Effects of RYGB on energy expenditure, appetite and glycaemic control: a randomized controlled clinical trial.

OBJECTIVES: Increased energy expenditure (EE) has been proposed as an important mechanism for weight loss following Roux-en-Y gastric bypass (RYGB). However, this has never been investigated in a controlled setting independent of changes in energy balance. Similarly, only few studies have investigated the effect of RYGB on glycaemic control per se. Here, we investigated the effect of RYGB on EE, appetite, glycaemic control and specific signalling molecules compared with a control group in comparable negative energy balance. SUBJECTS/METHODS: Obese normal glucose-tolerant participants were randomized to receive RYGB after 8 (n=14) or 12 weeks (n=14). The protocol included a visit at week 0 and three visits (weeks 7, 11 and 78) where 24-h EE, appetite and blood parameters were assessed. Participants followed a low-calorie diet from weeks 0-11, with those operated at week 12 serving as a control group for those operated at week 8. RESULTS: Compared with controls, RYGB-operated participants had lower body composition-adjusted 24-h EE and basal EE 3 weeks postoperatively (both P<0.05) but EE parameters at week 78 were not different from preoperative values (week 7). Surgery changed the postprandial response of glucagon-like peptide-1 (GLP-1), peptide YY3-36 (PYY), ghrelin, cholecystokinin, fibroblast growth factor-19 and bile acids (all P<0.05). Particularly, increases in GLP-1, PYY and decreases in ghrelin were associated with decreased appetite. None of HOMA-IR (homeostasis model assessment-estimated insulin resistance), Matsuda index, the insulinogenic index, the disposition index and fasting hepatic insulin clearance were different between the groups, but RYGB operated had lower fasting glucose (P<0.05) and the postprandial glucose profile was shifted to the left (P<0.01). CONCLUSIONS: Our data do not support that EE is increased after RYGB. More likely, RYGB promotes weight loss by reducing appetite, partly mediated by changes in gastrointestinal hormone secretion. Furthermore, we found that the early changes in glycaemic control after RYGB is to a large extent mediated by caloric restriction.

The role of hormonal factors in weight loss and recidivism after bariatric surgery.

Substantial heterogeneity exists in weight loss trajectories amongst patients following bariatric surgery. Hormonal factors are postulated to be amongst the contributors to the variation seen. Several hormones involved in hunger, satiety, and energy balance are affected by bariatric surgery, with the alteration in hormonal milieu varying by procedure. Limited research has been conducted to examine potential hormonal mediators of weight loss failure or recidivism following bariatric surgery. While hormonal factors that influence weight loss success following gastric banding have not been identified, data suggest that hormonal factors may be involved in modulating weight loss success following gastric bypass. There may be hormonal mediators involved in determining the weight trajectory following sleeve gastrectomy, though the extremely limited data currently available prohibits definitive conclusions from being drawn. There is great need for future research studies to explore this knowledge gap, as improving this knowledge base could be of benefit to guide clinicians toward understanding the hormonal contributors to a patient's postoperative weight loss failure or recidivism or perhaps be of value in selecting the most appropriate bariatric procedure based on the preoperative hormone milieu. Integrative interdisciplinary approaches exploring these complex interrelationships could potentially increase the explanatory power of such investigations.

