This guideline was developed in accordance with the WHO evidence-informed guideline development procedures outlined in the WHO handbook for guideline development (20).
Advisory groups
Development of this guideline was undertaken by the WHO Department of Nutrition for Health and Development (NHD), in partnership with the members of the WHO Secretariat (Annex 2). The work was guided by the WHO Steering Committee for Nutrition Guideline Development (Annex 3), which provided overall supervision of the guideline development process. The WHO Secretariat and the Steering Committee included representatives from all departments of WHO with an interest in the provision of scientific advice on nutrition. Two additional groups were formed – a guideline development group and an external peer-review group – as outlined below.
Guideline development group
The guideline development group – entitled the WHO Nutrition Guidance Expert Advisory Group (NUGAG) Subgroup on Diet and Health – was convened to support the development of this guideline (Annex 4). This group included experts who had previously participated in various WHO expert consultations or were members of the WHO expert advisory panels, and others identified through open calls for experts. In forming this group, the WHO Secretariat took into consideration the need for a balanced gender mix, expertise from multiple disciplinary areas and representation from all WHO regions. Efforts were made to include subject-matter experts (e.g. in nutrition, epidemiology, paediatrics and physiology); experts in systematic review, programme evaluation and Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodologies; and representatives of potential stakeholders (e.g. programme managers, policy advisers and other health professionals involved in the health-care process). Representatives of commercial organizations were not invited to participate because the inclusion of such individuals is considered to be inappropriate for membership of any WHO guideline group because of actual, potential and perceived conflicts of interest. External resource persons – including subject-matter experts and systematic review and GRADE methodologists – were invited to the NUGAG meetings as observers to provide technical input and to present systematic reviews. These individuals did not participate in the decision-making processes. NUGAG's role was to advise WHO on the choice of outcomes important for decision-making, and on interpretation of the evidence for the development of recommendations.
External peer-review group
The WHO Secretariat selected, as external peer reviewers, representatives of public institutions that are members of the WHO Global Network of Institutions for Scientific Advice on Nutrition,1 subject-matter experts (including those in dentistry) and other stakeholders (including practitioners and editors of scientific journals). As with the selection process for the guideline development group, this external peer-review group was selected taking into account the need for geographical and gender balance, to provide diverse and representative perspectives. The external peer-review group was asked to review the draft guideline to identify any errors or missing information before finalization of the guideline. The external peer reviewers who provided comments on the draft guideline are listed in Annex 5.
Public consultation
A public consultation was held during the planning stages of guideline development. The consultation called for comments on the scope of the guideline and on the specific research questions to be addressed and outcomes to be investigated in the systematic literature reviews. A call for comments was also posted on the NHD website, and disseminated through the electronic mailing lists of NHD (>4000 addressees) and of the United Nations (UN) Standing Committee on Nutrition (also >4000 addressees).
Through this public consultation, 16 comments were received from various stakeholders, including representatives of government agencies, academic institutions, nongovernmental organizations (NGOs) and food industries. The comments were reviewed and assessed by the WHO Secretariat, and then presented for review – along with the WHO Secretariat's assessment – to the NUGAG Subgroup on Diet and Health.
Through a similar process, a public consultation was held to call for comments on the draft guideline before its finalization. A total of 173 comments were received, from representatives of 24 government agencies, two UN agencies, 52 NGOs, 54 industry organizations and associations, 31 academic institutions and 10 other interested individuals. These comments were also reviewed by the WHO Secretariat, and were assessed and considered when finalizing the guideline.
A list of people who submitted comments in response to the public consultations, summaries of their comments and the assessment of the received comments by the WHO Secretariat are available on the NHD website.2
Scoping of the guideline, evidence appraisal and decision-making
WHO developed an initial set of questions to be addressed in the guideline. The questions were based on the needs of Member States and international partners for policy and programme guidance. The population, intervention, comparison and outcome (PICO) format was used in generating the questions (Annex 6). The PICO questions were first discussed and reviewed by the WHO Secretariat and the WHO Steering Committee for Nutrition Guideline Development, and were then made available for public comment in February 2010. Feedback was received from a total of 16 individuals and organizational stakeholders, and the questions were adapted as necessary.
The draft set of PICO questions was presented to the NUGAG Subgroup on Diet and Health during its first meeting on 22–25 February 2010. During that meeting, the guideline topic was introduced, the scope of the guideline and the PICO questions were discussed, and outcomes and populations were ranked in importance by NUGAG members. The prioritization of the PICO questions defined the scope of the evidence to be used in informing development of the guideline. Subsequent to the meeting, WHO commissioned several systematic reviews and meta-analyses to address the PICO questions.
During the NUGAG meeting in February 2010, the anticipated difficulties in identifying sufficient data on weight gain, especially from developing countries, were discussed. To address this potential limitation, a number of NUGAG members from developing countries offered to share available country data. Additionally, to achieve systematic collection of “best available data and evidence” from developing countries, in August 2010 WHO sent out a call for data to all countries, through the WHO regional offices. Identified data were then reviewed and evaluated to determine whether they could be included in the review and analysis; no data met the inclusion criteria described in the PICO questions in Annex 6.
A follow-up meeting of the NUGAG Subgroup on Diet and Health was held on 14–17 March 2011, at which preliminary outcomes of the systematic reviews were discussed. At this follow-up meeting, NUGAG members requested further analyses, including the preparation of GRADE evidence profiles, which had not previously been included in the reviews. The NUGAG Subgroup on Diet and Health continued to review and discuss the evidence presented, and the GRADE assessment of the quality of evidence, at their subsequent meetings (held on 29 November – 2 December 2011, 27–30 March 2012 and 4–7 March 2013), and finalized the draft recommendations through consensus.
The systematic reviews and the GRADE evidence profiles for each of the critical outcomes were used for drafting the recommendations. When determining the strength of each recommendation, the NUGAG members considered various factors, including the overall quality of the evidence, the desirable and undesirable effects of the recommendation, values and preferences related to the recommendation in different settings, and the feasibility and cost of the options available to public health authorities in implementing the recommendation in different settings. These findings are summarized in Annex 7. The classification was discussed among the NUGAG members, the invited external resource persons and the members of the WHO Secretariat present at the meeting. The final wording of the recommendations and their strength were based on the consensus of members of the WHO Secretariat present and the NUGAG members only. There were no strong disagreements among the NUGAG members on any aspect of the guideline.
Management of conflicts of interest
According to the rules in the WHO Basic documents (37), all experts participating in WHO meetings must declare any interest relevant to the meeting before participating. Declaration of interest forms were reviewed by the WHO Secretariat in consultation with the WHO Legal Office when finalizing the composition of the NUGAG Subgroup on Diet and Health. In addition, each participant verbally declared his or her interests at the start of each meeting. The procedures for management of interests outlined in the WHO Guidelines for declaration of interests for WHO experts (38) were strictly followed. The potential interests declared by members of the NUGAG Subgroup on Diet and Health and experts who participated in NUGAG meetings as external resource persons are summarized in Annex 8.
Similarly, declaration of interest forms from external peer reviewers were assessed by the WHO Secretariat, and the summaries of those declared interests are also provided in Annex 8.
People who submitted comments in response to the public consultation were also asked to fill in the declaration of interest forms, so that the nature of their interests could be understood when reviewing and assessing their comments.
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NHD established the WHO Global Network of Institutions for Scientific Advice on Nutrition in 2010 to bring together the main public institutions that set guidelines for diet- and nutrition-related guidelines and guidance for their national governments, thus creating synergy and avoiding duplication of efforts (36).
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