intake of binge meals has not yet been experimentally tested. The aim of this study was to assess the effect of eating rate on binge size in BN, in order to determine whether binge size is mediated, in part, by rate of eating. Thirteen BN and 14 NC subjects were asked to binge eat a yogurt shake that was served at a fast rate (140 g/min) on one occasion and at a slow rate (70 g/min) on another. NC subjects consumed 169 g more when eating at the fast rate than when eating at the slow rate. In contrast, consumption rates failed to influence binge size in patients with BN (fast: 1205 g; slow: 1195 g). Consequently, there was a significant group by rate interaction. As expected, patients with BN consumed more overall than NC subjects (1200 g vs. 740 g). When instructed to binge in the eating laboratory, patients with BN ate equally large amounts of food at a slow rate as at a fast rate. NC subjects ate less at a slow rate. These findings indicate that in a structured laboratory meal paradigm binge size is not affected by rate of eating.

A disturbance of gastric function in bulimia nervosa.

BACKGROUND: Because the stomach plays an important role in the development of satiety, gastric function was examined in bulimia nervosa (BN). METHODS: Sixteen patients with BN and 16 controls swallowed an inflatable bag, which was positioned in the proximal stomach. Minimal distending pressure (MDP), the pressure needed to overcome intraabdominal pressure, was determined. Gastric volume was recorded after subjects drank a liquid meal. RESULTS: MDP was similar in patient and control groups (7.56 +/- 2.13 vs. 7.13 +/- 2.06 mmHg; t =.57, df = 30, p =.58). Average postmeal gastric relaxation was significantly lower in the patient group (29.7 +/- 97.8 vs. 105.1 +/- 103.3 mL; t = 2.13, df = 30, p =.042). CONCLUSIONS: Stomach relaxation following food consumption is significantly diminished in patients with BN. Physiologic abnormalities of stomach function in BN may contribute to the perpetuation of disturbances in behavior in this disorder.

Development and preliminary validation of a silhouette satiety scale for children.

The purpose of this study was to determine whether young children are capable of using pictorial silhouettes to quantify feelings of satiety and provide preliminary data on the validity of this method. Subjects were 20 children, 4-6 years old, recruited from a preschool. We hypothesized that subjects would be able to use the silhouettes to communicate different levels of satiety when imagining eating situations associated with different levels of fullness. The study was conducted in three stages: Stage 1 probed children's spontaneous definitions of hunger and fullness and identified specific eating situations they associated with these feelings; Stage 2 tested whether children could perform basic quantitative discriminations applied to food-related stimuli; Stage 3 validated the silhouettes using an 'imagined eating situation' in which subjects used the silhouettes to rate how full their belly would feel in three distinct eating situations associated with different levels of satiety. Main results indicated that (1) most children readily associated the stomach with feelings of hunger (90%) and fullness (70%), (2) 80% of the children said they felt fullest after eating a meal, (3) 90-100% of the children were able to perform basic quantitative discriminations using food-related stimuli, and (4) children reported increasing feelings of satiety for situations associated with hunger, partial satiety, and satiety. Children were generally consistent in their ratings across testing sessions, although responses were less consistent for intermediary satiety levels. Young children may be more capable of quantitatively reporting feelings of satiety than is commonly believed, if appropriate experimental materials are used.

Elevated plasma cholecystokinin and appetitive ratings after consumption of a liquid meal in humans.

OBJECTIVE: This study had two objectives. The first was to evaluate the possibility that, in a previous study, a soup preload augmented the reduction of food intake in a test meal induced by an exogenous infusion of cholecystokinin (CCK) because the soup also endogenously released CCK. The second was to compare CCK release by soup between men and women to determine whether the increased satiating effectiveness of soup in women as opposed to men could have been partly attributable to differences in CCK release. METHODS: By using a bioassay that measures all of its known isoforms, we determined plasma CCK levels at baseline and at several times postprandially in eight healthy, non-obese men and women (four of each sex). Each subject ingested 800 g of tomato soup, which was followed 30 min later by 300 g of a yogurt shake. Appetitive ratings were also collected and related to CCK levels. RESULTS: Ingestion of tomato soup significantly increased plasma CCK levels by 3.81 pmol/L (+/- 1.21 standard error, P = 0.016) over baseline within 30 min in all subjects combined. When CCK concentrations at 5 min after soup and 5 min after yogurt were averaged, the women's mean averaged concentration was 5.58 pmol/L (+/- 1.994, t = 2.80, P = 0.0073) higher than the men's. The elevated levels persisted but did not rise further upon consumption of the yogurt shake. Hunger ratings declined and fullness ratings increased after eating, although patterns of ratings did not match exactly patterns of CCK release. CONCLUSIONS: A large quantity of tomato soup stimulates significant CCK release; therefore, some of the satiating effects of soup preloads could have been mediated by an elevation in endogenous CCK.

