How Does Fat Mass Change in the First Year After Bariatric Surgery? A Systemic Review and Meta-Analysis

The circulating and central endocannabinoid system in obesity and weight loss

Major advances have been made in obesity treatment, focusing on restoring disturbances along the gut-brain axis. The endocannabinoid system (ECS) is a neuromodulatory signaling system, present along the entire gut-brain axis, that plays a critical role in central and peripheral regulation of food intake and body weight. Evidence on the impact of weight loss on the ECS is, however, more limited. Therefore, we set out to review the existing literature for changes in central and circulating endocannabinoid levels after bariatric surgery and other weight loss strategies in humans. The PubMed, Embase and Web of Science databases were searched for relevant articles. Fifty-six human studies were identified. Most studies measuring circulating 2-arachidonoylglycerol (2-AG) found no difference between normal weight and obesity, or no correlation with BMI. In contrast, studies measuring circulating arachidonoylethanolamine (AEA) found an increase or positive correlation with BMI. Two studies found a negative correlation between BMI and cannabinoid receptor type 1 (CB1) receptor availability in the brain. Only one study investigated the effect of pharmacological weight management on circulating endocannabinoid concentrations and found no effect on AEA concentrations. So far, six studies investigated potential changes in circulating endocannabinoids after bariatric surgery and reported conflicting results. Available evidence does not univocally support that circulating endocannabinoids are upregulated in individuals with obesity, which may be explained by variability across studies in several potential confounding factors (e.g. age and sex) as well as heterogeneity within the obesity population (e.g. BMI only vs. intra-abdominal adiposity). While several studies investigated the effect of lifestyle interventions on the circulating ECS, more studies are warranted that focus on pharmacologically and surgically induced weight loss. In addition, we identified several research needs which should be fulfilled to better understand the role of the ECS in obesity and its treatments.

Body Composition Differences Between Excess Weight Loss ≥ 50% and < 50% at 12 Months Following Bariatric Surgery

Background

The relationship between weight loss and body composition is undefined after bariatric surgery. The objective of this study was to compare body composition changes in patients with excess weight loss ≥ 50% (EWL ≥ 50) and < 50% at 12 months post-operatively (EWL < 50).

Methods

A prospective cohort study was completed on patients undergoing bariatric surgery at two tertiary hospitals between 2017 and 2021. Body composition was measured with dual-energy X-ray absorptiometry immediately before surgery, and at 1, 6, and 12 months post-operatively. Body mass index (BMI), fat mass (FM), lean body mass (LBM), and skeletal muscle index (SMI) trajectories were analysed between patients with EWL ≥ 50% and EWL < 50%.

Results

Thirty-seven patients were included in this series (EWL ≥ 50% n = 25, EWL < 50% n = 12), comprising of both primary and revisional bariatric surgery cases, undergoing a sleeve gastrectomy (62.2%), Roux-en-Y gastric bypass (32.4%), or one anastomosis gastric bypass (5.4%). The EWL ≥ 50% group demonstrated a more optimal mean FM-to-LBM loss ratio than the EWL < 50% group. EWL ≥ 50% patients lost 2.0 kg more FM than EWL < 50% patients for each 1 kg of LBM lost. EWL ≥ 50% was also associated with an increase in mean SMI% over 12 months (5.5 vs. 2.4%; p < 0.0009). Across the whole cohort, the first month after surgery accounted for 67.4% of the total LBM reduction that occurred during the 12-month post-operative period.

Conclusion

This data suggests EWL ≥ 50% is associated with a more optimal body composition outcome than EWL < 50%. LBM reduction occurs predominantly in the early post-operative period.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-022-06128-3.

Effects of Roux-en-Y Gastric Bypass Versus Sleeve Gastrectomy on Body Composition for Patients with a BMI > 35 kg/m2 at 1 Year After Surgery

PURPOSE

Effects of Roux-en-Y gastric bypass (RYGB) versus sleeve gastrectomy (SG) on body composition have not been well compared. This meta-analysis aimed to compare changes in fat mass (FM) and lean tissue mass (LTM) for patients with a BMI > 35 kg/m² at 1 year after RYGB and SG.

