Decreased energy density and changes in food selection following Roux-en-Y gastric bypass

Suboptimal Weight Loss and Weight Regain after Gastric Bypass Surgery-Postoperative Status of Energy Intake, Eating Behavior, Physical Activity, and Psychometrics

BACKGROUND

Suboptimal weight loss (SWL) and weight regain (WR) after gastric bypass surgery (GB) remains poorly understood.

OBJECTIVES

This study aims to compare GB patients experiencing SWL or significant WR (SigWR) with successful controls, regarding postoperative food intake, eating behavior, physical activity (PA), and psychometrics.

METHODS

Forty-nine patients with >1 year post-surgery were classified as either experiencing SWL (excess body weight loss, EWL, <50%, n = 22) or SigWR (total weight regain ≥15%, n = 38), with respective control groups. Energy intake (EI) was measured with a Food Frequency Questionnaire, eating behavior using the Dutch Eating Behavior Questionnaire and the Three-Factor Eating Questionnaire, and PA using both SenseWear Armbands and the International Physical Activity Questionnaire. Eating disorders, depression, and quality of life (QoL) were measured using the Eating Disorder Examination Questionnaire, Beck Depression Inventory II, and Impact of Weight on Quality of Life, respectively.

RESULTS

EI, macronutrient distribution, and meal frequency were similar among groups. However, disinhibited eating behavior score was higher, while most subcategories from IWQOL were significantly lower in both SWL and SigWR groups compared with their respective controls. PA was significantly lower in the SWL and SigWR groups compared with the respective controls. There were no differences between groups regarding depression.

CONCLUSIONS

Lower PA levels, disordered eating behavior and lower QoL are associated with unsuccessful weigh loss outcome after GB surgery. Longitudinal studies are needed to clarify the potential causal relationship between the previously described variables and SWL/SigWR after GB.

The Role of GLP-1 in the Metabolic Success of Bariatric Surgery

Two of the most popular bariatric procedures, vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB), are commonly considered metabolic surgeries because they are thought to affect metabolism in a weight loss-independent manner. In support of this classification, improvements in glucose homeostasis, insulin sensitivity, and even discontinuation of type 2 diabetes mellitus (T2DM) medication can occur before substantial postoperative weight loss. The mechanisms that underlie this effect are unknown. However, one of the common findings after VSG and RYGB in both animal models and humans is the sharp postprandial rise in several gut peptides, including the incretin and satiety peptide glucagonlike peptide-1 (GLP-1). The increase in endogenous GLP-1 signaling has been considered a primary pathway leading to postsurgical weight loss and improvements in glucose metabolism. However, the degree to which GLP-1 and other gut peptides are responsible for the metabolic successes after bariatric surgery is continually debated. In this review we discuss the mechanisms underlying the increase in GLP-1 and its potential role in the metabolic improvements after bariatric surgery, including remission of T2DM. Understanding the role of changes in gut peptides, or lack thereof, will be crucial in understanding the critical factors necessary for the metabolic success of bariatric surgery.

Nutritional and Micronutrient Care of Bariatric Surgery Patients: Current Evidence Update

PURPOSE OF REVIEW

The continued success of bariatric surgery to treat obesity and obesity-associated metabolic conditions creates a need for a strong understanding of clinical nutrition both before and after these procedures.

RECENT FINDINGS

Surgically induced alteration of gastrointestinal physiology can affect the nutrition of individuals, especially among those who have undergone malabsorptive procedures. While uncommon, a subset of patients may develop protein-calorie malnutrition. In these cases, nutrition support should be tailored to the severity of malnutrition. Among all patients who undergo bariatric surgery, high rates of micronutrient deficiencies have been observed. To mitigate these deficiencies, empiric supplementation with multivitamins, calcium citrate, and vitamin D is generally recommended. Periodic surveillance should be performed for commonly deficient micronutrients, including thiamin (B1), folate (B9), cobalamin (B12), iron, and vitamin D. Following Roux-en-Y gastric bypass, serum levels of copper and zinc should also be monitored. In addition, lipid-soluble vitamins should be monitored following biliopancreatic diversion with/without duodenal switch.

