(P14-087-23) How To Define Flexitarian Diets in Research?

Objectives: The overly broad definitions of “flexitarian” or “semi-vegetarian” pose a challenge to both observational and clinical studies on diets and health. The purpose of this review is to examine available definitions of flexitarian diets and to identify and characterize the key attributes of flexitarian diets and propose a working definition for further research.

Methods: A comprehensive literature search was conducted using PubMed to identify papers published during the last 10 years using definitions of “flexitarian”, “semi-vegetarian” or “meat-reducers”. Data extracted included type of protein foods consumed (i.e., red meat, poultry, fish, eggs, dairy and plant protein) and restrictions in frequency of animal protein consumption. A rating criterion was developed to identify the degree of restriction of animal source foods.

Results: The PubMed search identified 101 publications containing various definitions of “flexitarian” diets. Red meat (95%, n= 95/101) was the most restricted food group in frequency or amount, followed by fish (n=52%, 52/101) and poultry (46%, n= 46/101). Whereas red meat was specifically called out by name, fish was not. Plant-protein was mentioned in only 12 studies out of 101 (12%), indicating a focus on animal protein restriction rather than plant protein replacement. Only 44 studies out of 101 provided comprehensive information on the frequency of consumption (in days, weeks, months) of specific food sources of animal or plant protein.

Conclusions: There is a clear need for a standardized definition of flexitarian diets to facilitate across-study comparisons of diets composition and health outcomes. Thus far, the flexitarian diet has been conceptualized in terms of restricting meat, fish, and poultry as opposed to replacing them with a variety of plant-based proteins. Providing clear specifications of restricted animal protein foods and frequencies of consumption, while including the plant protein component in the definitions of flexitarian diets, would be a contribution to the literature.

Funding Sources: This work was supported by Nestlé Research, Lausanne, Switzerland.