METHODS

PubMed, EMBASE, the Cochrane Library, and ClinicalTrials.gov were searched ending in December 2021 for eligible studies which reported baseline and postsurgical BMI, FM, and LTM.

RESULTS

Of 17 eligible studies, 831 patients were included, 484 following RYGB and 347 following SG. Weighted mean differences (WMD) and 95% confidence intervals (CI) were from a random-effects model. For patients with a BMI > 35 kg/m², RYGB resulted in a more substantial reduction of BMI (- 14.13 kg/m² [95%CI - 14.74, - 13.53] versus - 11.96 kg/m² [95%CI - 12.81, - 11.11], P < 0.001) and FM (- 26.22 kg [95%CI - 28.31, - 24.12] versus - 21.50 kg [95%CI - 25.52, - 17.48], P = 0.042) than SG, and a relatively weaker impact on LTM (- 8.28 kg [95%CI - 9.33, - 7.22] versus - 10.12 kg [95%CI - 11.55, - 8.68], P = 0.043).

CONCLUSION

This meta-analysis study indicates that RYGB is superior to SG in reducing excess FM for patients with a BMI > 35 kg/m² and seems to be more beneficial when LTM preservation is taken into consideration.

Trajectory Analysis and Predictors of the Percentage of Body Fat Among Chinese Sleeve Gastrectomy Patients

BACKGROUND

The weight loss in Chinese patients after sleeve gastrectomy is different, and the differences can be evaluated through the trajectories of the percentage of body fat (BF%). Patients' baseline psychosocial factors may be associated with these trajectories.

MATERIALS AND METHODS

We selected 267 patients who received sleeve gastrectomy for the first time. The BF% at baseline and 1, 3, 6, 12 months after surgery and baseline psychosocial variables were retrospectively collected. The trajectory model was established according to BF% based on the growth mixture model. The baseline psychosocial variables were compared among different trajectory classes.

RESULTS

Four types of trajectory classes were obtained. The differences in preoperative dietary self-efficacy, exercise self-efficacy, depression, social support, working status, alcohol consumption, and gender among the classes were statistically significant. The pairwise comparison of the above variables revealed that the differences of gender, dietary self-efficacy and exercise self-efficacy among classes were highly effective.

CONCLUSION

Female gender, low dietary self-efficacy and low exercise self-efficacy were predictors for poor BF% trajectory in sleeve gastrectomy patients. Health professionals can early identify patients who are most likely to lose weight in a not-ideal manner based on the above predictors.

Nutritional Management in Bariatric Surgery Patients

The obesity epidemic, mainly due to lifestyle changes in recent decades, leads to serious comorbidities that reduce life expectancy. This situation is affecting the health policies of many nations around the world. Traditional measures such as diet, physical activity, and drugs are often not enough to achieve weight loss goals and to maintain the results over time. Bariatric surgery (BS) includes various techniques, which favor rapid and sustained weight loss. BS is a useful and, in most cases, the best treatment in severe and complicated obesity. In addition, it has a greater benefit/risk ratio than non-surgical traditional therapies. BS can allow the obese patient to lose weight quickly compared with traditional lifestyle changes, and with a greater probability of maintaining the results. Moreover, BS promotes improvements in metabolic parameters, even diabetes remission, and in the quality of life. These changes can lead to an increase of life expectancy by over 6 years on average. The nutrition of people before and after BS must be the subject of indications from a trained staff, and patients must be followed in the subsequent years to reduce the risk of malnutrition and the associated problems. In particular, it is still debated whether it is necessary to lose weight prior to surgery, a procedure that can facilitate the surgeon's work reducing the surgical risk, but at the same time, lengthens preparation times increasing the risks associated with concomitant pathologies. Furthermore, preventing nutritional deficiencies prior to the intervention can improve the results and reduce short- and long-term mortality.