AMOS2 (Adolescent Morbid Obesity Surgery)
Phase: NA
Conditions: Obesity, Diabetes, Hypertension, Steatohepatitis, Inflammation
Sponsor: Göteborg University

Contemporary Clinical Trials Communications 19 (2020) 100592
Available online 27 June 2020
2451-8654/© 2020 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Contents lists available at ScienceDirect 
Contemporary Clinical Trials Communications 
A randomized controlled trial comparing intensive non - surgical treatment 
with bariatric surgery in adolescents aged 13 – 16 years (AMOS2): 
Rationale, study design, and patient recruitment 
Annika  Janson a , b , * , Kajsa  Järvholm c , d , Eva  Gronowitz d , Lovisa  Sjögren d , Sven  Klaesson e , f , 
My  Engström g , h , Markku  Peltonen i , Kerstin  Ekbom b , Jovanna  Dahlgren d , Torsten  Olbers j , k 
a National Childhood Obesity Centre, Karolinska University Hospital, Sweden 
b Division of Pediatric Endocrinology, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden 
c Childhood Obesity Unit, Skåne University Hospital, Malmö, Sweden 
d Region Västra Götaland, Pediatric Obesity Center, Sahlgrenska University Hospital, Gothenburg, Sweden 
e Department of Women's and Children's Health, Södertälje Hospital, Sweden 
f Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden 
g Institute of Health and Care Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden 
h Region Västra Götaland, Department of Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden 
i National Institute for Health and Welfare, Helsinki, Finland 
j Department of Gastrosurgical Research, Sahlgrenska University Hospital, Gothenburg, Sweden 
k Department of Biomedical and Clinical Sciences and Wallenberg Center for Molecular Medicine, Linköping University, Linköping, Sweden and Department of Surgery, 
Vrinnevi Hospital, Norrköping, Sweden 
A R T I C L E  I N F O  
Keywords : 
Adolescents 
Bariatric surgery 
Low - calorie diet 
Obesity 
Pediatric 
Roux - en Y gastric Bypass 
A B S T R A C T  
Background : Pre vi ous non - randomized stud ies show sim i lar out comes in ado les cents and adults af ter bariatric 
surgery. We de scribe the study pro to col, re cruit ment, and se lected base line data of pa tients in a ran dom ized 
multi - center study, the Ado les cent Mor bid Obe sity Surgery 2 (AMOS2). 
Methods : Three clin ics in Swe den col lab o rated in de sign ing the study and re cruit ment of pa tients from Au gust 
1, 2014 to June 30, 2017. Pa tients were se lected among ado les cents 13 – 16 years of age at tend ing third - level 
obe sity care for at least one year. Pa tients were ran dom ized 1:1 to bariatric surgery (pre dom i nantly Roux - en - Y 
gas tric by pass) or in ten sive non - surgical treat ment start ing with an eight - week low - calorie - diet. 
Results : Fifty ado les cents (37 girls) were ran dom ized, 25 (19 girls) to bariatric surgery. Mean age was 15.7 
years (range 13.3 – 16.9), weight 122.6  kg (range 95 – 183.3), Body Mass In dex (BMI) 42.6  kg/ m 2 (range 35.7 – 
54.9) and BMI - SDS 3.45 (range 2.9 – 4.1). One pa tient had type 2 di a betes mel li tus, and 12/ 45 (27%) had el e - 
vated liver en zymes. There were no sig nif i cant dif fer ences be tween the groups. For the 39 el i gi ble pa tients 
who were of fered but de clined in clu sion, BMI was not dif fer ent from in cluded pa tients. How ever, pa tients who 
de clined were younger, 15.2 years (p  =  0.021). A sex dif fer ence was also noted with more of el i gi ble girls, 
37/ 53 (69.8%), than boys, 13/ 36 (36.1%), want ing to par tic i pate in the study (p  =  0.002). 
Conclusions : This clin i cal trial, ran dom iz ing ado les cents with se vere obe sity to bariatric surgery or in ten sive 
non - surgical treat ment, aims at in form ing about whether it is ben e fi cial to un dergo bariatric surgery in early 
ado les cence. It will also en lighten the out come of com pre hen sive non - surgical treat ment. The study was reg is - 
tered at www. clinicalTrials. gov num ber NC T02378259. 
Abbreviations : AMOS2 , Adolescence Morbid Obesity Study 2 , BMI , Body Mass Index , BORIS , Swedish Childhood Obesity Treatment Register , DXA , Dual Energy 
X - Ray Absorptiometry , GB , Roux - en - Y Gastric Bypass , LCD , Low - Calorie Diet , SOReg , Scandinavian Obesity Surgery Registry 
* Corresponding author. Specialist in Pediatrics and Adolescent Medicine, National Childhood Obesity Centre, Astrid Lindgrens Barnsjukhus, Karolinska 
University Hospital Liljeholmstorget 7, plan 8, SE, 117 94, Stockholm, Sweden. 