Absence of Role of Dietary Protein Sensing in the Metabolic Benefits of Duodenal-Jejunal Bypass in the Mouse

Roux-en-Y gastric bypass (RYGB) induces remission or substantial improvement of type 2 diabetes mellitus (T2D) but underlying mechanisms are still unclear. The beneficial effects of dietary proteins on energy and glucose homeostasis are mediated by the antagonist effects of peptides toward mu-opioid receptors (MORs), which are highly expressed in the distal gut. We hypothesized that the beneficial effects of RYGB could depend at least in part on the interaction of peptides from food with intestinal MORs. Duodenal-jejunal bypass (DJB) was performed in obese and lean wild-type (WT) or MOR deficient (MOR^−/−) mice. Food intake and body weight was monitored daily during 3 weeks. Glucose homeostasis was assessed from glucose and insulin tolerance tests. In obese WT and MOR^−/− mice, DJB induced a rapid and sustained weight loss partly independent of food intake, and a rapid improvement in glycaemic parameters. Weight loss was a major determinant of the improvements observed. In lean WT and MOR^−/− mice, DJB had no effect on weight loss but significantly enhanced glucose tolerance. We found that MORs are not essential in the metabolic beneficial effects of DJB, suggesting that protein sensing in the distal gut is not a link in the metabolic benefits of gastric surgery.

Dumping symptoms is triggered by fat as well as carbohydrates in patients operated with Roux-en-Y gastric bypass

BACKGROUND

Dumping syndrome after Roux-en-Y gastric bypass (RYGB) is traditionally associated with the consumption of refined carbohydrates, but the role of dietary fat is unclear.

OBJECTIVES

This study compares symptoms after consumption of a carbohydrate-rich or fat-rich beverage to determine perceived symptoms, glycemic control, and pulse rate.

SETTING

University hospital.

METHODS

We assessed perceived symptoms (Sigstad's Dumping Index) and glycemic control (P-glucose and S-insulin) as well as autonomic nervous system activity (reflected by arterial pulse rate) after a standardized liquid meal test (440 kcal/300 mL carbohydrates [CARB] or fat [FAT]) in a randomized crossover blinded setting. Blood samples were drawn before and 1, 15, 30, and 60 minutes after finishing each meal and the area under the curve (AUC) was calculated.

RESULTS

Twelve patients 42±10 months after undergoing RYGB were studied. AUC differed between drinks for glucose (P = .003) and insulin (P = .005). Pulse rate increased more after CARB than after FAT (P = .01). AUC for perceived symptoms in the Sigstad's Dumping Index were similar after meals (P = .79), yet the pattern of type of symptoms differed.

CONCLUSION

In patients with RYGB, a meal with predominant fat content resulted in as much perceived dumping symptoms as a carbohydrate-profiled meal. As expected, an increase in glucose and insulin levels were found only after carbohydrate intake and the pulse rise was more pronounced for carbohydrates than fat. Dietary counseling in patients undergoing RYGB should address dietary fat as well as traditional information about carbohydrates to avoid dumping symptoms.

Early dumping syndrome is not a complication but a desirable feature of Roux-en-Y gastric bypass surgery

Early dumping syndrome after gastric bypass surgery due to rapid delivery of hyperosmolar nutrients into the bowel causing intense symptoms is often described as a complication. Twelve patients, mean age 47 years, were interviewed approximately 9 years post-operation. The interviews were audiotaped and transcribed verbatim, followed by an inductive content analysis to reveal patients' experience of the dumping syndrome. The core category 'Dumping syndrome is a positive consequence of Roux-en-Y gastric bypass surgery and a tool to control food intake' was identified based on the following four sub-categories: (i) 'The multidimensional emergence and effects of dumping syndrome', (ii) 'Dumping syndrome as something positive although unpleasant', (iii) 'Developing coping mechanisms and ingenious strategies' and (iv) 'My own fault if I expose myself to dumping syndrome'. From the patients' perspective, dumping syndrome gives control over food intake; although the symptoms were unpleasant, patients considered dumping syndrome as a positive protection against over-consumption. Hence, healthcare professionals should not present dumping syndrome as a complication but rather as an aid to control eating behaviour and excessive food intake.

