Participants were followed up at 6 months between January 2010 and July 2010 and at 12 months between July 2010 and January 2011. Participant flow through the trial is shown in .
Flow of participants through the trial.
We recruited 381 participants with a median age of 48.5 (IQR 37.5–60.4), weighing 60.1–152.2 kg, with waist circumference of 76–147 cm. The majority (72%) were women, 12% (47/381) had diagnosed diabetes, 1.3% (5/381) were on antipsychotic medication, 60% were in employment, 47% were university graduates and 73% described their ethnicity as Caucasian (). Participants wanted to lose an average of 18 kg (SD =12.4), representing 16.7% of their baseline weight. There were no significant differences between groups for any of these variables.
Baseline characteristics of participants wishing to lose weight allocated to usual care (control) or to the CAMWEL programme (intervention)
Measurements were obtained for 69% (n=263) of the sample at 6 months and 57% (n=217) at 12 months. There were no significant differences in follow-up rate at 12 months by randomisation group (60.0% control, 53.9% intervention, p=0.23), but those followed up tended to be older, have lower BMI, fat mass and per cent body fat, and were less likely to be from a deprived area than those not followed up ().
Comparison of baseline characteristics of participants followed up at 12 months and those lost to follow-up (mean (SE) unless otherwise stated)
Based on the intention-to-treat analysis using imputed missing values (), at 12-month follow-up, structured support resulted in a mean difference in weight loss between the two groups of −0.70 (−2.71 to 0.76) kg. A higher proportion of participants lost 5% or more of their baseline weight in the intervention (32.7%, 95% CI 24.9% to 40.5%) when compared with the usual care (20.4%, 95% CI 13.3% to 27.5%) group (OR 1.80 (1.02 to 3.18, p=0.04).
Changes in outcomes at 6 and 12 months and treatment differences between participants wishing to lose weight allocated to a structured one-to-one weight loss programme (intervention) or to usual care (control)
The intervention programme was also associated with weak evidence of beneficial trends in waist circumference, per cent body fat and per cent weight change. Heart rate was reduced by 3.7 (0.3 to 7.0, p=0.03) beats per minute in the intervention group compared with the control group.
Based on data for participants who completed the 12-month follow-up (), a higher proportion (one in three compared to one in five) in the intervention group had lost at least 5% of their initial weight (difference 14.7% (3.0 to 26.4, p=0.01)) and experienced a greater average reduction in waist circumference (difference 1.88 cm (0.01 to 3.76, p=0.05)) compared with those in the control group. Weak evidence of reductions in weight, per cent body fat, BMI, blood pressure and heart rate were observed in the intervention group compared with the control group. The absolute risk reduction for losing 5% baseline weight was 14.7% (3.0 to 26.4), and the number needed to treat was 6.8 (3.8 to 33.2). A higher proportion of those in the intervention group (84%, 21/25) who had lost ≥5% at 6 months had managed to keep this level of weight loss at 12 months compared with those in the control group (61.5%, 8/13). We were unable to identify characteristics of the subgroup of participants more likely to lose 5% of their baseline weight.
No evidence of differences was found between the two groups on any of the psychological or quality-of-life measures.
Participants in the intervention group were more satisfied than those in the control group with the level of weight loss achieved and they found participation in the trial and feedback of physical measurements helpful (). The intervention group also reported receiving more patient-centred care than those in the control group as measured by the Patient Assessment of Care for Chronic Conditions scales (). Detailed analysis of the interviews and focus groups with a subset of the participants will be reported elsewhere.
Participant satisfaction with care received by allocation group at 12 months
Participant assessment of care received by allocation group at 12 months
The intervention programme
The majority of participants (38/56, 67.9%) reported that a regular meeting with the advisor was the most helpful aspect of the programme and the least helpful was the use of handouts in improving eating habits (17/56, 30.3%). The majority (84%) said they would choose to continue to meet an advisor beyond the 12 months of the current study, with most (73%) preferring to see the advisor at least every 4 weeks.
Behaviours associated with losing 5% or more of baseline weight
Participants who lost 5% or more of their baseline weight were more likely to state that they had reduced their fat and sugar intake in the previous 6 months than those who did not; there was no evidence of increasing levels of physical activity between the groups (). They also reported that attending regular meetings with a non-judgemental advisor, discussion on portion sizes and use of the pedometer were particularly useful and that they would continue to monitor food intake to maintain their weight.
Reported changes* in eating and activity habits by participants who lost 5% or more of baseline weight compared with those who did not
Thirty-eight participants were known to have been prescribed drugs for weight loss or to have undergone weight loss surgery during the trial period. Of these, 27 were followed up at 12 months (12 control: mean weight change −2.44 kg (−7.15 to 2.27); 15 intervention: mean weight change −3.51 kg (−6.95 to −0.08)). The difference between groups was 1.07 kg (−4.32 to 6.46, p=0.69). In analysis excluding these participants, those in the intervention group showed significantly greater reductions in weight (1.72 kg (0.29 to 3.14, p=0.02)), waist circumference (2.52 cm (0.32 to 4.72, p=0.03)), BMI (0.63 kg/m2 (0.11 to 1.14, p=0.02)) and per cent baseline weight loss (1.94% (0.32 to 3.56, p=0.02)) when compared with the control group at 12 months. In addition, a higher proportion of participants in the advisor group lost ≥5% of their baseline weight when compared with the control group (OR 2.68 (1.13 to 5.70, p=0.03)).
The number of sessions attended was available for 87 participants of whom 40 (46%) attended more than 70% (10/14) of the available sessions. Half (50%) of the participants attending more than 70% of the programme lost 5% or more of their baseline weight compared with a quarter (23%) who attended fewer sessions (difference 26.5%, 95% CI 6.9 to 46.3, p=0.01).