E - mail addresses: annika. janson@ sll. se (A. Janson), kajsa. jarvholm@ gu. se (K. Järvholm), eva. gronowitz@ vgregion. se (E. Gronowitz), lovisa. sjogren@ vgregion. 
se (L. Sjögren), sven. klaesson@ ki. se (S. Klaesson), my. engstrom@ gu. se (M. Engström), markku. peltonen@ thl. fi (M. Peltonen), kerstin. ekbom@ sll. se (K. Ekbom), 
jovanna. dahlgren@ gu. se (J. Dahlgren), torsten. olbers@ liu. se (T. Olbers). 
https://doi.org/10.1016/j.conctc.2020.100592 
Received 12 February 2020; Received in revised form 8 June 2020; Accepted 14 June 2020 

Contemporary Clinical Trials Communications 19 (2020) 100592
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A. Janson et al. 
1 . Introduction 
De spite some coun tries re port ing that obe sity is lev el ing off, the 
num ber of ado les cents with se vere obe sity is in creas ing world wide 
[ 1 – 7 ]. Treat ment with lifestyle mod i fi ca tions has lim ited ef fects [ 8 ]. 
Bariatric surgery is the stan dard treat ment for se vere obe sity in 
adults. In Swe den, there is a strong com mit ment to na tional guide - 
lines lim it ing bariatric surgery be fore 18 years to stud ies [ 9 ], al - 
though there is ac cu mu lat ing ev i dence for sim i lar ef fi cacy as in adult 
pa tients. In the Ado les cent Mor bid Obe sity Surgery (AMOS) study, 81 
ado les cents un der went Roux - en - Y gas tric by pass. They lost, on av er - 
age, 36.8   kg, which was sim i lar to matched adult con trols, and im - 
proved meta bolic risk fac tors. Gas tric by pass was, how ever, as so ci ated 
with ad di tional sur gi cal in ter ven tions and nu tri tional de fi cien cies, and 
nine (11%) of the ado les cent pa tients had lost less than 10% of their 
ini tial weight at the five - year fol low up [ 10 ]. 
Sim i lar marked weight loss was also demon strated for both groups 
in the Teen - Longitudinal As sess ment of Bariatric Surgery (Teen - LABS) 
study, where 161 ado les cent pa tients were com pared to an adult 
group who had obe sity at 18 years of age. Ado les cent pa tients were 
sig nif i cantly more likely to have re mis sion of type 2 di a betes and hy - 
per ten sion than adults [ 11 , 12 ]. How ever, an is sue of con cern was two 
deaths as so ci ated with sub stance abuse in the ado les cent group, al - 
though no sig nif i cant dif fer ence in mor tal ity be tween the groups was 
ob served. The pro por tion of pa tients that lost less than 5% of ini tial 
weight or in creased in weight was sig nif i cantly larger in the ado les - 
cent group [ 12 ]. In a ran dom ized study in ado les cents com par ing la - 
paro scopic ad justable gas tric band and in ten sive con ser v a tive treat - 
ment, 84% of op er ated pa tients lost half of their ex cess weight in con - 
trast to only 12% in the con trol group. Eight of the 25 pa tients needed 
ad di tional re vi sional sur gi cal pro ce dures [ 13 ]. 
Stud ies in ado les cents have also shown that longer - term weight 
loss seems to be dri ven by weight out comes by 12 months post - 
surgery, whereas pre op er a tive weight loss from time of in take to time 
of surgery did not show an as so ci a tion with weight out comes. This 
sug gests that ado les cent pa tients who lose more weight pre - surgery 
are not nec es sar ily the in di vid u als who lose more weight post - surgery 
[ 14 ]. 
Re gard less of weight, ado les cence is a vul ner a ble pe riod in life 
with sub stan tial phys i cal, so cial, cog ni tive, and psy cho log i cal trans - 
for ma tions [ 15 , 16 ]. Ado les cents with obe sity have a higher preva - 
lence of con comi tant psy chi atric dis ease than nor mal - weight peers, 
and so cio - economic dis ad van tages are more com mon [ 17 , 18 ]. In a re - 
view, bariatric surgery was as so ci ated with sus tain able im prove ment 
of qual ity of life in ado les cents [ 19 ]. In the AMOS - study, self - concept 
and self - esteem im proved sig nif i cantly so that ado les cents achieved a 
level of men tal health and self - concept com pa ra ble to norms two 
years af ter bariatric surgery [ 20 ]. How ever, one in five ado les cents re - 
ported sub stan tial men tal health prob lems af ter surgery, and base line 
men tal health prob lems were as so ci ated with poor men tal health af ter 
surgery [ 21 ]. Men tal health prob lems per sisted in ado les cents five 
years af ter bariatric surgery de spite sub stan tial weight loss [ 22 ]. 
The promis ing re sults of stud ies on bariatric surgery are al ready 
in flu enc ing clin i cal prac tice in many coun tries, but ques tions re gard - 
ing the op ti mal time point for bariatric surgery have been raised [ 23 ]. 
The ef fect of surgery in re la tion to pu ber tal de vel op ment and growth 
spurt as well as men tal de vel op ment, au ton omy, and so cial func tions 
need fur ther eval u a tion, and sex dif fer ences need to be ex plored. 
