| 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 |
| Bazzano 2014 |
Some concerns |
"We used a computer‐generated, blocked randomization, stratified by sex, to allocate participants to 1 of the 2 diet groups." No information on allocation concealment. "Demographic characteristics and cardiovascular risk factors were similar between groups." No formal hypothesis tests were reported, but baseline values in Table 1 showed no apparent imbalance. |
Low risk of bias |
"...dietitians were not blinded to the study hypothesis" No information about participant blinding, however, blinding of participants for these dietary interventions is highly unlikely. No reasons or details about deviations from intended interventions reported. "All analyses were conducted using the intention‐to‐treat principle" n=148 randomised and n=148 analysed. |
Low risk of bias |
16/75 (21.3%) participants in the intervention and 13/73 (17.8%) in the control group did not have data. "...performed sensitivity analyses to assess the robustness of our conclusions and departures from the MAR assumption." "Results of sensitivity analyses using multiple imputation techniques to impute missing values were consistent with those presented in our primary analyses" |
High risk of bias |
Reported under adverse events. "A range of adverse effects was assessed using closed‐ended questions at each counseling session." Constipation is subjective and participant‐reported, however, use of closed‐ended questions less likely to be applied differently across groups. "....all outcome assessors were blinded to the diet group assignment." Constipation is subjective and participant‐reported, and participants were likely unblinded. Participant‐reported outcome involving judgement; “mainstream”, overt and often distressing symptom; well‐known with low carb diets, thus likely to be influenced by knowledge of the intervention received. |
Some concerns |
"Study protocol and data set: Not available." 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. Constipation is a subjective outcome and was participant‐reported, likely by unblinded participants.The outcome involves judgement; is a “mainstream”, overt and often distressing symptom; well‐known with low carb diets, thus its reporting is likely to be influenced by knowledge of the intervention received. Lack of information in the pre‐registered methods. |
| Foster 2010 |
Some concerns |
"Using a random‐number generator, we randomly assigned participants within each site to treatment with either a low‐carbohydrate or low‐fat, calorie‐restricted diet for 2 years." No information on allocation concealment. No problematic differences observed between the two groups for baseline characteristics |
Low risk of bias |
Masking none; open‐label. Deviations reported are expected to arise in usual care e.g. relocated, dissatisfied with the program, pregnancy. Modified ITT; participants with missing data excluded. |
Low risk of bias |
25/153 (16%) participants in the intervention group and 19/154 (12%) in the control group did not have data. Analysis approach for constipation specifically not well reported, but assume similar approach as with other outcomes ("..longitudinal models implemented for this study relax this missing‐completely‐at‐random assumption in various ways." "Under the sensitivity analysis based on imputing missing outcomes with the highest (13.795) and lowest (‐18.355) random‐effects slopes (that is, change in weight per month) under the mixed‐effects model for weight, our qualitative findings were not sensitive to either imputation approach."). |
High risk of bias |
"We assessed general symptoms with a symptom checklist used in previous weight‐loss studies (17). The checklist contains 26 symptoms rated as none, mild, moderate, or severe. Symptoms were categorized as either absent (none) or present (mild, moderate, or severe because the symptom data were not normally distributed (most symptoms were listed as none or mild)." No evidence that a different method was used across intervention groups to measure weight. Use of a checklist and Likert scale less likely to be applied differently across groups, however, constipation is subjective and participant‐reported. Masking none; open‐label. Participant‐reported outcome involving judgement; “mainstream”, overt and often distressing symptom; well‐known with low carb diets, thus likely to be influenced by knowledge of the intervention received. |
Some concerns |
No mention of pre‐specified analysis plan; trial registry at date prior to study publication does not mention outcome or timepoint. Analysis intentions are not reported in sufficient detail to enable an assessment. |
High risk of bias |
No specific information on allocation concealment. Constipation is a subjective outcome and was participant‐reported, by unblinded participants.The outcome involves judgement; is a “mainstream”, overt and often distressing symptom; well‐known with low carb diets, thus its reporting is likely to be influenced by knowledge of the intervention received. Lack of information in the pre‐registered methods. |
| Liu 2013 |
Low risk of bias |
No information about sequence generation. "Randomisation was conducted by a statistician who was not involved in any other aspects of the study by using block randomisation, stratified by 10‐year age categories." "Although the participants were randomised by age, baseline BMI levels of the two groups were similar after randomisation." |
Low risk of bias |
No information, however, blinding of participants and people delivering these dietary interventions is highly unlikely. Deviations reported are expected to arise in usual care e.g. busy schedule or for personal reasons. Modified ITT, one drop‐out due to busy schedule excluded in control group. |
Low risk of bias |
1/25 (4%) in the intervention group and 1/25 (4%) in the control group did not have data. |
High risk of bias |
Reported under adverse events; "...participants were asked to report any side‐effects or discomfort to the dietitian". Subjective assessment by unblinded participants; passive collection with open‐ended approach that could be applied differently across groups. |
Some concerns |
No mention of pre‐specified data analysis plan; and trial registry at date prior to study publication does not mention the outcome and timepoint. Analysis intentions are not reported in sufficient detail to enable an assessment. |
High risk of bias |
Outcome is subjective and was assessed by unblinded participants through passive collection with an open‐ended approach. Lack of information in the pre‐registered methods. |
| Mateo‐Gallego 2017 |
Some concerns |
"We carried out the randomization process by generating a number sequence (including 93 correlative numbers because this was the number of subjects we planned to randomize) in the following webpage: https://www.random.org. The number for each participant was correlatively assigned (e.g; the first randomized women was assigned with number 1)" (from author correspondence). No information about allocation concealment. "There were no significant between‐group differences at baseline." |
Low risk of bias |
"Participants were blinded to their assigned macronutrient composition. The dietician who formulated the diets and carried out the individual consultations was aware of each participant's group assignment, but the rest of the staff was blinded to that information." "...single‐blind study". Deviations reported are expected to arise in usual care e.g. lost to follow‐up, personal reasons. ITT (appears that number randomised = number analysed). |
Low risk of bias |
The number of participants who were randomised were also analysed. |
Some concerns |
Reported under adverse events; no information about procedures used for reporting of adverse events. "Participants were blinded to their assigned macronutrient composition. The dietician who formulated the diets and carried out the individual consultations was aware of each participant's group assignment, but the rest of the staff was blinded to that information." |
Some concerns |
No mention of pre‐specified data analysis plan, and trial registry at date prior to study publication does not mention the outcome and timepoint. Analysis intentions are not reported in sufficient detail to enable an assessment. |
Some concerns |
No specific information on allocation concealment. Very little information on how the outcome was assessed or by whom, but participants and all staff other than the dietician (who formulated the diets and conducted the individual consultations) were reportedly blinded. Lack of information in the pre‐registered methods. |
