Scientists finally define what it means to be flexitarian

A new review finally puts numbers to the “flexitarian” diet, and shows that the world’s nutrition advice is shifting toward more flexible, plant-rich eating, even if the name stays unofficial.

Review: Vegetarianísh—How “Flexitarian” Eating Patterns Are Defined and Their Role in Global Food-Based Dietary Guidance. Image Credit: VectorMine / Shutterstock

In a recent systematic review published in the journal Nutrients, researchers collated and synthesized literature to define the “flexitarian” dietary pattern. As interest in plant-forward diets grows, diets that reduce human dependency on animal products are becoming increasingly popular, but remain poorly defined.

Review findings revealed a consensus summary definition of a flexitarian diet as consuming dairy, eggs, meat, or fish at least once per month but less than once per week. Official food-based dietary guidance from 42 countries further revealed that while no country explicitly recommends a “flexitarian” diet, the guidelines of many implicitly support such a pattern, particularly by advising their citizens to limit their intake of red meats, though most encourage regular dairy and fish consumption based on analysis of the guidelines.

As society increasingly recognizes the physiological and environmental benefits of plant-based diets, vegetarian diets continue to gain traction. While a substantial portion of individuals (particularly in the West) are opting for strict vegetarian and vegan diets, an even larger number of people are embracing a more moderate approach: the “flexitarian” diet.

Broadly understood as being “flexibly vegetarian,” this poorly defined eating pattern postulates a reduction in the consumption of dairy, eggs, meat, or fish (without eliminating them entirely), making it a more accessible choice for many. Unfortunately, the lack of a clear, scientifically defined definition confounds the assessment of these dietary patterns’ efficacy and physiological safety, effectively preventing public health recommendations.

A clearer definition of a flexitarian diet would allow for the comparisons of this diet against other popular eating patterns (such as the Mediterranean diet and DASH) and official dietary recommendations.

The present review aimed to address these knowledge gaps by conducting a two-part study. Firstly, a systematic literature review was undertaken to create a draft quantitative definition of a “flexitarian” or “semi-vegetarian” diet. This was accomplished via a custom keyword search conducted through two online scientific databases: PubMed and Scopus.

Title, abstract, and full-text screening identified a total of 86 peer-reviewed articles that used terms like “flexitarian” or the nearly equally common “semi-vegetarian,” making them eligible for review inclusion. From each relevant paper, specific definitions and quantitative parameters used to describe reduced-animal-product dietary patterns were extracted.

Secondly, the review analyzed the Food-Based Dietary Guidance (FBDG) recommendations obtained from the United Nations Food and Agriculture Organization, representing 42 English-translated nations. Study data comprised quantitative recommendations for the consumption of animal-based foods (dairy, meat, eggs, and fish) for a dietary pattern of approximately 2000 kcal per day, excluding guidelines lacking quantitative portions.

While individual definitions varied widely between studies, a synthesis of qualitative parameters was able to establish a summary definition: “consuming dairy, eggs, meat, or fish at least once a month but less than once a week.”

Applying this definition to FBDG recommendations across 42 nations revealed:

• No guidelines use “flexitarian” terminology
• Sri Lanka explicitly describes a similar “semi-vegetarian” pattern
• 14 guidelines implicitly support meat reduction principles (e.g., Germany’s plant-based ratio, Spain’s 3x/week meat limit)

Critically, conflicts emerged for dairy and fish:

• About 67% (28/42) of guidelines recommend daily dairy intake
• About 43% (18/42) explicitly promote weekly fish consumption
• Flexitarian reduction of these foods directly opposes most guidelines

Feasibility assessment showed:

• Not possible under guidelines requiring daily animal products (Albania, Bangladesh, Ethiopia)
• Requires careful adjustments in countries with grouped animal-food categories (Jamaica, Belize, South Africa)
• Possible in 28 countries when reducing specific animal foods

The systematic review establishes a clear summary definition of “flexitarian” using frequency parameters, opening the doors to future standardization. While official guidelines avoid the term “flexitarian,” many align with its core principle of reducing red meat.

The stronger policy recognition of “semi-vegetarian” (Sri Lanka) versus “flexitarian” (none) highlights terminology gaps. Despite cultural and definitional variability, this framework helps align public health guidance with sustainable eating trends.

Notable limitations: The study excluded non-English FBDGs and guidelines without quantitative recommendations.