To update the Dietary Guidelines, as required by law, the Secretaries of the DHHS and the USDA formed an external Dietary Guidelines Advisory Committee made up of prestigious researchers and scientists in the fields of nutrition, health, and medicine. The 2015 advisory committee was charged with reviewing the 2010 Dietary Guidelines to determine topics for which new scientific evidence is likely available and to review that evidence to inform the development of the 2015-2020 edition. The committee used 4 approaches to review the available evidence: original systematic reviews; existing systematic reviews, meta-analyses, and reports by federal agencies or leading scientific organizations; data analyses; and food pattern modeling analyses. The work of the committee was submitted to the DHHS and USDA in the scientific report of the 2015 Dietary Guidelines Advisory Committee and made available for public comment. In addition to the committee report, the DHHS and USDA obtained input from federal nutrition and medical experts and comments from the public to develop the 2015-2020 Dietary Guidelines.