The evolution of the Society for the Study of Ingestive Behavior (SSIB).

This review summarizes the formation of the Society for the Study of Ingestive Behavior (SSIB), highlighting the many people whose commitment and perseverance brought together a wide range of disciplines for the common goal of investigating ingestive behavior and providing communication via scientific meetings. The goals and philosophy of the Society today are described along with the challenges it will face in the future. It concludes with the important message that excellence in science, combined with commitment to, and participation from, younger investigators, will ensure its continued success. The SSIB was officially incorporated on March 30, 1987 to serve a unique niche within the biological and behavioral sciences. Its initial vision was to serve as the "leading scientific organization for the study of ingestive behavior". This mission continues to drive the philosophy of the Society which currently boasts over 350 members representing 30 different countries. The SSIB melded scientific disciplines that included physiological and psychological aspects of food and fluid intake, as well as taste and olfaction. Prior to its creation, scientists from each of these disciplines met at several key conferences, most notably The International Conference on the Physiology of Food and Fluid Intake, a now defunct satellite of the International Union of Physiological Sciences, and The Eastern Psychological Association. From these and other smaller conferences came the idea of forming a society that integrated research from the biological, psychological and social aspects of food and fluid intake in both animals and humans. While this emphasis of the Society remains today, changing scientific priorities and interests continue to shape and influence the direction of the Society. Since its first meeting held at Princeton University in NJ in 1992, the annual meeting has become a major means of disseminating cutting-edge information on current research in the field of ingestive behavior. The record of its programs provides a valuable window into the workings of what was then a new scientific discipline and its evolution over time which may be useful, not only to members of the SSIB, but also to students of the history of science.

Leptin reverses declines in satiation in weight-reduced obese humans.

BACKGROUND: Individuals who are weight-reduced or leptin deficient have a lower energy expenditure coupled with higher hunger and disinhibition and/or delayed satiation compared with never-weight-reduced control subjects. Because exogenous leptin inhibits feeding in congenitally leptin-deficient humans, reduced leptin signaling may reduce the expression of feeding inhibition in humans. OBJECTIVE: The objective was to test the hypothesis that reduced leptin signaling may reduce the expression of feeding inhibition (ie, blunt satiation) in humans by examining the effects of leptin repletion on feeding behavior after weight loss. DESIGN: Ten obese humans (4 men, 6 women) were studied as inpatients while they received a weight-maintaining liquid-formula diet. Satiation was studied by measuring intake and ratings of appetite-related dispositions 3 h after ingestion of 300 kcal of the liquid-formula diet. The subjects were studied at each of 3 time periods: 1) while they maintained their usual weight (Wt(initial)) and then after weight reduction and stabilization at 10% below initial weight and while they received 5 wk of either 2) twice-daily injections of placebo (Wt(-10%placebo)) or 3) "replacement doses" of leptin (Wt(-10%leptin)) in a single-blind crossover design with a 2-wk washout period between treatments. Energy expenditure was also measured at each study period. RESULTS: Both energy expenditure and visual analog scale ratings that reflect satiation were significantly lower at Wt(-10%placebo) than at Wt(initial) and Wt(-10%leptin). CONCLUSION: The results are consistent with the hypothesis that the absence of leptin signaling after weight loss may blunt the expression of feeding inhibition in humans.

Gastric emptying and symptoms of bulimia nervosa: effect of a prokinetic agent.

OBJECTIVE: Previous studies have suggested that delayed gastric emptying and abnormal postprandial release of hormones that influence satiation, particularly cholecystokinin (CCK), may play an important role in the pathophysiology of bulimia nervosa (BN). This study was designed to test these hypotheses as well as the efficacy of the prokinetic agent erythromycin in patients with BN. METHOD: Thirty-two normal-weight women with BN and 24 control participants consumed a large liquid test meal. Gastric emptying and pre- and postprandial release of CCK, peptide YY (PYY), and ghrelin were determined. Participants with BN were then recruited for double-blind treatment with erythromycin up to 500 mg three times daily vs. placebo for 6 weeks, following which they consumed a repeat test meal with gastric emptying and appetitive hormone measurements. RESULTS: CCK release at 15 min following the meal was marginally lower (p=0.1) in BN than in control participants. Rate of gastric emptying and postprandial hormone release were similar in BN and controls. BN patients assigned to erythromycin compared to those assigned to placebo had more rapid gastric emptying following treatment, but there were no differences in release of CCK, PYY, or ghrelin following the post-treatment test meal. Moreover, treatment with erythromycin was not associated with clinical response. DISCUSSION: The current study does not support the clinical utility of moderate dose erythromycin in treating BN. Furthermore, the findings suggest that a modest increase in gastric emptying rate is associated neither with altered postprandial hormonal release nor with clinical benefit in these patients. While providing no evidence for the effectiveness of prokinetic agents in this setting, our findings do not preclude the possibility that a greater increase in gastric emptying rate might prove beneficial.