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Analysis Science and Politics of Nutrition

Role of government policy in nutrition—barriers to and opportunities for healthier eating

BMJ 2018; 361 doi: (Published 13 June 2018) Cite this as: BMJ 2018;361:k2426

Food for thought

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  1. Dariush Mozaffarian, dean1,
  2. Sonia Y Angell, deputy commissioner2,
  3. Tim Lang, professor3,
  4. Juan A Rivera, director4
  1. 1Friedman School of Nutrition Science and Policy, Tufts University, Boston MA, USA
  2. 2New York City Department of Health and Mental Hygiene, New York City NY, USA
  3. 3School of Arts and Social Sciences, City University of London, UK
  4. 4Instituto Nacional de Salud Pública, Mexico City, Mexico
  1. Correspondence to: D Mozaffarian dariush.mozaffarian{at}

Dariush Mozaffarian and colleagues review strategies governments can use to improve nutrition and health

For most of human history including much of the 20th century, insufficient food was the greatest nutritional challenge. To tackle this, government sought to stimulate the production and distribution of as much inexpensive food as possible, in particular starchy (high carbohydrate) staple commodities and their shelf stable processed products. At the time, a global pandemic of obesity and chronic diseases from the widespread availability of inexpensive, unhealthy food was inconceivable.

The relatively recent rise of diet related chronic diseases including obesity, type 2 diabetes, cardiovascular diseases, and several cancers is at least partly a byproduct of these historical approaches and the responses of industry and consumers. A separate article in this series reviews the trends in nutrition science over this period,1 which have slowly shifted focus from undernutrition defined by calories and micronutrient deficiency to food based diet patterns and overall health effects of the food supply.

Even with the unprecedented rise in diet related chronic diseases, government policies have continued to emphasise agricultural production of staple commodities and support for the food industry motivated by conventional perspectives on food security, economics, and trade. While undernutrition has improved with government supported systems changes such as agricultural development and fortification programmes,1 government has tended to use educational policy measures directed at individuals in response to the rise in chronic diseases. Such measures aim to influence diet quality by emphasising personal responsibility and choice through dietary guidelines, food labels, menu labelling, and clinical counselling.

Growing evidence makes clear that multiple, complex factors beyond personal decisions strongly influence dietary choices and patterns (fig 1).234567 Even at the individual level, dietary habits are determined by personal preference and also age, gender, culture, education, income, health status, and nutritional and cooking knowledge and skills.8 Psychological influences include attitudes to food and health, incentives, motivation, and values.9 Food preferences may also be influenced by early life exposures, including the mother’s diet during pregnancy, infant feeding practices, and foods consumed in early childhood.101112 Broader sociocultural determinants of personal choices include household lifestyle patterns such as television watching and sleep,13141516 family and community norms, social pressures, social class, social networks, and race/ethnicity.17 The local environment also plays an important role.234567

Fig 1
Fig 1

Multilayered influences beyond personal knowledge and preference alter food choices. Government can consider these influences as potential targets, barriers, facilitators, and effect modifiers of food policies. Reproduced with permission from Ashfin et al2

Importantly, wider commercial pressures also affect consumer choice, including food packaging, marketing, advertising, and sociocultural perceptions of norms, status, and prestige.181920 Each of these individual determinants is shaped by, and in turn shapes, much broader drivers of food choice such as food industry formulations and globalisation, farming policy and production practices, national and international trade agreements, and ecosystem influences.2122

Uncoordinated, these many influences are powerful and are nearly insurmountable barriers to making healthy dietary choices for many people worldwide. They can introduce health inequities, and sustain or deepen existing ones. However, with thoughtful, evidence informed policy, each of these factors also provides an opportunity for governments to support improvements in diets, health, wellbeing, and equity.

Based on advances in behavioural and policy science, we review strategies and approaches that governments can use to directly improve nutrition. We appreciate that other nutrition policy frameworks have been considered.567 We focus on a broad range of interventions and nutrition policies and discuss their strengths, limitations, uncertainties, and recommendations.

Types of policy interventions

Governments can use a spectrum of policies from voluntary to mandatory. These include a bill (proposed law), law/act/statute (approved by legislative and executive branches), agency implementation (interpretation, application, regulation), court decision, guideline (recommendation, not mandatory), or directive (internal to an institution).