There fore, we de signed a ran dom ized clin i cal trial to com pare out - 
comes from in ten sive non - surgical treat ment ver sus bariatric surgery 
for ado les cents 13 – 16 years old with se vere obe sity. 
2 . Materials and methods 
2. 1 . Study area 
AMOS2 is a na tion wide Swedish study. Three ter tiary child hood 
obe sity treat ment clin ics in uni ver sity hos pi tals in the three largest 
cities of Swe den in cluded pa tients. These clin ics also ac cepted re fer - 
rals from other parts of the coun try. 
2. 2 . Study population 
All pa tients be tween 13 and 16 years of age who had been treated 
for obe sity for at least 12 months were screened for el i gi bil ity. 
2. 3 . Recruitment procedures 
Pa tients in the se lected age group were screened for el i gi bil ity for 
the study in multi - professional team - based dis cus sions. Pa tients were 
con sid ered el i gi ble pro vided: 1) 13 – 16 years of age 2) BMI ≥35 and 
3) un der gone at least 12 months of obe sity treat ment with in suf fi cient 
ef fect, of which at least six months at the in clud ing clinic. Pa tients 
should be in pu ber tal stage Tan ner 3, or higher, and ob vi ous ex clu sion 
cri te ria should not be pre sent. 
In for ma tion about the study was dis trib uted at the clin ics and a 
study - specific web page, www. amos2. se . An ado les cent or a fam ily 
could also ini ti ate an eval u a tion for con sid er a tion of bariatric surgery, 
which then was fol lowed by the same team - discussion and screen ing 
for el i gi bil ity. 
El i gi ble pa tients were in formed about the study at a visit to the 
clinic. A thor ough in ves ti ga tion was ini ti ated if pa tients were in ter - 
ested in par tic i pat ing in the study. The in ves ti ga tion aimed at iden ti - 
fy ing ex clu sion cri te ria, eval u ate the abil ity of the pa tient to make an 
in formed de ci sion, and pro vide in for ma tion about the study de sign 
and pro ce dures. Dur ing this in ves ti ga tion, pa tients had ap point ments 
with a pe di a tri cian, a nurse, and a psy chol o gist, of ten sev eral times. 
We in formed the ado les cent and their fam i lies that bariatric 
surgery might be come a treat ment al ter na tive at some point in their 
life. Fam i lies were in formed that the study aimed at ex plor ing 
whether there are ben e fits from un der go ing surgery in ado les cence in 
com par i son to later. Treat ment arms were pre sented with equipoise 
stat ing that “we don't know whether it is bet ter to un dergo surgery in 
ado les cence or later”. 
Group in for ma tion ses sions fa cil i tated fur ther in for ma tion ex - 
change be tween clin i cians and ado les cents and their par ents, usu ally 
with the sur geon pre sent. Fam i lies were in formed that surgery was 
cen tral ized to one cen ter (Gothen burg). For plan ning rea sons, pa tients 
were as signed a ten ta tive date for surgery, al ter na tively a date for 
start ing the low - calorie diet for two or eight weeks, re spec tively, de - 
pend ing on ran dom iza tion. 
2. 4 . Inclusion and exclusion criteria 
2. 4. 1 . Inclusion criteria 
• Age 13 – 16 years 
• BMI > 35  kg/ m 2 
• Insufficient results from comprehensive treatment for obesity for at 
least one year 
• Eligible according to the assessment of psychologist 
• Pubertal stage Tanner 3 or higher 
2. 4. 2 . Exclusion criteria 
• Monogenic or syndromic obesity (for example Prader Willi 
Syndrome, Laurence Moon - Bardet - Biedl) 

Contemporary Clinical Trials Communications 19 (2020) 100592
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A. Janson et al. 
• Obesity secondary to brain injury 
• Severe 
intellectual 
disability 
or 
other 
severe, 
pervasive 
developmental disorder 
• Not eligible for general anesthesia 
• Psychosis or other major psychiatric illness (i. e., severe depression 
or suicide attempt during the last year). Self - induced vomiting to 
regulate weight. 
• Ongoing substance abuse 
• Previous major gastrointestinal surgery 
For safety rea sons, we also ex cluded pa tients with sub stan tial 
prob lems re lated to ad her ence, such as miss ing most ap point ments, as 
we an tic i pated se vere prob lems in the study fol low - up if they were in - 
cluded. A lim ited num ber of pa tients with man i fest com pli ca tions to 
obe sity, such as type 2 di a betes mel li tus, were con sid ered in el i gi ble 
for the study for eth i cal rea sons. In stead, they were con sid ered to 
have an “im per a tive clin i cal in di ca tion” for in ter ven tion. They were 
re ferred for bariatric surgery, usu ally at age 16 – 18 years, af ter a de ci - 
sion in the study steer ing com mit tee. 