Body Composition, Food Intake, and Energy Expenditure in a Murine Model of Roux-en-Y Gastric Bypass Surgery

BACKGROUND

The mechanisms by which Roux-en-Y gastric bypass surgery (RYGB) so effectively lowers body weight and improves glycemic control are not well understood, and murine models are essential for identifying the crucial signaling pathways involved. The aim of this study is to characterize the time course of RYGB on body weight, body composition, food intake, and energy expenditure in diet-induced obese mice and establish a tissue bank for global "omics" or targeted biochemical and structural analyses.

METHODS

High-fat diet-induced obese mice were subjected to RYGB using an improved surgical technique with a small gastric pouch. The effects on body weight, body composition, food intake, and energy expenditure were compared to sham surgery, high-fat diet-restricted weight-matched controls, and never-obese chow-fed controls.

RESULTS

Without mortality or complications, RYGB surgery in high-fat diet-induced obese mice gradually decreased body weight to a plateau that was more or less sustained for up to 12 weeks (33 g, -18 %, p < 0.01) and significantly lower compared with sham-operated mice (51 g, +25 %, p < 0.01), but higher (+18 %, p < 0.01) than age-matched, chow-fed control mice (27 g). Energy intake after RYGB was significantly suppressed compared to sham only for the first 10 days, but significantly higher compared to weight-matched mice. Energy expenditure after RYGB was higher throughout the study compared with weight-matched, but not sham animals.

CONCLUSIONS

RYGB surgery in diet-induced obese mice results in similar body weight and body composition changes as observed in humans, but in contrast with humans, this is achieved mainly through increased energy expenditure rather than decreased food intake.

How do patients' clinical phenotype and the physiological mechanisms of the operations impact the choice of bariatric procedure?

Bariatric surgery is currently the most effective option for the treatment of morbid obesity and its associated comorbidities. Recent clinical and experimental findings have challenged the role of mechanical restriction and caloric malabsorption as the main mechanisms for weight loss and health benefits. Instead, other mechanisms including increased levels of satiety gut hormones, altered gut microbiota, changes in bile acid metabolism, and/or energy expenditure have been proposed as explanations for benefits of bariatric surgery. Beside the standard proximal Roux-en-Y gastric bypass and the biliopancreatic diversion with or without duodenal switch, where parts of the small intestine are excluded from contact with nutrients, resectional techniques like the sleeve gastrectomy (SG) have recently been added to the armory of bariatric surgeons. The variation of weight loss and glycemic control is vast between but also within different bariatric operations. We surveyed members of the Swiss Society for the Study of Morbid Obesity and Metabolic Disorders to assess the extent to which the phenotype of patients influences the choice of bariatric procedure. Swiss bariatric surgeons preferred Roux-en-Y gastric bypass and SG for patients with type 2 diabetes mellitus and patients with a body mass index >50 kg/m², which is consistent with the literature. An SG was preferred in patients with a high anesthetic risk or previous laparotomy. The surgeons’ own experience was a major determinant as there is little evidence in the literature for this approach. Although trends will come and go, evidence-based medicine requires a rigorous examination of the proof to inform clinical practice.

Reconfiguration of the small intestine and diabetes remitting effects of Roux-en-Y gastric bypass surgery

PURPOSE OF REVIEW

Alterations in small intestinal physiology are proposed to play a causative role in the beneficial impact of Roux-en-Y gastric bypass on type 2 diabetes mellitus. The present article describes the key proposed mechanisms implicated with an emphasis on some of the newer findings in the field.

RECENT FINDINGS

Augmented incretin and diminished anti-incretin effects postsurgery are explored and a model proposed that reconciles the hindgut and foregut hypotheses of improved glycaemic control as being complementary rather than mutually exclusive. Synthesis of recent findings on postbypass changes in intestinal glucose handling then follows. Finally an updated view of the role of distal bile diversion and changes in the microbiota on enteroendocrine signalling is presented.

SUMMARY

A series of nonmutually exclusive changes in small intestinal physiology likely make a significant contribution to improved glycaemic control postgastric bypass. Longitudinal data indicate that these effects do not translate into a long-term cure. A number of surgery-induced changes, however, are amenable to device-based and pharmacology-based mimicry, and this is an area for prioritization of future research focus.