By their nature, public health concerns such as nutrition are multifactorial. Even single or simple interventions induce effects within complex webs of interactions.23 We focus on policies directly targeting nutrition rather than more indirect mechanisms related to, for example, trade, farming, food waste, general education, and economic empowerment. Each policy strategy can be classified according to different related characteristics (box 1) that need to be considered and defined in government policy design.24

Box 1

Classification of policy interventions

  • Levelcity, state, or national government; international agencies; organisations (eg, school, worksite, healthcare facility); local neighbourhoods and communities

  • Target—consumer, organisation (eg, school, worksite), health system, production (farming, agriculture), industry (manufacturer, retailer, restaurant)

  • Domain—population education (eg, dietary guidelines, mass media), point-of-purchase information, fiscal policies, food quality standards, built environment changes, research and innovation

  • Mechanism—altering consumer preferences or choice, food formulations, or food availability and accessibility


Government food policy strategies

For the different government policy actions, we present a summary of their strengths, limitations, uncertainties, and recommendations (table 1). Implementation of policy actions must be accompanied by systematic surveillance and evaluation to assess progress and guide further efforts.

Table 1

Key government related food policy strategies to improve diet quality*

View this table:

Some key findings can be highlighted. For example, population education and point-of-purchase labelling are widely and increasingly used. Such “soft” policies place most responsibility on the individual consumer, with which industry is often more comfortable. The effectiveness of such policies on behaviour change overall and in specific population subgroups has been variable and they may have smaller effects in marginalised groups.3347980 However, such approaches can also promote industry reformulations, which may have an important effect on longer term health beyond immediate consumer behaviour.34 Overall, such approaches can be valuable as part of a broader, multicomponent government food and nutrition strategy.

In contrast to education and information, fiscal incentives and disincentives aimed at consumers, producers, and retailers have more consistent evidence of effectiveness.234567 Disincentives can include excise or sales taxes on unhealthy items such as sugar sweetened beverages and junk food383940 or removal of industry tax benefits for development and marketing of unhealthy products. Disincentives on specific foods can be politically difficult, however, the rapid international expansion of taxes on sugar sweetened beverages shows the growing acceptance of this approach.81 Such taxes can be financially regressive for lower income individuals, but progressive because of benefits to nutrition and health. To reduce financial regressivity and increase the health effect, tax revenues can be used for other health promotion strategies including retail, manufacturing, or agricultural incentives to reduce the price of healthier food products.4142 Rather than being punitive, economic incentives and disincentives “normalise” the market by partly bringing the prices of different foods closer to their true societal cost.

Procurement and quality standards are relatively sustainable, low cost strategies for government to implement. For instance, limitations or standards on trans fat and sodium have been implemented in many countries and similar standards being considered for free or added sugars.234567 Because governments are often one of the largest buyers of food, nutrition procurement standards should be set for all their food purchases across agencies and programsmes.82 In addition, vanguard local and national quality standards should be implemented on the use of food additives by industry such as trans fat, sodium, and sugar.454647838485

Schools and worksites are natural and complementary settings for effective nutrition policies.234567 In schools, after school, and early childcare programmes, government should promote nutrition standards for both onsite meals and competitive foods as low cost, sustainable interventions—examples include standards in the US, Canada, Mexico, Europe, and New Zealand.49 Free or low price provision of fruits and vegetables, farm to school programmes, and school gardens are also promising strategies, although long term effects and cost-benefits are not yet rigorously evaluated. Worksite wellness programmes can not only improve health but also lower costs and increase productivity. In one analysis, every $1 spent on worksite wellness programming was estimated to generate about $3.27 in lower medical costs and $2.73 in less absenteeism.55 However, relatively few long term worksite studies have evaluated the effects on diet, few rigorous cost effectiveness data are available, and increased employee turnover reduces the immediate incentives to businesses to invest in the health of their employees.34 Governments should invest in their own employee worksite wellness programming and pursue policies, such as guidelines and tax incentives, to promote the implementation and evaluation by private employers of worksite efforts for healthier eating.