2. 5 . Modification of protocol 
Ini tially, we aimed at in clud ing ado les cents 13 – 15 years of age. Af - 
ter six months, we changed to 13 – 16 years in re sponse to the age - 
distribution of the pa tients at the clin ics and their will ing ness to ac - 
cept par tic i pa tion in the study. Study vis its in the trial were changed 
from 6 weeks, 1, 2, 7, 12, and 17 years af ter in clu sion in the orig i nal 
plan to 6 weeks, 1, 2, 5, 10, and 15 years af ter in clu sion. The rea son 
for this change was to bet ter com ply with the nor mal reg istry - based 
Scan di na vian Obe sity Surgery Reg istry (SOReg) in ter vals used for 
long - term fol low up. The clinic in Malmö joined the study on May 1, 
2015. 
2. 6 . Investigations at baseline and randomization procedures 
Pa tients who were deemed el i gi ble by the team and ac cepted in - 
clu sion were sched uled for an in clu sion visit. In clu sion visit lasted one 
or two days and in cluded: 1) base line in ves ti ga tions 2) ex am i na tion 
by a pe di a tri cian 3) dis cus sion with a pe di atric nurse re gard ing lo gis - 
tics and par tic i pa tion 4) a di eti cian as sisted in reg is tra tion of eat ing 
pat terns and food choices us ing val i dated in stru ments and 5) a psy - 
chol o gist as sessed psy cho log i cal well - being us ing val i dated in stru - 
ments. A phys io ther a pist as sisted in per form ing a stan dard ized sub - 
maximal fit ness test for aer o bic ca pac ity ex pressed as the max i mum 
rate of oxy gen con sump tion (VO 2 max) that was per formed at two of 
the cen ters. Dual En ergy X - Ray Ab sorp tiom e try (DXA) was per formed 
for as sess ing body com po si tion. Blood sam ples were col lected for 
analy sis and stor age, and an Oral Glu cose Tol er ance Test (OGTT) was 
per formed. Pa tients who were pre scribed met formin were asked not 
to take the drug 1 – 2 days be fore the OGTT. 
At the end of the in clu sion visit, com put er ized ran dom iza tion was 
per formed at a re search lab in Gothen burg. The cen ter was in formed 
over e - mail or tele phone. The staff at the in clud ing cen ter in formed 
the pa tient. Ran dom iza tion was per formed as 1:1 in a pro gram strat i - 
fy ing to en sure even num bers of surgery and non - surgery pa tients of 
both sexes at each site. 
The BMI from a mea sure ment of weight and height at the in clu - 
sion visit is the base line BMI for each pa tient in the study. BMI Z 
scores were cal cu lated us ing the IOTF - reference [ 24 ]. 
2. 7 . Interventions 
2. 7. 1 . Intensive non - surgical treatment 
Pa tients were pro vided low - calorie diet (LCD) prod ucts con tain ing 
800   kcal/ day us ing a com mer cial prod uct, Mod i fast (Im polin AB, 
Täby, Swe den), for eight weeks, free of charge. A treat ment in ten sity 
of monthly in ter ac tions with mem bers of the multi - professional team, 
ei ther as phys i cal vis its or tele phone con tacts, was planned for the 
two - year study pe riod. 
2. 7. 2 . Bariatric surgery 
Pa tients were rec om mended LCD prod ucts con tain ing 800   kcal/ 
day, Mod i fast (Im polin AB, Täby, Swe den), for two weeks. Af ter that, 
pa tients un der went bariatric surgery. The sur gi cal method was de - 
cided by the sur geon af ter dis cus sions with the fam ily. La paro scopic 
Roux - en - Y Gas tric By pass was per formed in all cases ex cept in two pa - 
tients where sleeve gas trec tomy was the pre ferred method. Fol low - up 
vis its were sched uled af ter six weeks and 6, 12, 18, and 24  months  at 
the clinic. Seven vis its were planned in the pro to col over the ini tial 
study pe riod of two years. Sup ple men tary vi t a mins and min er als were 
pro vided by the study free of charge. 
2. 8 . O utcome measures 
The pri mary out come of the study is the dif fer ence in changes in 
BMI over two years be tween the sur gi cal and non - surgical treat ment 
arms. The sec ondary out comes will be dif fer ences in the de vel op ment 
of car dio vas cu lar ill ness and can cer, bio chem i cal mark ers of meta - 
bolic health, body com po si tion, bone health, phys i cal fit ness, qual ity 
of life, and psy cho log i cal and cog ni tive func tion ing. Both the pri mary 
and sec ondary out comes will be an a lyzed for 5 - , 10 - and 15 - year 
changes. 
As sess ments are sched uled at 1, 2, 5, 10, and 15 years from base - 
line, in clud ing team - visits for as sess ment of sec ondary out come mea - 
sures: gen eral health, qual ity of life, phys i cal per for mance, bone 
health by DXA, bio chem i cal meta bolic sit u a tion, psy choso cial vari - 
ables, cog ni tive func tion ing, men tal health, ad dic tive be hav ior, di - 
etary in take, and eat ing pat terns. In ad di tion, data from manda tory 
cen tral reg istries for as sess ment of health care con sump tion and so cio - 
economic de vel op ment will be col lected. We will also as sess how 
many pa tients in the non - surgical treat ment group that chose to un - 
dergo bariatric surgery later, as well as long - term car dio vas cu lar 
events, can cer in ci dence, and over all mor tal ity. 