Centrally Administered Ghrelin Acutely Influences Food Choice in Rodents

We sought to determine whether the orexigenic hormone, ghrelin, is involved in the intrinsic regulation of food choice in rats. Ghrelin would seem suited to serve such a role given that it signals hunger information from the stomach to brain areas important for feeding control, including the hypothalamus and reward system (e.g. ventral tegmental area, VTA). Thus, in rats offered a choice of palatable foods (sucrose pellets and lard) superimposed on regular chow for 2 weeks, we explored whether acute central delivery of ghrelin (intracerebroventricular (ICV) or intra-VTA) is able to redirect their dietary choice. The major unexpected finding is that, in rats with high baseline lard intake, acute ICV ghrelin injection increased their chow intake over 3-fold, relative to vehicle-injected controls, measured at both 3 hr and 6 hr after injection. Similar effects were observed when ghrelin was delivered to the VTA, thereby identifying the VTA as a likely contributing neurobiological substrate for these effects. We also explored food choice after an overnight fast, when endogenous ghrelin levels are elevated, and found similar effects of dietary choice to those described for ghrelin. These effects of fasting on food choice were suppressed in models of suppressed ghrelin signaling (i.e. peripheral injection of a ghrelin receptor antagonist to rats and ghrelin receptor (GHSR) knock-out mice), implicating a role for endogenous ghrelin in the changes in food choice that occur after an overnight fast. Thus, in line with its role as a gut-brain hunger hormone, ghrelin appears to be able to acutely alter food choice, with notable effects to promote "healthy" chow intake, and identify the VTA as a likely contributing neurobiological substrate for these effects.

Mechanism Underlying the Weight Loss and Complications of Roux-en-Y Gastric Bypass. Review

Various bariatric surgical procedures are effective at improving health in patients with obesity associated co-morbidities, but the aim of this review is to specifically describe the mechanisms through which Roux-en-Y gastric bypass (RYGB) surgery enables weight loss for obese patients using observations from both human and animal studies. Perhaps most but not all clinicians would agree that the beneficial effects outweigh the harm of RYGB; however, the mechanisms for both the beneficial and deleterious (for example postprandial hypoglycaemia, vitamin deficiency and bone loss) effects are ill understood. The exaggerated release of the satiety gut hormones, such as GLP-1 and PYY, with their central and peripheral effects on food intake has given new insight into the physiological changes that happen after surgery. The initial enthusiasm after the discovery of the role of the gut hormones following RYGB may need to be tempered as the magnitude of the effects of these hormonal responses on weight loss may have been overestimated. The physiological changes after RYGB are unlikely to be due to a single hormone, or single mechanism, but most likely involve complex gut-brain signalling. Understanding the mechanisms involved with the beneficial and deleterious effects of RYGB will speed up the development of effective, cheaper and safer surgical and non-surgical treatments for obesity.

Striatal Dopamine Links Gastrointestinal Rerouting to Altered Sweet Appetite

Reductions in calorie intake contribute significantly to the positive outcome of bariatric surgeries. However, the physiological mechanisms linking the rerouting of the gastrointestinal tract to reductions in sugar cravings remain uncertain. We show that a duodenal-jejunal bypass (DJB) intervention inhibits maladaptive sweet appetite by acting on dopamine-responsive striatal circuitries. DJB disrupted the ability of recurrent sugar exposure to promote sweet appetite in sated animals, thereby revealing a link between recurrent duodenal sugar influx and maladaptive sweet intake. Unlike ingestion of a low-calorie sweetener, ingestion of sugar was associated with significant dopamine effluxes in the dorsal striatum, with glucose infusions into the duodenum inducing greater striatal dopamine release than equivalent jejunal infusions. Consistently, optogenetic activation of dopamine-excitable cells of the dorsal striatum was sufficient to restore maladaptive sweet appetite in sated DJB mice. Our findings point to a causal link between striatal dopamine signaling and the outcomes of bariatric interventions.

Great Health Benefits But No Change in Employment or Psychopharmaceutical Drug Use 2 Years After Roux-en-Y Gastric Bypass

BACKGROUND

The aim was to examine health benefits and lifestyle factors after Roux-en-Y gastric bypass (RYGB).