Ironically, one of the least used settings to promote better nutrition is the healthcare system. Individual providers and health organisations face several barriers to nutrition promotion. To overcome these difficulties, governments should promote policies that support implementation of evidence informed actions within the healthcare system and with relevant partners such as community health workers, pharmacies, and other community based organisations. Useful strategies include multidisciplinary lifestyle programmes for conditions such as prediabetes,56 medically tailored meals for patients with complex chronic diseases,5758 prescriptions for fruit and vegetables for health promotion and disease prevention,59 and nutrition counselling during pregnancy and early childhood. Other important actions include: educating healthcare providers on food and nutrition, systematically introduced through national reform of medical and specialty licensing exams and continuing medical education; expansion of nutrition counselling services through new reimbursement strategies and task sharing with community partners; and inclusion of standardised clinic and mobile assessments of diet quality and food insecurity in electronic health records, which are needed to assess and integrate nutrition into treatment plans, evaluate new health system interventions, and inform performance and reimbursement systems.2606162 Expanding access to care through universal coverage or other national strategies can further increase the effect of nutrition policies on health. Hospitals should be incentivised by new quality measures and reimbursement guidelines to implement worksite wellness and engage in community public health.63646566

Standards for marketing, such as limiting advertising to children of foods and beverages that do not comply with basic nutrition, are recommended by the World Health Organization and Institute of Medicine.676869 Several countries currently implement different forms of marketing restrictions: for example, Chile has recently limited advertising and use of cartoon characters to market products to children that do not meet standards for added sugar, added saturated fats, and sodium.70

The media and policy makers have increasingly focused on the local food environment, such as clustering of fast food sellers around schools71 and absence of supermarkets in many neighbourhoods (termed “food deserts”).72 However, the actual cause and effect of many of the observed cross sectional relationships and the appropriate ways to characterise the complex facets of availability and accessibility are poorly characterised.23456773 Further investigation including implementation and evaluation research is needed to allow the development of more concrete recommendations on how to improve the local food environment.

Modern nutritional science is young, especially in relation to the risk of the main chronic diseases.186 Strong government funding for basic nutrition and applied research and innovation is essential to continue to develop evidence based priorities for dietary policies. Areas for investigation in the next decade, for example, include basic molecular pathways; diet-microbiome-host interactions; individual fatty acids and their lipid derivatives; prebiotics, probiotics, and fermentation; phenols and other bioactive compounds; personalised nutrition; and nutrition data (“big data”). Government funding should also make applied research a priority, including new technologies for nutritional assessment and behaviour change, and policy implementation and evaluation.

Governments should also promote the food industry’s shift towards healthier foods, taking advantage of rapidly rising consumer demand. Tax incentives and other fiscal policies should promote research, development and marketing of healthier foods in the food industry, combined with (and potentially funded by) fiscal disincentives for marketing and promoting sugar sweetened beverages and junk foods. A programme of government funding and transparent public-private partnerships for nutrition research is also needed to help minimise conflicts of interest and perceived and real biases.8687

No single intervention can tackle the complexities of the current food system, and different approaches can be complementary and synergistic.234567 For example, trade policy traditionally emphasises foreign direct investment, trade liberalisation, and privatisation to encourage private sector investment but the influence of such actions on the food environment can also have positive and negative effects on health.757677 These interconnections support the importance of an integrated, government strategy that uses and adapts existing structures and systems. Ideally, actions should be coordinated between ministries, agencies, and at local, national, and international levels. Upstream agricultural, trade, research, and industry measures can be integrated with midstream school, worksite, healthcare, and other environmental approaches as well as downstream consumer efforts. Such a “nutrition and health in all” policies could greatly improve food systems and health, national productivity, equity, and health savings. Strong government leadership is essential to help deliver such a comprehensive, sustained, multitarget, and multilevel approach.78

Translation of evidence to policy action: needs and difficulties

Local and national governments have important roles in bringing healthier food and food security to their populations. However, the path from knowledge to effective action requires capacity in several areas. To our knowledge no country has implemented a full range of updated, comprehensive, and evidence informed strategies to encourage a healthier and more equitable food system (table 1). Given the remarkable health and economic burden of diet related illness and the need for multistakeholder solutions, a coordinated national food and nutrition policy strategy should be a priority for all governments.

Government must have appropriate knowledge to translate evidence into policy action. This includes an evidence based assessment of what defines a healthy diet; an understanding of diet related health and risk distributions overall and in at-risk subpopulations; analyses of how poor diet affects non-health sectors such as private businesses or the military; and consideration of environmental and societal values such as sustainability, equity, and justice. Insufficient awareness of policy makers of these factors can be compounded by evolving science and conflicting media messages. For example, some policy strategies continue to emphasise reduction in total fat, total saturated fat, or total calories, rather than food type and quality, processing methods, additives, and diet patterns.18889New metrics are needed that allow the healthiness of food products to be compared on multiple nutrient criteria.37 In addition, tackling obesity is sometimes seen as the only goal of nutrition policy and programming, rather than improved diet quality and overall health and wellbeing. The evidence to support policy interventions is also different from that for interventions delivered to individuals.234567 Interventions on high risk individuals can often be studied in randomised placebo controlled trials; in contrast, policy interventions on populations often cannot. Thus, predictive modelling, observational, quasi-experimental, and interventional studies, and surveillance data must feature more heavily in the standards of evidence required for policy change.

