Ongoing Inconsistencies in Weight Loss Reporting Following Bariatric Surgery: a Systematic Review

Evaluation of the impact of gastric bypass surgery on eating behaviour using objective methodologies under residential conditions: Rationale and study protocol

Gastric bypass surgery leads to significant and sustained weight loss and a reduction in associated health risks in individuals with severe obesity. While reduced energy intake (EI) is the primary driver of weight loss following surgery, the underlying mechanisms accounting for this energy deficit are not well understood. The evidence base has been constrained by a lack of fit-for-purpose methodology in assessing food intake coupled with follow-up studies that are relatively short-term. This paper describes the underlying rationale and protocol for an observational, fully residential study using covert, objective methodology to evaluate changes in 24-hr food intake in patients (n = 31) at 1-month pre-surgery and 3-, 12- and 24-months post-surgery, compared to weight-stable controls (n = 32). The main study endpoints included change in EI, macronutrient intake, food preferences, and eating behaviours (speed, frequency, and duration of eating). Other physiological changes that may influence EI and weight regulation including changes in body composition, circulating appetite hormones, resting metabolic rate, total energy expenditure and gastrointestinal symptoms were also evaluated. Understanding which mechanisms contribute to a reduction in EI and weight loss post-surgery could potentially help to identify those individuals who are most likely to benefit from gastric bypass surgery as well as those that may need more targeted intervention to optimise their weight loss post-surgery. Furthermore, clarification of these mechanisms may also inform targeted approaches for non-surgical treatments of obesity.

Place Work on a Scale: What Do We Know About the Association Between Employment Status and Weight Loss Outcomes After Bariatric Surgery?

Despite the initial successful weight loss after bariatric surgery, a significant amount of patients experience weight loss failure and weight regain. Several factors are known to contribute to this, though the impact of employment status is unknown. The objective of this systematic review was to examine the impact of employment status on post-surgical weight loss outcomes. Eight studies were included with a follow-up ranging between 2 and 10 years. Employed patients seemed to present more weight loss (9.0-11.0% EWL, 1.3-1.6% BMI loss) compared to unemployed patients, but none of these numbers were statistically significant. Moreover, there were contrasting findings in terms of weight regain. This review may highlight the importance of working status after bariatric surgery and warrants further investigation on this topic.

Methodological issues in assessing change in dietary intake and appetite following gastric bypass surgery: A systematic review

Gastric bypass surgery is an effective long-term treatment for individuals with severe obesity. Changes in appetite, dietary intake, and food preferences have all been postulated to contribute to postoperative body weight regulation, however, findings are inconsistent. The aim of this systematic review was to evaluate the current literature on changes in dietary intake and appetite following gastric bypass surgery, in the context of the methodology used and the analysis, interpretation, and presentation of results. Four databases were systematically searched with terms related to "gastric bypass surgery," "appetite," and "dietary intake," and 49 papers (n = 2384 patients after gastric bypass) were eligible for inclusion. The evidence indicated that only a reduction in overall energy intake and an increase in postprandial satiety are maintained beyond 6-month post-surgery, whereas relative macronutrient intake and premeal hunger remain unchanged. However, available data were limited by inconsistencies in the methods, analysis, presentation, and interpretation of results. In particular, there was a reliance on data collected by subjective methods with minimal acknowledgment of the limitations, such as misreporting of food intake. There is a need for further work employing objective measurement of appetite and dietary intake following gastric bypass surgery to determine how these mechanisms may contribute to weight regulation in the longer term.

Primary and Secondary Nonresponse Following Bariatric Surgery: a Survey Study in Current Bariatric Practice in the Netherlands and Belgium

PURPOSE

Primary nonresponse (1NR) - inability to achieve adequate weight loss after surgery - and secondary nonresponse (2NR) - excessive weight regain after initial adequate weight loss after surgery - can occur in up to 25-35% of patients after bariatric surgery. The aim of this study was to explore the variations in both definition as well as management of 1NR and 2NR amongst bariatric surgeons.

MATERIALS AND METHODS

An online survey was distributed to all members of the national bariatric societies in the Netherlands and Belgium regarding questions about definition, work-up and treatment of 1NR and 2NR after bariatric surgery.

RESULTS

A total of 45 responses from bariatric surgeons were obtained, representing 32 medical centers that perform bariatric procedures. When assessing 1NR, excess weight loss(EWL) was reported to be used by most respondents(30/45), total body weight loss(TBWL) by 18/45 and body mass index(BMI) by 25/45. A great variation in cut off values was observed. When assessing 2NR, percentage weight gain from the lowest (nadir) weight was preferred most by 22/45 respondents with cut off values varying from 5 to 20%. Most respondents deemed 18 months after initial surgery the most appropriate timeframe to determine 1NR or 2NR.

