| Study |
Bias |
| Randomisation process |
Deviations from intended interventions |
Missing outcome data |
Measurement of the outcome |
Selection of the reported results |
Overall |
| Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
| Tay 2014 |
Some concerns |
Randomization procedures (sequence generation and allocation concealment) were performed by research associates independent of outcome assessments and intervention delivery and was done "...using random varying block sizes before random computer‐generated assignment to either an LC or HC diet in a 1:1 ratio." Baseline characteristics were "...not significantly different between diet groups (p>0.05) in independent‐samples t‐test...or Chi2 test" |
Low risk of bias |
"....diet assignment was discernible by participants and interventionists". Deviations reported are expected to arise in usual care e.g. work commitments, unable to comply with diet, time constraints. A modified ITT analysis was conducted, all participants except those who dropped out or were lost to follow up were analysed in group to which they were assigned. |
High risk of bias |
18/64 (28%) participants in intervention group and 20/67 (30%) in the control group did not have data available.High attrition in both groups with reasons including inabilty to comply with diet, work commitments, health issues external to study and personal reasons. It is likely that with such high attrition, missingness is possible and likely to depend on the true value. |
High risk of bias |
Outcome reported under adverse events, no information about procedures used for ascertaining/reporting of adverse events. Constipation is subjective and participant‐reported, and participants were unblinded. The outcome, being participant‐reported, involves judgement, but there is no detailed information about how this adverse event was assessed. |
Some concerns |
No mention of pre‐specified data analysis plan, and trial registry does not mention the outcome and timepoint in any versions thereof. Analysis intentions are not reported in sufficient detail to enable an assessment. |
High risk of bias |
No specific information on allocation concealment provided. High attrition, with missingness possibly and likely related to true value. Subjective, participant‐reported outcome involving judgment, with no information on how the outcome was ascertained. Lack of information on pre‐registered methods. |
| Westman 2008 |
Some concerns |
"...participants were randomized to one of two treatment groups stratified upon BMI greater or less than 32 kg/m2 using a computer‐generated list, and invited to attend the baseline visit." No information describing allocation concealment. "There were no clinically significant differences between the treatment groups." |
Low risk of bias |
Participants received instructions, books and handouts about the diet they were to follow; "The delivery of the intervention and the assessment of outcomes were not blinded to the treatment assignment." Unclear whether an appropriate analysis was done; 10/48 (21%) in the intervention group and 3/49 (6%) in the control group discontinued the study, with no reasons for dropout or details about deviations from intended interventions provided (only that participants discontinued the diets). |
High risk of bias |
Outcome data not available for non‐completers in low carbohydrate diet group: 10/48 (21%) and in balanced diet group: 3/49 (6%). Differential attrition between groups, and high attrition in the intervention group; thus missingness could and is likely to depend on the true value. |
High risk of bias |
"participants completed an open‐ended side effects questionnaire. To enhance the description of side effects, participants completed a checklist of side effects commonly mentioned during weight loss studies at both the 20 and 24‐week visit. These two measures were combined to report the proportion in each group who experienced an adverse effect at any time during the study". Subjective assessment by unblinded participants; passive collection, however, use of same checklist and questionnaire in both groups. Constipation is subjective and participant‐reported, and participants were likely unblinded. The outcome, being participant‐reported, involves judgement This could be influenced by beliefs about the diet, but it is difficult to judge how likely this is. |
Some concerns |
No mention of a pre‐specified analysis plan. Outcome data never blinded. Analysis intentions are not reported in sufficient detail to enable an assessment. |
High risk of bias |
No specific information on allocation concealment provided. Differential and high attrition in the intervention arm, with no reasons. Subjective, participant‐reported outcome involving judgment, with no information on how the outcome was ascertained. Lack of information on pre‐registered methods. |
