Adults’ health-related values and preferences related to reducing or modifying dietary fat intake: a mixed methods systematic review
Joanna Zając, Małgorzata M Bała, Anna Prokop-Dorner, Pablo Alonso-Coello, Gordon Guyatt, Małgorzata Maraj, Krzysztof Więckowski, Karolina Zawadzka, Sylwia Warzecha, Zuzanna Sawiec, Dawid Storman, Claudia Valli, Mateusz Świerz, Ahmad Kamal Abadi, Jeremy P. Steen, Boris Castro, Montserrat Rabassa, Luciane Cruz Lopes, Ewa Płaczkiewicz-Jankowska, Bradley C. JohnstonAbstract
Objective:
To systematically summarise people’s health-related values and preferences related to fat intake.
Design:
The search through MEDLINE, EMBASE, Web of Science, SSCI, CAB, AGRIS, and FSTA up to May 2025 was performed. Qualitative and quantitative studies were included. Screening of abstracts and full-text articles, extraction and risk of bias assessment were performed by two independent reviewers. Data was summarised narratively, and the certainty of evidence was assessed using the GRADE methodology. Quantitative and qualitative evidence was analysed using a convergent integrated approach.
Setting:
This review aimed to include studies from all types of countries; however, most included studies were conducted in high-income settings.
Participants:
Primary studies of adults (aged ≥18 years), with or without cardiometabolic conditions were included.
Results:
From 52,166 screened records, we included 11 quantitative and 2 qualitative studies; studies were primarily conducted in high-income countries. Five main themes were identified: i) negative perception of fat in food, ii) positive perception of vegetable oil as being beneficial to health, iii) willingness to lower fat consumption, iv) willingness to pay for healthier fat content, and v) barriers towards unsaturated fat consumption. The most frequently reported themes were negative perception of fat and willingness to consume low-fat products, while prioritizing vegetable oil as a healthy fat. The certainty of the evidence for these themes was very low to moderate, rated down for risk of bias and indirectness issues.
Conclusions:
The perception of fats and oils in diets is complex and often contradictory, with most people viewing high-fat products as unhealthy and associating them with weight gain, while oils are generally perceived to be beneficial. However, these views can vary significantly depending on gender, age, and dietary patterns. Overall, the evidence supporting these perceptions is of moderate to very low certainty, and to inform guideline recommendations more research is need.