Reduction of misclassification rates of obesity by body mass index using dual-energy X-ray absorptiometry scans to improve subsequent prediction of per cent fat mass in a Caucasian population.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: • Body mass index (BMI) is not accurate in the classification of excess body fat, failing to identify as many as half of individuals with excess per cent fat mass. • Normal-weight obesity, which goes undiagnosed when BMI is the only measure of adiposity utilized, has been shown to be associated with an increased risk of cardiovascular comorbidities and mortality. • Dual-energy X-ray absorptiometry (DXA) is an accurate and relatively inexpensive method for indirect assessment of body composition. WHAT THIS STUDY ADDS: • The formulae developed allow the clinician to utilize information from one baseline DXA scan to calculate a patient's per cent fat mass with a future change in weight, thus allowing the clinician to more accurately determine whether and when an individual patient should be classified as obese and thus be managed appropriately. • The formulae developed enable the clinician to calculate a patient-specific BMI treatment goal, below which the patient would no longer meet the per cent fat mass criteria for obesity. SUMMARY: Recognition is increasing for the errors of body mass index (BMI) in classification of excess body fat. Dual-energy X-ray absorptiometry (DXA) is accurate to assess body fat mass per cent (%FM), but is underutilized clinically. We examined the prevalence of obesity misclassification by BMI in comparison to body %FM by DXA scanning, and whether there is a time-stable individual relation between the %FM and the BMI in patients scanned several times. We aimed to develop a formula where, based on a single DXA scan, %FM could be predicted following a change in weight, and a patient-specific BMI threshold could be calculated (BMIT ), above which the patient would be obese by %FM criteria. Data were collected from individuals who had a DXA scan as part of a nutritional research study at the University of Copenhagen. BMI incorrectly classified 48/329 (14.6%) of men and 52/589 (8.8%) of women. The majority of men with BMI 25-27 kg m(-2) and women with BMI 24-26 kg m(-2) were misclassified. Using multiple scan data (189 men, 311 women) and calculating the patient-specific constant C = (1 - %FM/100)(3/2) × BMI from baseline BMI and %FM, misclassification rates were halved for both genders when a personal threshold, BMIT , was used ([BMIT = C/(0.75)(3/2) ] for men and [BMIT = C/(0.65)(3/2) ] for women). We conclude that simple formulae allow evaluation of fatness of individual patients more accurately than BMI, with the use of one baseline DXA scan, and enable the establishment of patient-specific obesity treatment targets in clinical practice.

Errors in patient perception of caloric deficit required for weight loss--observations from the Diet Plate Trial.

Persons with obesity may be poor estimators of caloric content of food. Health care professionals encourage patients to consult nutritional labels as one strategy to assess and restrict caloric intake. Among subjects enrolled in a weight loss clinical trial, the objective is to determine the accuracy of subjects' estimates of caloric deficit needed to achieve the desired weight loss. A 6-month controlled trial demonstrated efficacy of a portion control tool to induce weight loss in 130 obese people with type 2 diabetes. All subjects had previously received dietary teaching from a dietician and a nurse. At baseline, patients were asked how much weight they would like to lose and to quantitatively estimate the caloric deficit required to achieve this weight loss. The stated amount of weight loss desired ranged from 4.5 to 73 kg, with an average of 26.6 kg (n = 127 respondents). Only 30% of participants were willing to estimate the required caloric deficit to lose their target weight. Subjects' per kilograms estimate of caloric deficit required ranged from 0.7 to 2,000,000 calories/kg with a median of 86 calories/kg. Nearly half of subjects (47.4%) underestimated the total required caloric deficit to achieve their target weight loss by greater than 100,000 calories. Despite attendance at a diabetes education centre, this population of obese individuals had a poor understanding of the quantitative relationship between caloric deficit and weight loss. Educational initiatives focused upon quantitative caloric intake and its impact on weight change may be needed to assist obese patients in setting appropriate weight loss goals and achieving the appropriate daily caloric restriction required for success.

Stress levels experienced by the parents of enterally fed children.

BACKGROUND: The stress levels of parents of children with chronic illness/disability who were also involved in an enteral feeding programme were examined and compared to the stress levels of parents of healthy children and parents of children with other chronic illnesses reported in previous research. METHODS: Sixty-four parents who had a child with an enteral feeding tube completed the Parenting Stress Index (PSI). RESULTS: Based on criteria developed by Abidin (1995), 42.18% (n = 29) of these parents displayed high stress levels. T-tests revealed that Total Stress scores on the PSI of the parents of children involved in the enteral feeding programme were significantly higher than those reported in the sample of parents used to norm the PSI (P < 0.001), and comparison samples of parents of children with growth deficiencies (P < 0.001) and parents of children with insulin-dependent diabetes mellitus (P < 0.01). Compared to a sample of parents of children with Rett syndrome, the parents of children involved in the enteral feeding programme reported similar levels of stress on the Parent Domain of the PSI and significantly less stress on the Child Domain (P < 0.001). CONCLUSIONS: Factors associated with the stress reported by parents of children with an enteral feeding tube were severity of their child's illness/disability, the constant caretaking demands placed on the parent, and the level of support provided by the parents' social network.