METHODS

Patients (n = 165) were investigated 2 years after RYGB in relation to psychopharmaceutical drugs, employment status, type 2 diabetes mellitus (T2DM), hypertension, metabolic syndrome (MetS), body weight, physical activity (PA), and energy intake.

RESULTS

Excess weight loss (EWL) was 71.4 ± 20.6 %. Prevalence of T2DM, hypertension, and MetS was reduced (P < 0.001 for all). There were no changes in the use of psychopharmaceutical drugs (20.6 vs. 18.8 %, P = 0.549) or in the proportion of unemployed participants (37.7 vs. 33.3 %, P = 0.189) from pre- to post-surgery. Eighty-three percent achieved EWL ≥ 50 %. These subjects had a lower pre-surgery BMI. We found no differences in the prevalence of hypertension, T2DM, and MetS pre-surgery, but the prevalence was lower after surgery compared with subjects with EWL < 50 %.

CONCLUSION

RYGB induced remission of T2DM, hypertension, and MetS 2 years after surgery. The benefit was greatest in the group with EWL ≥ 50 %. Despite excellent weight loss, there was no change in the use of psychopharmaceutical drugs or proportion of unemployed participants.

Changes in eating behaviour and food choices in families where the mother undergoes gastric bypass surgery for obesity

BACKGROUND/OBJECTIVES

There is a lack of research exploring the effects of Roux-en-Y gastric bypass (RYGB) surgery on the patient's family's eating behaviour and food choices. The aim of the current study was to investigate changes in partners' and children's eating behaviour and food choices following maternal RYGB.

SUBJECTS/METHODS

Sixty-nine women and their families were recruited from RYGB waiting lists at five Swedish surgical clinics. Data were collected during home visits 3 months before and 9 months after RYGB. Anthropometrical measures were taken, the adults completed the Three-Factor Eating Questionnaire and the children completed the Children's Eating Attitudes Test (ChEAT). All participants also completed a short food frequency questionnaire.

RESULTS

Changes in scores were analysed using paired t-tests for unadjusted estimates or linear regression models with robust variance (General Estimating Equations) in order to enable age- and sex-adjusted estimates for the children. There were no meaningful differences in the partners' eating behaviour or food choices. The boys, but not the girls, improved their ChEAT scores, as did the overweight/obese children in comparison with the normal-weight children. The boys, unlike the girls, also decreased their intake of soft drinks, as did the normal-weight children when compared with the overweight/obese children.

CONCLUSIONS

No clear-cut changes were found in partners' eating behaviour and food choices. Eating attitudes and soft drinks intake were improved among boys but not among girls. Differing modelling behaviour may partially explain these findings, but available data did not allow us to understand the underlying mechanisms.

Reduced sweet and fatty fluid intake after Roux-en-Y gastric bypass in rats is dependent on experience without change in stimulus motivational potency

Here we assessed how intake reductions induced by Roux-en-Y gastric bypass surgery (RYGB) occur within and across access periods by examining drinking microstructure. After training, RYGB (n = 8-10) or sham-operated (SHAM, n = 12) rats were given 60-min access first to 0.3 M sucrose, then to 5% Intralipid, and finally to milk-chocolate Ensure Plus across 5 days each. Initially, total licks taken during the first meal of sucrose and Intralipid by RYGB and SHAM rats did not differ, but, across subsequent test periods, RYGB rats licked less than SHAM rats. First Ensure meal size also did not differ between RYGB and SHAM rats, but SHAM rats increased licking across test periods while the behavior of RYGB rats remained stable. The intake differences between the surgical groups, when they occurred, were most often due to smaller burst sizes in RYGB rats. Importantly, the surgical-group difference in sucrose and Intralipid intakes could not be explained by altered palatability of these solutions because, throughout testing, both groups had similar early meal licking behavior thought to represent the motivational potency of stimulus orosensory features. Although, overall, RYGB rats displayed lower early meal licking of Ensure relative to the SHAM rats, this appeared to be driven primarily by increases in the latter group across test periods; the RYGB group stayed relatively stable. Collectively, these results suggest that some level of postoral experience with these stimuli and/or their components is necessary before intake differences emerge between surgical groups, and, even when differences occur, often immediate taste-motivated ingestive behavior remains unaltered.