2. 9 . Patients declining participation in the study 
Data re gard ing pa tients who were of fered but de clined par tic i pa - 
tion in the study was reg is tered in their clin i cal records as part of the 
screen ing pro ce dure and clin i cal treat ment. For this study, we cat e go - 
rized the main rea son for not want ing to par tic i pate into five broad 
cat e gories: 1. “not in ter ested” (in clud ing those who did not re turn for 
ap point ments); 2. per ceiv ing surgery as “too dras tic”; 3. “it works fine 
as it is”; and 4. “could not han dle LCD for eight weeks” and 5. “not in - 
ter ested in ran dom iza tion to LCD”, where the last two cat e gories 
might be over lap ping. 
2. 10 . Financing 
The study was fi nanced by a grant from Swe den's in no va tion 
agency Vin nova (T. Ol bers, 2012 - 34346 - 95933 - 20 ). The grant re - 
quired a for mal ized part ner ship with par tic i pat ing uni ver sity hos pi tal, 
mak ing costs equally shared to en com pass that the pa tients in the 
study were al ready ac tively treated at the clin ics. Surg eries were pro - 
vided free of charge, both for the pub lic health care sys tem and the 
pa tients, by the non - profit hos pi tal Car lan der ska, Gothen burg, Swe - 
den. 

Contemporary Clinical Trials Communications 19 (2020) 100592
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A. Janson et al. 
2. 11 . Registration 
The study was reg is tered at www. clinicalTrials. gov num ber NC - 
T02378259. 
2. 12 . Study management 
Be sides the prin ci pal in ves ti ga tor, a steer ing com mit tee with par - 
tic i pants from all cen ters and rep re sent ing var i ous pro fes sions was 
mak ing de ci sions in the trial. Monthly tele phone - conferences sup - 
ported de ci sions about all in clu sions in the study. In ves ti ga tors’ meet - 
ings were held twice a year for shar ing study ex pe ri ences and min i - 
mize pro to col de vi a tions. 
2. 13 . Statistics 
The pri mary con clu sions from this study will be based on analy ses 
con ducted un der the prin ci ple of in ten tion - to - treat. Thus, all ran dom - 
ized pa tients will be in cluded in the analy ses, and it is as sumed that 
all ran dom ized pa tients re ceive the treat ment for which they were 
ran dom ized. For the sam ple size cal cu la tion, we as sumed a 2 - year re - 
duc tion in BMI of 15  kg/ m 2 in the surgery group based on the re sults 
of the AMOS - study [ 10 ] with stan dard de vi a tion (SD) 7   kg/ m 2 . Fur - 
ther, we as sumed a re duc tion in BMI of 5  kg/ m 2 in the in ten sive non - 
surgical treat ment group with SD 7   kg/ m 2 . Based on these as sump - 
tions, a to tal sam ple size of 50 (25 in each group) will pro vide > 95% 
power at 0.01 sig nif i cance level to demon strate a dif fer ence in BMI - 
change over two years be tween the groups. In ad di tion, the sam ple 
size was cho sen to al low as sess ment of dif fer ences in car dio vas cu lar 
risk fac tors and dif fer ences in qual ity of life and cog ni tive func tions. 
For com par i son be tween groups at base line, an in de pen dent Stu - 
den t's t - test was per formed, and re sults are pre sented as means with 
stan dard de vi a tion and range. For fur ther analy ses, a dif fer ence in 
treat ment ef fect will be eval u ated with the haz ard ra tio be tween the 
treat ment groups, and the cor re spond ing con fi dence in ter val will be 
cal cu lated. The dif fer ence in BMI - changes be tween the groups will be 
es ti mated with a mul ti level mixed - effect re gres sion model uti liz ing 
BMI mea sure ments at all avail able time points. This model con sid ers 
the re peated mea sure ments nested within per sons over time. All ran - 
dom ized pa tients ex cept those who will with draw their con sent will 
be in cluded in this analy sis. 
2. 14 . Register - based data collection 
All pa tients par tic i pated in the Swedish Child hood Obe sity Treat - 
ment Reg is ter (BORIS) [ 36 ]. Pa tients un der go ing bariatric surgery 
were reg is tered in SOReg. The Swedish Na tional Pa tient Reg is ter col - 
lects data for in - patient as well as out - patient hos pi tal care. 
2. 15 . Ethics 
This mul ti cen ter study was ap proved by the eth i cal board in 
Gothen burg with no 578 – 13. 
3 . Results 
The study pro to col was de signed and re vised, as stated above, and 
the study steer ing com mit tee proved to be a use ful fo rum for col lab o - 
ra tion. Re cruit ment was con tin u ous, as was the ac cep tance of new pa - 
tients at the re spec tive cen ter. The num ber of screened pa tients was 
es ti mated to be around 500 ( Fig. 1 ). The num ber of pa tients 13 – 16 
years of age with obe sity de fined as IOTF - BMI> 30 [ 25 ] at three clin - 
ics mea sured as a point - measurement on Jan u ary 1, 2016 were 473 of 
whom 219 were girls (46.3%). The re spec tive size of the clin ics was 
126 (66 girls) in Gothen burg, 222 (97 girls) in Malmö and 125 (56 
girls) in Stock holm. 
