The Study
Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU study
This study shows a link between eating more saturated fat and lower insulin sensitivity in healthy people, but we can't be sure it's the fat causing the change because we don't know all the details about how the study was done. It's like noticing ice cream sales go up when it's hot — they're linked, but one doesn't necessarily cause the other.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study looked at what happens when people eat more healthy fats (like olive oil) instead of unhealthy fats (like butter) for 3 months.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 558 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes, this matters.
- 2Even in healthy people, eating the wrong kinds of fat can make your body handle sugar worse and raise heart disease risk over time.
- 3People eating bad fats became 10% worse at using insulin.
- 4Good fats didn't change insulin use.
- 5LDL cholesterol went up 4.1% with bad fats and down 5.2% with good fats.
- 6Eating too much fat overall canceled out the benefits of good fats.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Diabetologia
Year
2001
Authors
B. Vessby, M. Uusitupa, K. Hermansen, G. Riccardi, A. Rivellese, L. Tapsell, C. Nälsén, L. Berglund, A. Louheranta, B. M. Rasmussen, G. Calvert, A. Maffetone, E. Pedersen, I. Gustafsson, L. Storlien
Related Content
Claims (4)
If you're eating a lot of fat—more than 37% of your daily calories—switching to healthier fats like olive oil might not help your body respond to insulin better. But if your overall fat intake is lower, making that switch could actually help.
Eating a lot of saturated fat might make your body less responsive to insulin and cause fat to build up in your liver. If you also eat a lot of protein, it could push your body to make more sugar, which might raise your blood sugar—especially if you're prone to it.
Swapping out bad fats (like butter and fatty meats) for good fats (like olive oil and avocados) can help your body use insulin better—even if you're not changing how many calories you eat.
Eating certain fats can change your 'bad' cholesterol — saturated fats go up a little, but monounsaturated fats go down, even if you're already healthy.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.