Reviewer ’s report  
 
Title: Associations between family factors and body weight gain from 20 years old  
 
Version: 0 Date: 22 Nov 2018  
 
Reviewer: Marshall Makate  
 
Reviewer's report:  
 
This paper evaluates the association between body weight gain and family -related factors among 
Japanese men and women aged 35 -79 years old. The paper tackles an important public health 
issue. Below are my comments that might improve the paper . 
 
Comments  
 My primary concern with this study is recall bias. I know the authors discuss a bit of this in 
the discussion. So, for instance, a participant who was aged 56 years at survey date would 
have been asked to recall her body weight when she was a ge 20 years (36 years ago)? This is 
somewhat problematic. Did the authors investigate any potential problems with this? 
Otherwise, the reported estimates could be very misleading.  
 
 On page 6, lines 19 -28, I do not see any action taken by the authors to l imit recall bias. They 
simply state that the Pearson's correlation was calculated and then what? Otherwise, what the 
authors are doing is an assessment, not "to limit". Limiting entails decisive action to address 
it, which I did not get from the authors' d escription. This issue needs to be carefully 
addressed or at least described appropriately.  
 
 How representative is the sample used in this study? Did any sampling weights applied to 
ensure representativeness?  
 
 On page 3, the description of the methods n eed to tell us more concerning the target area. 
Was the analysis based on data from a particular (single) region or multiple regions? I might 
have missed this, but I think its not clear from the description.  
 
 Did the authors control for other variables su ch as household or individual income that might 
influence weight gain or it was not collected?  
 
 The results reported in Tables 3 and 4, there is no mention of inclusion of controls for the 
survey year, region/city/place of residence. Are these controlled for in the analysis?  
 
 I think its still important to clearly define the outcome variable and mention unambiguously 
that it's binary.  
 
 The authors should also show the results for the overall model that combines both males and 
females and includes a dummy  indicator for gender (i.e. overall sample).  
 
 Given the possibility of recall bias as mentioned earlier, its important that the authors 
conduct a series of sensitivity checks. For example, do these results hold for specific regions 
in Japan; by educationa l level; or by city, rural/urban locality (if applicable)? The authors 
need to stratify the results by age groups as well.  
 
 On page 8, lines 28 -34, the interpretation of the results here is not clear. Certainly, an 
OR=1.00 neither implies an increase nor a decrease, and yet authors suggest "decrease and 
increase…". The authors must carefully check their interpretation of the results especially 
where they appear to suggest that an OR of 1.00 implies decrease...  
 
 Overall, the results interpretation needs a bit of improvement.  
 
 On page 13, lines 41 -47, this sentence needs rephrasing to clarify, it's not very clear.  
 
 General, the paper needs English language editing throughout to clarify points.  
Are the methods appropriate and well described?  
If not, please specify what is required in your com ments to the authors.  
 
Yes 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
No 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
 
Yes 
 
Are you able to assess any statistics in the manuscript or would you recommend an  
additional statistical review?  
If an additional statistical review is recommended, please specify what aspects require further  
assessment in your  comments to the editors.  
 
I am able to assess the statistics  
Quality of written English  
Please indicate the quality of language in the manuscript:  
 
Needs some language corrections before being published  
 
Declaration of competing interests  
Please complete a d eclaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, fees, funding, or salary from an  
organisation that may in any way gain or lose financially from the publication of this  
manu script, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that may in any way gain or lose  
financially from the publication of this manuscript, either now or in the future?  
 
3. Do you hold or are you currently applying for any patents relating to the content of the  
manuscript?  
 
4. Have you received reimbursements, fees, funding, or salary from an organization that 
holds  or has applied for patents relating to the content of the manuscript?  
 
5. Do you have any other financial competing interests?  
 
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have no competing interests' 
below.  If your reply is y es to any, please give details below.  
 
'I declare that I have no competing interests'  
 
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