Fifty ado les cents (37 girls, 74%) ful filled the in clu sion cri te ria and 
had no ex clu sion cri te ria, and ex pressed an au tonomous de ci sion 
about will ing ness to par tic i pate in this trial. In ad di tion, con sent was 
ob tained from their par ents or guardians. There were no con flict ing 
opin ions be tween ado les cents and par ents or guardians in any of the 
in cluded cases. 
For in cluded pa tients, the mean age was 15.7 years, weight 
122.6  kg (range 95 – 183.3), and BMI 42.6   kg/ m 2 (range 35.7 – 54.9), 
cor re spond ing to a mean BMI SDS of 3.45 ( Table 1 ). The re cruit ment 
process in the three clin ics was sim i lar, how ever not iden ti cal. The 
Gothen burg clinic in cluded 19 pa tients, Malmö 22, and Stock holm 9 
pa tients. Of in cluded par tic i pants, 21 (42%) had at least one par ent 
who had un der gone bariatric surgery. For pa tients be low 15 years, 7/ 
11 (63.6%) had at least one par ent who had un der gone bariatric 
surgery ( Table 2 ) in con trast to 14/ 39 (35.8%) of pa tients > 15 years, 
but this dif fer ence was not sta tis ti cally dif fer ent (p  =  0.1). 
Fol low ing thor ough in ves ti ga tions by the obe sity team, 14 pa tients 
who were ini tially con sid ered el i gi ble were ex cluded be fore ran dom - 
iza tion ( Fig. 1 ). The rea sons for ex clu sion were re lated to cri te ria, 
such as hav ing a lim ited au ton omy and abil ity to make a well - 
informed de ci sion about the study, or in ves ti ga tions re vealed dis - 
turbed eat ing pat terns, man i fest or sus pected sub stance abuse, or se - 
vere prob lems with com pli ance be ing likely to af fect ad her ence to the 
in ter ven tion and fol low - up. 
Thirty - nine pa tients were of fered in clu sion in the study but de - 
clined par tic i pa tion. The pro por tion ac cept ing an of fer to par tic i pate 
in the study var ied sig nif i cantly be tween gen ders; 37/ 53 (69.8%) of 
girls of fered in clu sion, and 13/ 36 (36.1%) of boys of fered in clu sion 
agreed to par tic i pate (p  =  0.002). 
The main rea son for not want ing to par tic i pate was for 25/ 39 
(64.1%) cat e go rized as “not in ter ested”. Surgery was per ceived “too 
dras tic” for 7/ 39 (17.9%), whereas 5/ 39 (12.8%) said that “it works 
fine as it is”. One pa tient said “could not han dle the LCD for eight 
weeks”, and one pa tient would not ac cept the 1:1 ran dom iza tion to 
the non - surgical treat ment. Pa tients de clin ing par tic i pa tion were sig - 
nif i cantly younger, 15.2 years (±1.17, range 12.7 – 16.9) (p  =  0.021). 
How ever, the mean BMI was 41.3  kg/ m 2 (±5.20, range 35.6 – 52.3), 
which was not sig nif i cantly dif fer ent from in cluded pa tients 
(p  =  0.193). 
Thir teen pa tients be low 17 years of age with meta bolic com pli ca - 
tions to obe sity, such as type 2 di a betes, were of fered bariatric 
surgery on a clin i cal in di ca tion dur ing the study pe riod and were thus 
not in cluded in AMOS2. Ten of these pa tients were 16 – 17 years old, 
and three pa tients were be low 16  years  at the time of surgery. 
3. 1 . Baseline investigations 
Back ground data (mean and SD) are shown in Table 1 . Of in cluded 
(n  =  50) pa tients, 29/ 50 (58%) had im paired glu cose tol er ance (fp - 
glucose> 5.6   mmol/ l) and 12/ 45 (27%) had af fected liver sam ples 
(ala nine amino trans ferase > 0.9   μkat/ l). In to tal, 33/ 50 (66%) had 
some meta bolic im pair ment, mea sured as ei ther im paired glu cose tol - 
er ance or el e vated liver en zymes. There was no dif fer ence be tween 
the groups, with 16 pa tients with af fected meta bolic sta tus in the non - 
surgical treat ment group and 17 in the sur gi cal treat ment group. 
4 . Discussion 
This ar ti cle pre sents the de sign, pa tient re cruit ment, and in clu sion 
process for a ran dom ized con trolled trial com par ing bariatric surgery 
and in ten sive non - surgical treat ment for ado les cents with se vere obe - 
sity (AMOS2). Ran dom iza tion re sulted in sim i lar groups re gard ing 

Contemporary Clinical Trials Communications 19 (2020) 100592
5
A. Janson et al. 
Fig. 1 . Con sort sched ule show ing flow of pa tients in the study Ado les cent Mor bid Obe sity Surgery 2. 
