To systematically summarise people's health-related values and preferences related to fat intake.

We searched five databases for studies reporting people's perspectives on fats. Screening, data extraction and risk of bias assessment were performed by two independent reviewers. Data was analysed using a convergent integrated approach and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation methodology.

Qualitative and quantitative studies from any country or language.

Primary studies of adults, with or without cardiometabolic conditions.

From 52 166 records, we included eleven quantitative and two 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 prioritising vegetable oil as a healthy fat. The evidence certainty for these themes was very low to moderate, rated down for risk of bias and indirectness issues.

People's perception of fats and oils in diets is complex and often contradictory; most viewed high-fat products as unhealthy and associated with weight gain, while vegetable oils were generally perceived as beneficial. However, views varied significantly depending on sex, 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 needed.

The aim of the study is (1) to assess the extent to which omnivores are willing to stop or reduce their consumption of red and processed meat in response to evidence-based information regarding the possible reduction of cancer mortality and incidence achieved by dietary modification; (2) to identify socio-demographic categories associated with higher willingness to change meat consumption and (3) to understand the motives facilitating and hindering such a change.

During an initial computer-assisted web interview, respondents were presented with scenarios containing the estimates of the absolute risk reduction in overall cancer incidence and mortality tailored to their declared level of red and processed meat consumption. Respondents were asked whether they would stop or reduce their average meat consumption based on the information provided. Their dietary choices were assessed at 6-month follow-up. Additionally, we conducted semi-structured interviews to better understand the rationale for dietary practices and the perception of health information.

The study was conducted among students and staff of three universities in Krakow, Poland.

Most of the 513 respondents were unwilling to change their consumption habits. We found gender to be a significant predictor of the willingness. Finally, we identified four themes reflecting key motives that determined meat consumption preferences: the importance of taste and texture, health consciousness, the habitual nature of cooking and persistence of omnivorous habits.

When faced with health information about the uncertain reduction in the risk of cancer mortality and incidence, the vast majority of study participants were unwilling to introduce changes in their consumption habits.