[Dumping syndrome: Diagnostics and therapeutic options]

BACKGROUND

Dumping syndrome is a common complication after surgery of the upper gastrointestinal tract with symptoms ranging from mild gastrointestinal discomfort and moderate vasomotor disturbances, to severe hyperinsulinemic hypoglycemia. Due to the increasing number of bariatric procedures being performed worldwide, bariatric surgery has become the most common cause for this disease entity.

OBJECTIVE

The aim of this review is to highlight the evidence for the physiological mechanisms contributing to dumping syndrome after the two most common bariatric surgery procedures, Roux-en-Y gastric bypass and sleeve gastrectomy, to discuss technical aspects of the procedures underlying the development of the syndrome, patient-related predictive factors and other differential diagnoses, together with diagnostic and therapeutic algorithms.

Food preferences and underlying mechanisms after bariatric surgery

Bariatric surgery leads to significant long-term weight loss, particularly Roux-en-Y gastric bypass (RYGB). The mechanisms underlying weight loss have not been fully uncovered. The aim of this review is to explore the changes in food preferences, as a novel mechanism contributing to weight loss, and also focus on the underlying processes modulating eating behaviour after bariatric surgery. Patients after gastric bypass are less hungry and prefer healthier food options. They develop an increased acuity to sweet taste, which is perceived as more intense. The appeal of sweet fatty food decreases, with functional MRI studies showing a corresponding reduction in activation of the brain reward centres to high-energy food cues. Patients experiencing post-ingestive symptoms with sweet and fatty food develop conditioned aversive behaviours towards the triggers. Gut hormones are elevated in RYGB and have the potential to influence the taste system and food hedonics. Current evidence supports a beneficial switch in food preferences after RYGB. Changes within the sensory and reward domain of taste and the development of post-ingestive symptoms appear to be implicated. Gut hormones may be the mediators of these alterations and therefore exploiting this property might prove beneficial for designing future obesity treatment.

Gastric bypass in rats does not decrease appetitive behavior towards sweet or fatty fluids despite blunting preferential intake of sugar and fat

After Roux-en-Y gastric bypass surgery (RYGB), patients report consuming fewer fatty and dessert-like foods, and rats display blunted sugar and fat preferences. Here we used a progressive ratio task (PR) in our rat model to explicitly test whether RYGB decreases the willingness of rats to work for very small amounts of preferred sugar- and/or fat-containing fluids. In each of two studies, two groups of rats - one maintained on a high-fat diet (HFD) and standard chow (CHOW) and one given CHOW alone - were trained while water-deprived to work for water or either Ensure or 1.0 M sucrose on increasingly difficult operant schedules. When tested before surgery while nondeprived, HFD rats had lower PR breakpoints (number of operant responses in the last reinforced ratio) for sucrose, but not for Ensure, than CHOW rats. After surgery, at no time did rats given RYGB show lower breakpoints than SHAM rats for Ensure, sucrose, or when 5% Intralipid served postoperatively as the reinforcer. Nevertheless, RYGB rats showed blunted preferences for these caloric fluids versus water in 2-bottle preference tests. Importantly, although the Intralipid and sucrose preferences of RYGB rats decreased further over time, subsequent breakpoints for them were not significantly impacted. Collectively, these data suggest that the observed lower preferences for normally palatable fluids after RYGB in rats may reflect a learned adjustment to altered postingestive feedback rather than a dampening of the reinforcing taste characteristics of such stimuli as measured by the PR task in which postingestive stimulation is negligible.

Appetite and body weight regulation after bariatric surgery

Bariatric surgery continues to be remarkably efficient in treating obesity and type 2 diabetes mellitus and a debate has started whether it should remain the last resort only or also be used for the prevention of metabolic diseases. Intense research efforts in humans and rodent models are underway to identify the critical mechanisms underlying the beneficial effects with a view towards non-surgical treatment options. This non-systematic review summarizes and interprets some of this literature, with an emphasis on changes in the controls of appetite. Contrary to earlier views, surgery-induced reduction of energy intake and subsequent weight loss appear to be the main drivers for rapid improvements of glycaemic control. The mechanisms responsible for suppression of appetite, particularly in the face of the large weight loss, are not well understood. Although a number of changes in food choice, taste functions, hedonic evaluation, motivation and self-control have been documented in both humans and rodents after surgery, their importance and relative contribution to diminished appetite has not yet been demonstrated. Furthermore, none of the major candidate mechanisms postulated in mediating surgery-induced changes from the gut and other organs to the brain, such as gut hormones and sensory neuronal pathways, have been confirmed yet. Future research efforts should focus on interventional rather than descriptive approaches in both humans and rodent models.

