We found moderate changes in mean weight and body composition, with large interindividual variations after one year of lifestyle intervention in children and adolescents with severe obesity and their families. The mean reduction in %IOTF-25 was 3 % in Bergen and 5 % in Tønsberg, and overall 2 of 3 patients showed a decline in %IOTF-25 in the intervention period. This is perceived as a positive change, as clinical experience indicates that the %IOTF-25 of children with severe obesity is generally increasing at the time of referral, which means that over time their BMI moves further above the overweight cut-off value (iso-BMI 25) on the BMI growth chart. In a pilot project conducted in Bergen in the period 2004–2010 with 32 children and adolescents, the %IOTF-25 increased on average 10 % during the two years before the start of treatment (from 152 % to 162 %), and 2 out of 3 patients showed an increase in %IOTF-25 prior to the start of the intervention (13).
A mean decline of 0.08 in BMI standard deviation score is comparable to the most recent Cochrane meta-analyses (3, 4). In Oslo, the Stor og Sterk treatment programme reported in 2011 a mean decline in BMI standard deviation score of 0.13 in 307 children and adolescents after one year (14). This study included patients with a lower degree of obesity and used BMI standard deviation scores based on the Centre for Disease Control and Prevention's BMI reference, which makes direct comparison difficult.
The results of a more intensive follow-up programme with family-based cognitive behavioural therapy for 49 children and their families showed a mean decline in BMI standard deviation score of 0.18 after 12 weeks of intervention (15). Although the mean change in our quality assurance project was small, our figures show wide individual variation. In all, 16.8 % achieved a lower BMI-defined weight class, while 3.4 % went up in weight class, a figure that must nonetheless be viewed in light of the fact that only 91 of 416 could increase their weight class.
Waist circumference is a less frequently used outcome measure. A study from the Netherlands found a change in waist circumference standard deviation score of −0.6 (95 % CI −1.2–0.0) in the course of a one-year family-based intervention in children and adolescents aged 8–17 years (16). This is a considerably larger decline than our findings of -0.03 and -0.11 in Bergen and Tønsberg, respectively. However, the standard deviation scores in this study were based on Dutch references, which may affect the basis for comparison. The change in fat percentage we found was fairly similar to that reported in the most recent Cochrane meta-analyses (3, 4).
BMI standard deviation scores have been widely used as outcome measures in research, but have nonetheless been regarded as unsuitable and potentially misleading for monitoring severe obesity (9, 17, 18). Measurements outside the reference range may lead to the deviation scores not adjusting well enough for age, sex or degree of obesity. Expressing the BMI as a percentage of an overweight cut-off has been proposed as a better measure (19). IOTF overweight cut-off points can be used in this way (%IOTF-25) (9).
As of today, there is no consensus as to how large a change in BMI standard deviation score should be regarded as clinically significant (20). Several studies have found a reduction in cardiovascular risk when the BMI standard deviation score was at least 0.25 units lower, even though this did not necessarily mean that the BMI was below the obesity cut-off (iso-BMI 30) (21, 22). Several studies have also found increased cardiovascular risk with increasing obesity (23), which indicates that weight stabilisation per se can be regarded as a satisfactory therapeutic goal. In our analysis, we found a reduction in BMI standard deviation score of more than 0.25 in 23 % of the participants. %IOTF-25 is a relatively new outcome measure, so there has not been discussion as to how large a change will be clinically significant. However, the IOTF cut-off points have been chosen to correspond to the cut-offs for overweight and obesity in adults. This means that a percentage reduction can be compared directly with a percentage weight loss or BMI reduction in an adult. A weight reduction of more than 5 % is regarded as clinically significant in adults (24). We noted that 42.5 % of participants had a %IOTF-25 reduction of more than 5 %.
We did not find any statistically significant difference in outcome measures between the treatment centres. However, there was a tendency towards a greater weight reduction in Tønsberg, which could be due to an increased exposure of the patients through group meetings, or somewhat larger staffing.
Boys had better weight developments than girls, which has been demonstrated in several earlier studies (25, 26). It is conceivable that biological and psychological differences play a part, and this should be examined more closely. A lower age (<12 years) was related to a larger reduction in BMI and waist circumference standard deviation scores, but did not affect the results for %IOTF-25 or fat percentage. This finding may be the result of a known limitation of standard deviation scores for children with severe obesity (9, 16, 17) and must therefore be interpreted with caution.
Children and adolescents with severe obesity are a very heterogeneous group, which is reflected in their response to intervention. The variation indicates a need for more tools to assist this patient group. It can be assumed that those for whom the standard intervention was unsuccessful require further action. This could be a closer follow-up, extended parental guidance, other approaches such as structured behavioural interventions with the aid of cognitive elements, supplementary treatment with drugs or more invasive measures such as a gastric balloon or weight-reducing surgery.
A substantial proportion dropped out of the programme (27 %), but this share was lower than that reported in most similar studies (27). Inconsistent findings make it difficult to conclude whether there were specific characteristics associated with individuals who dropped out, and also make it difficult to determine how any differences may have influenced the other results. This should be further investigated.
One of the limitations of this quality assessment project is that it only documents weight development over one year. We are therefore unable to say anything about long-term outcome of the programme. The data have been collected from quality registers and represent a retrospective analysis. It is therefore not possible to draw any definite conclusions about efficacy and which aspects of the therapy, if any, have been effective. However, the sample is large, reflects the real situation in the outpatient clinics and forms a basis for describing weight development during an intervention, which has not previously been done in Norway. We do not possess information about the number of consultations carried out at hospitals or in the primary health service.
Large interindividual differences in the development of body weight and body composition during treatment are evidence of the need for research to identify criteria for a successful intervention. This was also proposed by Mead et al. in a Cochrane review (3). Studies of this nature may potentially identify factors that are predictors for effective treatment, so that we are able to determine individual needs and adjust the therapy accordingly in the future.