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AMOS: Insights into adolescent bariatric surgery

LRYGB appears well-tolerated and equally as effective in adolescents as in adults regarding weight loss and metabolic improvements

Bariatric surgery in adolescents appears well-tolerated and equally as effective in adolescents as in adults with regard to weight loss and metabolic improvements, whilst also improved the bone mineral density (BMD)-Z in patients bring the majority of individuals back in line with the non-obese population within two years. These were the conclusion from two presentations by Dr Andrew J Beamish from the Royal College of Surgeons (England) and based on the latest data from the Swedish Adolescent Morbidity Obesity Surgery (AMOS) study. The research was presented at the 6th Annual Meeting of the British Obesity and Metabolic Surgical Society 21-23 January, in Newcastle, UK. 

AMOS is a Swedish nationwide study assessing the safety and efficacy of using laparoscopic RYGB in severely obese adolescents. As well as examining the outcomes from surgery the researchers also looked at changes in bone metabolism and structure. No previous study has reported serum bone markers to assess bone turnover after bariatric surgery in the adolescent, explained Beamish.

Between 2006-2009, the study 81 patients (65% female) underwent surgery. Prior to surgery the patents had a prospective DXA body composition and serum bone marker analysis and at one- and two-year follow up. There were also two control groups comprised 81 conservatively managed adolescents (43% boys), and 81 gender-matched obese adults (aged 35–45 years) undergoing gastric bypass, within ±1 month of the operated adolescents.

Andrew Beamish

The mean weight and BMI at inclusion by group were: surgery group 133kg, 45.5kg; control group 124kg, 42.2kg; and adult group 127kg, 43.5kg. At five-year postoperative follow-up mean weight and BMI in surgery group were 96kg (total weight loss 27%) and 32kg (p<0.001); while a 10% weight gain was observed in control group. Mean weight loss in adult group was 37kg (29%) to reach a mean BMI 31kg.

Waist circumference decreased from 134 to 98cm in Surgery group (p<0.001), and cardiovascular risk factors and inflammatory markers were significantly reduced in Surgery vs. Control adolescent groups. There were eleven (13.6%) laparoscopic remedial operations, indications including internal hernia and symptomatic gallstone disease. Unresolved problems were observed in patients with known neuropsychiatric or psychiatric diagnoses, or hidden addiction at baseline.

There were noted changes in the body composition including a reduction in the percentage fat mass (51.8% to 40.9%, p<0.0001) and relative increase in (preservation of) lean mass (47.0% to 56.8%, p<0.0001). Boys lost more fat than girls (-17.3% vs. -9.5%, p<0.0001).

BMD-Z at baseline was within or above the normal range of -1 to 1 in all subjects. The mean BMD-Z was 1.85 +/ baseline, decreasing to 0.52 +/-1.18 at two years. Four patients reached >1 standard deviation (SD) below the accepted mean for age and gender at two years, all of whom began from a low baseline (-0.6 to -0.5). None was >2 SD below baseline.

Bone markers demonstrated a greater bone turnover in boys than girls at baseline, with increased concentrations of serum markers of bone resorption (CTX p<0.0001) and synthesis (osteocalcin p<0.0001, P1NP p=0.003) were observed after LRYGB, rising in the first year, before more modest reductions in the second. Absolute levels of these markers were higher in boys, in whom skeletal maturity is known to occur later.

Low vitamin levels were reported in 55 patients despite receiving supplements.

Bemish said that overall LRYGB appears well-tolerated and equally as effective in adolescents as in adults regarding weight loss and metabolic improvements and was generally well tolerated. About one in seven needed a remedial surgical procedure, possibly preventable.

He also added that post-operative psychosocial support is necessary in this group of patients.

With regards to gone bone turnover, this increased significantly following LRYGB, with marked differences in the changes in body composition of adolescent males and females following surgery; males lost more fat and preserved more lean mass than females.

“The downward trend in BMD-Z appears to bring the majority of individuals back in line with the non-obese population within two years, but it will be crucial to observe and test this cohort in the longer-term, remaining particularly vigilant for potential or actual clinically relevant reductions,” he concluded.

The presentation, “Bone health in adolescents following Roux-en-Y gastric bypass”, received First Prize Award in the BOMSS Council Prize Session.

Co-authors of the study were Claude Marcus2, Eva Gronowitz3, S Mårlid3, C-E Flodmark4, G Göthberg3, P Friberg3, K Ekbom2, Jovanna Dahlgren3, and Torsten Olbers3 (2Karolinska Institute, Stockholm, Sweden, 3Sahlgrenska University Hospital, Gothenburg, Sweden, 4Skånes University Hospital, Malmö, Sweden).

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