Government must have the capacity to intervene. This includes having an evidence informed plan, access to technical experts for implementation and evaluation, and adequate resources and authority to act in the required areas. For many governments, developing a comprehensive nutritional policy will be new and unfamiliar, and require acknowledgement of certain limitations of the current system. The expertise to combine and phase different policy approaches can be lacking. Jurisdiction and funding for different aspects of policies may be spread across government sectors and ministries, which may share unequally the costs and benefits. Budgets for technical policy work on nutrition are often tied to resources allocated for the prevention of chronic diseases, which is underfinanced given their health and economic burden. Surveillance systems for monitoring and evaluating nutrition trends and disparities are under resourced. For some promising policy actions, relevant data demonstrating the links between food policies and health, healthcare costs, disparities, and economic problems are often unavailable to policy makers at the right time or in the right format for policy action.

Government must have the will to act and the governance and partnerships to support action. This requires support from civil society and relevant private and other non-government actors to implement and sustain appropriate policies. Political willingness to act can be undermined by several factors. For example, factors driving government food production policy (eg, employment, short term business profits, and international competition) may be different from those driving nutrition policy (eg, health and healthcare costs). Although dietary shifts can have rapid effects on health,90919293 the perception that dietary interventions require long periods to achieve benefits may not coincide with political and budget cycles. Public opinion may also not support policies seen as intrusive.94 Identified dietary priorities may not match public priorities and sentiment, nor agency authority for action. Industry opposition can be a major barrier, including political lobbying and marketing campaigns to fight policies they consider unfavourable.95 When policies are passed, lack of implementation because of limited resources, management, and accountability can greatly limit their effect,96 as in the case of school food standards in Mexico or quality standards to limit industrial trans fats in India.

Other stakeholders

Other stakeholders should promote, facilitate, and complement government policy efforts.25219798. Academia should prioritise research on optimal dietary targets and cost effective policies; monitor and evaluate health indicators and policy outcomes; engage with communities, advocacy groups, the media, business, and policy makers; and inform and evaluate government and industry efforts. Health systems, clinicians, and insurers should implement strategies on patient behaviour change; advocate for broad changes in health systems to support these efforts; and engage with local communities. Employers, communities, schools, hospitals, and religious congregations should implement organisational strategies for healthier eating. Advocacy groups should partner with scientists to disseminate best practices and hold government and industry accountable for meaningful action.

Large multinational companies frequently have a great influence because of their economic power, government lobbying, and communication and marketing resources. Unclear or variably enforced government provisions on conflicts of interest can further increase industry influence. More directly, certain food companies have actively opposed policies about healthier foods,95 especially in low and middle income countries.96 Because multiple actors must be involved in effective nutrition policies and programmes, transparent rules of engagement are needed for public-private interactions (box 2). The food industry must be a facilitator for, not a barrier to, healthy food policies and use their expertise, scale, innovation, and marketing to develop, distribute, and market healthier foods, and create transparent, sincere partnerships with academics, advocacy groups, and government. 87100101 To achieve this, the food industry’s ultimate success ought to be linked to the distribution of healthy, optimally processed foods in a sustainable, equitable, and profitable way.

Box 2

Lessons from interactions between public and private stakeholders in food and nutrition

Engagement with multiple actors is essential for the implementation of effective policies and programmes to tackle obesity and other chronic diseases. Clear rules are needed to manage conflicts of interest.

A recent report of the UK Health Forum analysed examples of international public-private interactions for food and nutrition policies for the prevention of chronic diseases.99 The report sheds light on relationships between government, civil society, academia, and the food and beverage industry and the need to strengthen governance for the identification and management of conflicts of interest that may arise.100 While the cases vary in their geographical and sociopolitical contexts and objectives, common themes are seen:

  • Interactions between public and commercial sectors are numerous and diverse

  • Transparency and documentation of these interactions are often limited

  • Corresponding risks are neither assessed nor managed before or during such public-private interactions.

