Opt-in and dropout rate

GCWMS offers longer term support, of up to two years, to individuals who choose to continue losing weight. However, some patients choose to leave the programme after the first or second month, possibly due to factors such as weight regain, failure to lose weight, or confidence brought about by their weight loss success, as they believe they can follow the same treatment plan at home independently without the assistance of the service. This explains the reasons for the missing data and using the LOCF method. A previous study (n

=124), which recruited patients with BMI >30 kg/m² from outpatients’ clinic in Croatia or via GP referral to a weight management study for 12 months, was performed to identify factors that predict dropout rates. This study found the overall drop rate was 32.3% and resulted from reasons ranging from lack of motivation (15.3%), to psychological problems or health-related issues (8.0%). Moreover, it was not possible to contact the patients (6.4%)

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due to unhappiness with the programme (2.4%); in addition to their lower education level (Hadziabdic et al., 2015).

Young patients dropped out of the programme at a higher rate than older people (81.5% of young patients aged 18-29 years dropped out) and this result is consistent with previous findings of the multidisciplinary tier 3 of the Fakenham weight management service (FWMS) (Jennings et al., 2014). It was found that the mean age of participants who were assessed but not recruited was lower than those who attended (45.2 vs. 52.7 years, p

=0.001). A possible explanation of this might be the priority given to family members and children or work commitments. Another possible explanation is insufficient weight loss reducing their motivation to attend sessions.

Moreover, patients from the most deprived areas were more likely to drop out, as only 26.5% of the total number of patients referred turned up. This could be due to a lack of transportation or the need to prioritise work. A higher proportion of patients with BMI ≥50 kg/m² had turned up, possibly due to their concern that their body weight was damaging their overall health. In contrast, a RCT (2 year’s duration in the US) compared weight loss achieved through self-help weight loss and with a designed commercial programme (12 weeks), and suggested that most of the patients who dropped out had higher starting BMIs (Heshka et al., 2003). This discrepancy could be due to the difference in the BMI at baseline between the two studies for recruited patients; individuals with BMI ≥30 kg/m² were included in this research, whereas, Heshka et al.’s study included patients with BMI 27-40 kg/m². The RCT thus stopped at BMI =40 kg/m², while the current study includes patients with much higher BMIs, some with BMI of >50 kg/m².

A further interesting finding was that referred patients with hypertension and diabetes had a higher likelihood of turning up (37.6% and 36% respectively), compared with people without hypertension and without diabetes (30% and 30% respectively). It seems possible that this result is due to high blood pressure being an age-related problem and therefore as more older individuals turned up than younger ones; this creates the illusion of a highly significant effect. Another possible explanation, however, might be that a diagnosis of hypertension and diabetes heightened patients’ anxieties regarding their general health.

139 3.6.4 Completion rate

Some studies have used the higher threshold of 80% to define programme completion; this was consistent with the current research (Stubbs et al., 2011; Dixon et al., 2012).

Elsewhere, previous studies have applied a lower threshold and defined completed cases as participants who attended four or more appointments in 3 months, five or more sessions in 6 months, or six or more sessions in 12 months (McCombie et al., 2012); defining completers as those who attended at least half the sessions (Morrison et al., 2011; Logue et al., 2014). Studies using the current threshold for completion (80%) may lead to a more accurate reflection of the true effectiveness of weight management programmes when compared with studies that define completion as attendance of 50% of the sessions.

However, lower thresholds (around the 50% attendance rate) are a more realistic reflection of the median number of sessions attended by patients and therefore these studies using these lower thresholds include more patients when compared to studies using higher thresholds (80%) that then tend to focus on individuals that achieve higher weight losses.

80% is equivalent to the threshold of drug adherence used in the majority of medication trials as they wish to measure the effect of exposure to the full course of treatment; by using 80% attendance then it is ensuring exposure to the full course of behavioural treatment. The research results show a significant difference in completion rates between the sexes; men who completed the programme achieved their target weight loss. Stubbs et al. (2011) and Brown et al. (2015) reported completion rates of 57.4% in Slimming World and 55.2% in SLiM respectively among women (compared with 53.3% in the current research).

55.1% of the participants who attended at least 2 sessions completed the treatment programme. This research shows a low completion rate in younger participants and those in the most deprived quintile, which is consistent with the finding of a previous randomised trial (Heshka et al., 2003). In terms of comparing completion rate with other services, 56% of SLiM patients completed a 6 month course of treatment (Brown et al., 2015); and from the Lighten Up RCT at 3 months duration, 66%, 63% and 64% of participants completed the Weight Watchers, Sliming World or Rosemary Conley programmes (Jolly et al., 2011). Another study reported that out of 34,271 participants referred to Sliming World between 2004 and 2009, those who attended 12 sessions over a three-month period; totalled 58.1%, where programme completion was measured by attendance at minimum of 10 sessions out of 12 (Stubbs et al., 2011). In conclusion, the

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completion rate at GCWMS was low but consistent with other services; hence, this is a problem of all services and an area that needs further improvement.

3.6.5 Weight loss outcomes and comparison with other weight management