Table 1 
Back ground data of in cluded pa tients. 
Total 
Intensive non - surgical 
treatment 
Bariatric 
surgery 
 
 
n 
n 
Number (female) 
50 (37) 
25 (19) 
25 (18) 
Age (SD) years 
15.7 (1.0) 
15.9 (0.8) 
25 
15.6 (1.1) 
25 
Height (SD) cm 
169.4 
(8.2) 
168.7 (8.2) 
25 
170.2 (8.0 
25 
Weight (SD) kg 
122.6 
(17.5) 
120.9 (21.6) 
25 
124.3 
(14.6) 
25 
BMI (SD) kg/m 2 
42.6 (5.4) 
42.3 (5.5) 
25 
42.9 (5.0) 
25 
BMI SDS [ 24 ] (SD) 
3.45 (0.3) 
3.43 (0.32) 
25 
3.48 
(0.27) 
25 
Waist circumference 
(SD) cm 
122 (11.9) 123.9 (15.5) 
25 
120.2 
(11.5) 
25 
SD=Stan dard de vi a tion, Sign  =  Sig nif i cance, BMI= Body Mass In dex. 
Table 2 
Age dis tri b u tion of in cluded pa tients and num ber of pa tients where at least 
one par ent has un der gone bariatric surgery. 
Age (years) 
13 – 13.9 14 – 14.9 15 – 15.9 16 – 16.9 
Number of patients (female) 
3 (1) 
8 (6) 
15 (13) 
24 (17) 
At least one parent with bariatric 
surgery 
1 
6 
5 
9 
age, BMI, and preva lence of meta bolic dis tur bances be tween treat - 
ment arms. 
Al though a hand ful of out come stud ies are avail able in ado les cent 
bariatric surgery, lit tle is known about ado les cents’ path way to obe - 
sity surgery. An in ter est ing ob ser va tion in our study was that 42% of 
the in cluded pa tients had at least one par ent who had un der gone 
bariatric surgery. Our im pres sion was that this made pa tients and par - 
ents more con fi dent in agree ing to par tic i pate in the trial. There was a 
ten dency that the younger the pa tient, the more com mon it was to 
have a par ent who had un der gone surgery. 
An other ob ser va tion is that 39/ 89 (43.8%) of pa tients el i gi ble for 
in clu sion de clined par tic i pa tion. The most com mon rea son was that 
the pa tient and fam i lies were not “in ter ested”, which we, in most 
cases, in ter preted as not in ter ested in be ing ran dom ized to surgery. A 
sub - group ex pressed that they con sid ered surgery ap pear ing too dras - 
tic. We lack fur ther de tails of the rea son ing as we base our analy sis on 
the doc u men ta tion from the clin i cal records. How ever, the rel a tively 
low ac cep tance rate of par tic i pa tion ap pears im por tant as some may 
ar gue that bariatric surgery is an “easy way” or a “magic bul let” and a 
tempt ing op tion for ado les cents with se vere obe sity. In stead, we be - 
lieve that those ac cept ing in clu sion in this ran dom ized trial had care - 
fully con sid ered par tic i pa tion and were pre pared for both treat ments. 
We pre sented the two study - arms as hav ing clin i cal equipoise, 
with both of them hav ing pos si ble ben e fits as well as draw backs. We 
also tried to eval u ate the young per son's abil ity to en com pass the re - 
main ing is sues of long - term ben e fi cial lifestyle mod i fi ca tions and 
long - term as pects of liv ing with bariatric surgery. A qual i ta tive study 

Contemporary Clinical Trials Communications 19 (2020) 100592
6
A. Janson et al. 
by Doyle et al. have in ves ti gated the de ci sion mak ing from the pa - 
tients' per spec tive, with semi - structured in ter views of nine pa tients 
opt ing for bariatric surgery. They iden ti fied a range of mo ti va tions for 
choos ing surgery, in clud ing a de sire for a bet ter fu ture, to be con fi - 
dent, healthy, and “nor mal” [ 26 ]. 
We noted an in ter est ing sex dif fer ence where the ac cep tance for 
par tic i pa tion was higher among girls de spite a slight ma jor ity of 
screened pa tients were male. The rea sons for these dif fer ences de serve 
fur ther ex plo ration, prefer ably in qual i ta tive re search. A pos si ble rea - 
son might be that se vere obe sity is a more sub stan tial psy choso cial 
bur den for ado les cent girls in com par i son to boys, mak ing girls more 
prone to ac cept an in va sive treat ment as surgery. An other rea son may 
be sex - differences in the pa tients’ ex pe ri ences of the ef fect of pre vi ous 
treat ments. 