In Mexico a multistakeholder effort to monitor, evaluate and provide feedback on policies for the prevention and control of obesity and diabetes101 showed that providing the commercial sector privileged access over public health and civil society led to biased conclusions influenced by commercial interests. Other cases in Chile, Brazil, Mexico, Fiji, Canada, Spain, and England show that conflicts of interest can undermine effective policy. Many examples exist of companies that produce sugar sweetened beverages and junk food putting up strong resistance and lobbying to counter national policy actions for obesity prevention. These include shifting the blame for obesity and chronic diseases away from specific products and towards physical inactivity and energy balance, and the use of multistakeholder coalitions to shape policy that benefits commercial interests. In Fiji and other countries industry self regulation was not effective and was used by the food industry to rebut government efforts to implement recommended public health policies.102

Specific lessons learnt about public-private interactions for policy and practice include:

  • Need for governance principles in multistakeholder platforms. Governments have a duty to ensure that interests not in the public good do not influence the individuals or institutions responsible for public decision making, and preserving integrity and public trust. Multistakeholder platforms should have guidelines on conflict of interest identification, management, and protection. Governments should establish guidelines about participants in groups that are responsible for policy design. Otherwise, such platforms may stall regulation and policy by suggesting agreement among civil society, government, and industry when there are in fact disagreements.101103

  • Need for regulations on lobbying. Lobbying strategies can greatly affect health policy decisions.104 In many countries, lobbying activities and corporate financing of politicians and political parties are loosely regulated. Strong regulations on transparency and activities are needed to maintain effective, unbiased policy making.

  • Need for standards on public-private partnership. Given widespread recommendations for public-private alliances and partnerships to support the achievement of global health and development goals, governance of public-private partnerships is important to ensure that efforts to improve food and nutrition are in line with ethical, transparency, and accountability principles. For instance, the food and beverage industry should not participate in decision making on the design, implementation, or evaluation of obesity prevention policies. Their voice should be heard but decisions should be made by those without commercial interests.

  • Need for more than self regulation. Industry self regulation is not sufficient to advance public health goals. Additional government regulation and standards are important to enforce the implementation of health related food and nutrition policies.

The case studies also highlight the need for scientific evidence free of conflicts of interest. Particularly in the cases of sugar sweetened beverages and junk foods, commissioning studies with strong ties to or funding from the food and beverage industry is a risk.105 Independent, peer reviewed scientific research is important to help inform policy making with the best available evidence. When industry does play a role in research studies, the involvement should be transparent.

Analysis of these case studies indicates a need to address conflict of interest and industry influence in health and nutrition policy making. WHO recently published draft guidance for the prevention and management of conflicts of interest in policy development and implementation of national nutrition programmes.106 Governments, academia and civil society all play an important role. In addition, further research is needed on how to identify, study, and minimise conflicts of interest in food and nutrition policy.


Given the scale of the problem and the multinational nature of the food industry, global public health efforts can complement national and local government activities. International economic and political institutions, including the World Bank, United Nations, and World Trade Organisation, must play a more assertive role. Actions should include developing and measuring adherence to nutrition policy standards; coordinating efforts of member country; assisting governments as needed with design, implementation, and evaluation of food policies; bringing stakeholders together including global agribusiness, restaurant chains, and food manufacturers; and providing a countervailing force to multi-national food industry lobbying.

Conclusions and recommendations

Because multisectoral approaches are necessary to create healthier food systems,5 governments should actively develop and implement policies to promote strategic and sustained change. We recommend several specific government roles and actions (box 3). For each, governments should assess whether the implemented strategies have the intended effects, identify and tackle disparities, and detect unintended consequences. This information should be made accessible to the public, academia, and other organisations.

Box 3

Recommended government roles and actions for a healthier food system

  • Recognise that good nutrition is a priority for local, national, and global health, equity, and economic security

  • Acknowledge the importance of multilevel approaches, not “magic bullets”, in order to implement strategic, coordinated government action. Based on current evidence, the best approaches are:

    • Fiscal incentives/disincentives (eg, taxes and subsidies) for consumers, the food industry, and organisations (eg, worksites)

    • Prioritisation of both food security and nutritional quality in food assistance programmes

    • Appropriate standards for additives including trans fat, sodium, and added sugars

    • Procurement standards for all government food purchases and venues including food assistance programmes