The threshold shift paradigm of obesity: evidence from surgically induced weight loss

BACKGROUND

The high prevalence of obesity has called attention to the near-intractable problem of sustained weight reduction and its underlying mechanisms. With diet-induced weight loss, achieved body weight is closely related to initial body weight.

OBJECTIVE

The objective was to compare the relation between initial and achieved body mass index (BMI) in patients treated with diet-induced weight loss or bariatric surgery.

DESIGN

We analyzed data from a cohort of 223 healthy individuals who lost a mean (±SD) of 5 ± 3 kg body weight over 3 y by diet (diet group) and data from 182 obese individuals [BMI (in kg/m(2)) ≥35] who had lost an average of 47 ± 17 kg 1 y after Roux-en-Y gastric bypass (a restrictive procedure; n = 71) or biliopancreatic diversion (a malabsorptive procedure; n = 111) (surgery group).

RESULTS

In the diet group, final BMI was strongly related to initial BMI (r = 0.96, P < 0.0001). By multivariate analysis, the decrease in BMI at 3 y was age independent and was predicted only by initial BMI and sex (both P < 0.0001). Strikingly, final BMI was also strongly related to initial BMI (r = 0.67, P < 0.0001) in the surgery group, irrespective of the type of operation. The surgically induced decrease in BMI was predicted by age (P = 0.0002) and initial BMI (P < 0.0001). In 110 surgery patients, serum leptin concentrations decreased from 39 ± 16 to 10 ± 5 ng/mL after surgery (P < 0.0001) and were correlated with BMI both before and after surgery, but the slope of the relation was significantly (P < 0.01) flatter after surgery.

CONCLUSION

The strong predictivity of initial BMI for achieved BMI observed even when voluntary control of energy intake is interfered with through diverse anatomical rearrangements of the gastrointestinal tract supports the concept of a weight "threshold" paradigm: in the obese, anabolic responses are triggered by adiposity-related signals at a higher threshold, which leads to defense of a higher body weight.

The neuropathology of obesity: insights from human disease

Obesity, a pathologic state defined by excess adipose tissue, is a significant public health problem as it affects a large proportion of individuals and is linked with increased risk for numerous chronic diseases. Obesity is the result of fundamental changes associated with modern society including overnutrition and sedentary lifestyles. Proper energy homeostasis is dependent on normal brain function as the master metabolic regulator, which integrates peripheral signals, modulates autonomic outflow and controls feeding behavior. Therefore, many human brain diseases are associated with obesity. This review explores the neuropathology of obesity by examining brain diseases which either cause or are influenced by obesity. First, several genetic and acquired brain diseases are discussed as a means to understand the central regulation of peripheral metabolism. These diseases range from monogenetic causes of obesity (leptin deficiency, MC4R deficiency, Bardet-Biedl syndrome and others) to complex neurodevelopmental disorders (Prader-Willi syndrome and Sim1 deficiency) and neurodegenerative conditions (frontotemporal dementia and Gourmand's syndrome) and serve to highlight the central regulatory mechanisms which have evolved to maintain energy homeostasis. Next, to examine the effect of obesity on the brain, chronic neuropathologic conditions (epilepsy, multiple sclerosis and Alzheimer's disease) are discussed as examples of obesity leading to maladaptive processes which exacerbate chronic disease. Thus, obesity is associated with multiple pathways including abnormal metabolism, altered hormonal signaling and increased inflammation which act in concert to promote downstream neuropathology. Finally, the effect of anti-obesity interventions is discussed in terms of brain structure and function. Together, understanding human diseases and anti-obesity interventions leads to insights into the bidirectional interaction between peripheral metabolism and central brain function, highlighting the need for continued clinicopathologic and mechanistic studies of the neuropathology of obesity.