The older age span (16 years) con sti tuted al most half of the in - 
cluded pa tients, and pa tients ac cept ing in clu sion were sig nif i cantly 
older than those who de clined. These ob ser va tions again il lus trate 
that bariatric surgery is just emerg ing and be gin ning to be ac cepted as 
a treat ment al ter na tive for the youngest ado les cents. Is sues re gard ing 
the in di vid u al's au ton omy and le gal as pects must be con sid ered when 
treat ing ado les cents. At the same time, the young per son may need a 
ro bust en vi ron ment to re flect and eval u ate long - term as pects of treat - 
ment op tions. A very rel e vant point for young fe male pa tients is 
bariatric surgery in re la tion to fer til ity and preg nancy out comes. In a 
re cent in - depth and com pre hen sive analy sis of all deaths dur ing preg - 
nancy and 42 days af ter de liv ery in Swe den in 2007 – 2017, 15/ 67 of 
de ceased women had BMI> 30  kg/ m 2 , and 4/ 67 had BMI> 45  kg/ m 2 
[ 27 ]. Also, large reg is ter - based stud ies from Swe den show im proved 
out comes for the chil dren born by moth ers af ter bariatric surgery 
com pared to weight - matched con trols with obe sity [ 28 , 29 ]. Col lec - 
tively, these re sults sug gest that bariatric surgery be fore preg nancy 
ap pears ben e fi cial for the mother as well as for the child. 
Bariatric surgery has be come stan dard prac tice in the treat ment of 
ado les cents with se vere obe sity in the United States over the last 
decade, where guide lines state that bariatric surgery should be con sid - 
ered in ado les cents hav ing a BMI > 35  kg/ m 2 and a co - morbidity or 
with BMI > 40  kg/ m 2 [ 30 ]. In con trast, in the UK, the Na tional In sti - 
tute of Clin i cal Ex cel lence states that bariatric surgery may be con sid - 
ered for ado les cents with se vere obe sity in “ex cep tional cir cum - 
stances” [ 31 ]. Sim i larly, when dis cussing the role of bariatric surgery 
in ado les cents with non - alcoholic steato hep ati tis, the Eu ro pean So ci - 
ety for Pe di atric Gas troen terol ogy, He pa tol ogy, and Nu tri tion in 2016 
stated that “Fu ture stud ies and a long - term risk analy sis of pa tients 
with obe sity as so ci ated liver dis ease are much needed to clar ify the 
ex act in di ca tions for bariatric surgery in ado les cents” [ 32 ]. In Swe - 
den, the cur rent guide lines with an age limit of 18 years have been in - 
creas ingly ques tioned in light of the on go ing AMOS pro jects [ 33 ]. 
Also, ran dom ized stud ies are on go ing in adults to com pare dif fer ent 
sur gi cal tech niques, and these re sults will likely ben e fit also the 
younger pa tients where the long - term re sults of surgery will be even 
more crit i cal [ 34 , 35 ]. 
Still, data un der pin ning a sur gi cal strat egy are rel a tively scarce, 
and ran dom ized clin i cal tri als are lack ing. De spite the need for con - 
trolled stud ies - that we hope to ad dress with AMOS2 - the risks of not 
per form ing bariatric surgery need to be con sid ered when com par ing 
risks and ben e fits in treat ing se vere obe sity in ado les cents. Stud ies 
demon strate a high risk of ag gra vated med ical and psy choso cial com - 
pli ca tions, along with sub stan tial fur ther weight gain with out in ter - 
ven tion. In creased aware ness about bariatric surgery as a treat ment 
op tion leads to more re quests from pa tients and par ents. Con cerns re - 
gard ing the long - term ef fects of bariatric surgery, such as bone health 
and risk for sub stance abuse, are es pe cially valid for younger pa tients. 
The tim ing of surgery, if per formed, be comes a highly rel e vant is sue. 
5 . Conclusions 
AMOS2 is a ran dom ized clin i cal trial com par ing bariatric surgery 
(Roux - en - Y gas tric by pass or gas tric sleeve) and in ten sive non - surgical 
treat ment in ado les cents with se vere obe sity. We in cluded 50 pa tients 
in AMOS2, and there were no sig nif i cant dif fer ences be tween the two 
study groups at in clu sion. The main sci en tific ques tion ad dresses 
whether it is ben e fi cial to un dergo bariatric surgery dur ing ado les - 
cence or whether an in ten sive non - surgical pro gram can be a bet ter 
op tion. 
5. 1 . Limitations 
All par tic i pants had to be pre pared to ac cept the two al ter na tives 
(in tense treat ment with LCD and bariatric surgery) be fore in clu sion. 
This de sign may have made pa tients de sir ing sur gi cal treat ment more 
likely to take part as surgery was not an op tion out side con trolled 
stud ies in Swe den. How ever, great ef forts were in vested in pre sent ing 
both treat ments as at trac tive, and both groups had a higher in ten sity 
in treat ment than stan dard care. Pa tients were in formed be fore ran - 
dom iza tion that they could be as sessed for surgery af ter the study pe - 
riod if ran dom ized to non - surgical treat ment. 
El i gi ble ado les cents with se vere obe sity who had se vere meta bolic 
com pli ca tions, such as type 2 di a betes, were of fered bariatric surgery 
on a clin i cal in di ca tion (n  =  13) dur ing the pe riod of in clu sion. 
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