    • Use of schools and worksites to promote healthier eating

    • Incorporation of food and nutrition into the healthcare system at all levels

    • Nutrition standards for marketing of foods and beverages to children

    • Front-of-pack labelling of evidence informed metrics such as overall fat quality (eg, unsaturated to saturated fat ratio), carbohydrate quality (eg, carbohydrate to fibre ratio), and sodium

  • Implement policies using the best available evidence, which also provides an opportunity to build further evidence for better decision making by evaluation of the policies being implemented

  • Emphasise strategies with the greatest potential to reduce social and racial/ethnic disparities from clustering of suboptimal diet habits, local environments, and disease risk factors

  • Increase support for food and nutrition research to ensure that both dietary targets and policy efforts are scientifically sound

  • Support public-private partnerships with the food industry and other major non-food businesses (eg, private health and life insurance, and self insured corporations) for research and development on healthier products, effective behaviour change, and other common aims. This must include development of clear and transparent policies to identify and minimise conflicts of interest (see box 2)

  • Facilitate participation of other stakeholders in policy development, implementation, and evaluation

  • Incorporate nutrition and health in all of government, for example, city planning, economic development, agricultural and trade policies, and nutrition impact assessment

  • Link nutrition and food policies to economic and production indices such as the influence of diet related illness and health on production and the economy

  • Create a ministerial or cabinet leadership position with oversight and budgetary authority for cross agency food and nutrition policy

  • Support monitoring and evaluation of nutrition habits, food systems, and corresponding policies including for individuals, communities, and larger systems. Link to and use existing surveillance systems (eg, healthcare) as well as new technologies (eg, social media, and personal monitors)

  • Identify and use complementary global public health activities (eg, the United Nations Sustainable Development Goals), including to bring stakeholders together and, where necessary, counter the food industry


The development and implementation of effective nutrition policies by governments have been hindered in the past by several factors, including insufficient knowledge, capacity, and will. Action and advocacy by many stakeholders are needed to overcome these barriers. Past successes that can point the way forward include effective public health approaches to complex problems such as tobacco use, motor vehicle crashes, and occupational safety. These have been achieved through a combination of scientific progress, public awareness and advocacy, consumer demand, industry innovation, government regulation, and cultural change. These successes provide a template for a healthier food system, that is: address the consumer, the product (agricultural commodities, foods, and beverages), the environment (retailers, cafeterias, and restaurants), and the culture (unhealthy eating, and marketing). To be successful, broad alliances are often required to maintain pressure, provide sound data, and bring about the desire for progress. Strong government policy is crucial to achieve a healthy, profitable, equitable, and sustainable food system that benefits all.

Key messages

  • Despite the rise in diet related chronic diseases and associated costs, government policies continue to have conventional perspectives on agricultural production, industry support, food security, economics, and trade

  • New, evidence informed government nutrition policies are needed to reduce the risk of chronic diseases and reduce dietary and health inequities

  • The complementary and synergistic nature of different policies supports the need for an integrated, multicomponent government strategy that uses and adapts existing structures and systems

  • To translate evidence into action, governments must have the appropriate knowledge, capacity, and will to act and the governance and partnership to support action

  • Specific actions by major stakeholders should promote, facilitate, and complement policy efforts

  • Strong government policy is essential to help achieve a healthy, profitable, equitable and sustainable food system that benefits all


  • Contributors and sources: DM conceived the paper and is the guarantor. All authors contributed to drafting the manuscript and critical revision of the manuscript for important intellectual content, and approved the final manuscript. The authors selected the literature for inclusion in this manuscript based on their own expertise and knowledge, discussions with colleagues, and editorial and reviewer comments.

  • Competing interests: All authors have read and understood BMJ policy on declaration of interests and declare funding from the National Institutes of Health, NHLBI (R01 HL130735). The funders had no role in the design or conduct of the study; collection, management, analysis, or interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication. DM reports personal fees from Acasti Pharma, GOED, DSM, Nutrition Impact, Pollock Communications, Bunge, Indigo Agriculture, and Amarin; scientific advisory board, Omada Health, Elysium Health, and DayTwo; and chapter royalties from UpToDate (not related to this work). JAR reports personal fees from Tres Montes Lucchetti, not related to this work.

  • Provenance and peer review: Commissioned; externally peer reviewed.

  • This article is one of a series commissioned by The BMJ. Open access fees for the series were funded by Swiss Re, which had no input into the commissioning or peer review of the articles. The BMJ thanks the series advisers, Nita Forouhi and Dariush Mozaffarian, for valuable advice and guiding selection of topics in the series.

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