CONCLUSIONS

The current practice regarding primary and secondary nonresponse after bariatric surgery has a wide variety in definitions, work-up and treatment options. Consensus on the definition of 1NR and 2NR is needed to optimize the treatment of bariatric patients.

Standardized reporting of co-morbidity outcome after bariatric surgery: low compliance with the ASMBS outcome reporting standards despite ease of use

BACKGROUND

Despite the publication of the American Society for Metabolic and Bariatric Surgery (ASMBS) Outcome Reporting Standards in 2015, there is still a great variety in definitions used for reporting remission of co-morbidities after bariatric surgery. This hampers meaningful comparison of results.

OBJECTIVE

To assess compliance with the ASMBS standards in current literature, and to evaluate use of the standards by applying them in a report on the outcomes of 5 co-morbidities after bariatric surgery.

SETTING

Two clinics of the Dutch Obesity Clinic, location Den Haag and Velp, and three affiliated hospitals: Haaglanden Medical Center in Den Haag, Groene Hart Hospital in Gouda, and Vitalys Clinic in Velp.

METHODS

A systematic search in PubMed was conducted to identify studies using the ASMBS standards. Besides, the standards were applied to a cohort of patients who underwent a primary bariatric procedure between November 2016 and June 2017. Outcomes of co-morbidities were determined at 6 and 12 months after surgery.

RESULTS

Ten previous studies applying ASMBS definitions were identified by the search, including 6 studies using portions of the definitions, and 4 using complete definitions for 3 co-morbidities or in a small population. In this study, the standards were applied to 1064 patients, of whom 796 patients (75%) underwent Roux-en-Y gastric bypass and 268 patients (25%) underwent sleeve gastrectomy. At 12 months, complete remission of diabetes (glycosylated hemoglobin <6%, off medication) was reached in 63%, partial remission (glycosylated hemoglobin 6%-6.4%, off medication) in 7%, and improvement in 28% of patients (n = 232/248, 94%). Complete remission of hypertension (normotensive, off medication) was noted in 8%, partial remission (prehypertensive, off medication) in 23% and improvement in 63% (n = 397/412, 96%). Remission rate for dyslipidemia (normal nonhigh-density lipoprotein, off medication) was 57% and improvement rate was 19% (n = 129/133, 97%). Resolution of gastroesophageal reflux disease (no symptoms, off medication) was observed in 54% (n = 265/265). Obstructive sleep apnea syndrome improved in 90% (n = 157/169, 93%).

CONCLUSIONS

Compliance with the ASMBS standards is low, despite ease of use. Standardized definitions provided by the ASMBS guideline could be used in future research to enable comparison of outcomes of different studies and surgical procedures.

Metabolic Impact of Body Fat Percentage Independent of Body Mass Index in Women with Obesity Remission After Gastric Bypass

BACKGROUND/OBJECTIVE

Body mass index (BMI) is central when evaluating treatment effect after gastric bypass. The metabolic impact of BMI-independent differences in body fat percentage (BF%) after gastric bypass is not fully understood. We compared metabolic and adipose tissue characteristics in women with high versus low BF% independent of BMI after obesity remission following gastric bypass.

SUBJECTS/METHODS

A cohort of 215 women was included at baseline. A total of 166 women were re-examined 2 years after gastric bypass, whereof 130 had obesity remission (BMI < 30 kg/m2). Anthropometric parameters, blood pressure, and lipids were measured. Total and regional body fat mass was determined by dual-energy X-ray absorptiometry. Insulin sensitivity was assessed by homeostasis model assessment of insulin resistance (HOMA-IR) and hyperinsulinemic euglycemic clamp (M value). Adipocyte size and number were determined.

RESULTS

Of the 130 women with obesity remission, 64 had BF% ≥ 35 and 65 < 35. Independent of BMI, high BF% were associated with higher HOMA-IR (P = 0.021), lower M value (P = 0.0046), higher triglycerides (P = 0.013), higher visceral/total and android/gynoid fat mass ratios (P = 0.0032 and 0.0003 respectively), and larger subcutaneous fat cell volume (P < 0.0001) 2 years after gastric bypass. No differences in anthropometric measures, glucose, blood pressure, or fat cell number were observed.

CONCLUSIONS

Independent of BMI, patients with higher BF% displayed lower insulin sensitivity, higher triglyceride levels, central fat distribution, and larger subcutaneous adipocytes 2 years after gastric bypass. Thus, determination of BF% provides additional information of metabolic characteristics at follow-up of non-obese patients after gastric bypass.