At the FNCE last November in Boston, there was a debate titled “The Great Fat Debate – Is There Validity in the Age Old Dietary Guidance?”
The scientist participants were Walter Willett (Harvard), Dariush Mozaffarian (Harvard), Alice Lichtenstein (Tufts), and Lewis Kuller (Pittsburgh).
If you weren’t in attendance (like myself), thankfully the ADA put a video of the debate online here (~1h:15m).
This month’s issue of the JADA featured edited transcripts of each of the participants as well as a referenced summary of the debate from Kathleen Zelman (I uploaded it here; email me if you want copies of the transcripts). See especially the “Research Fueling the Debate” section for recent studies in this area, many of which I had mentioned in this post.
The overall conclusions that I gathered from the debate and considering some of their recent papers are essentially the following:
- Willett: Total fat doesn’t matter in regards to cardiovascular disease (CVD), diabetes, cancer, or adiposity, but he won’t go so far as to let saturated fat off the hook completely. Increase PUFAs (all types, as n-6 aren’t pro-inflammatory- they down-regulate NF-kB and are an insulin sensitizer) to reduce CVD risk. Higher fat diets may have a slight advantage for weight loss. A low-fat, high refined carbohydrate diet increases CVD risk. HDL goes up and triglycerides down when fat is substituted for carbohydrates. Nurses’ Health Study data suggests no relationship between total fat and CVD. Early RCTs found non-significant reduction in coronary heart disease (CHD) risk from low-fat diets, but replacing saturated fat with PUFA reduced risk. The “focus on reduction of fat in dietary guidelines has been a massive distraction“. Advice for % of energy from fat should be removed from the dietary guidelines and total fat from food labels.
- Mozaffarian: Total fat doesn’t matter, nor does saturated fat seem to. The traditional Diet-Heart paradigm is based on ecologic studies, biomarker studies, and animal experiments. These are best for hypothesis generation, not solid conclusions. In cohorts and trials, total fat not related to CVD. Evidence accumulated disproving total fat/CVD link, now we are basically at the same place for saturated fat. Dietary quality is very important (like quantity). Many drugs targeting single biomarkers (LDL, HDL, glucose etc) have failed in efficacy. Messages to reduce either confuse the public, we should focus on carbohydrate quality and increasing PUFAs, and a food based recommendation system. The “average carb in the U.S. is worse than saturated fat” on the risk of CVD. Processed meats may increase risk of CVD while unprocessed does not. Milk & dairy may have slight benefit for CVD and stroke risk. Reducing fat often leads to an unintended increase in refined carbohydrates. Focus on saturated fat “confusing and impractical.” Nice photo of real foods at the end, to get the focus off nutrients.
- Lichetenstein: Total fat doesn’t matter. She presented a nice historical presentation on dietary guidelines and how they’ve changed over the years. Increasing PUFA/MUFA in place of saturated fat can lower CVD risk, but replacing saturated fat with carbohydrates isn’t really supported. Overall dietary pattern matters most. We need to worry about what is the replacement if fat is reduced in the diet. The press in general isn’t translating the correct messages about fat. We have to worry about simplifying messages too much.
- Kuller: Shouldn’t fixate on total fat, but saturated fats increase cholesterol and CVD, and we should get LDL below 100mg. Increase PUFAs. Kuller is adamantly anti-saturated fat and LDL obsessed, even though Mozaffarian (and the general consensus by many researchers in this area as well as a recent IOM review) emphasizes that we can’t limit our focus on LDL and should be using multiple biomarkers. Bold claim in “there is no scientific evidence for a change in dietary recommendations to reduce cardiovascular disease.” Eating behavior is biggest problem in American diet. 48% of our food is consumed outside of the home. A reduction in blood cholesterol has saved hundreds of thousands of lives.
So the unanimous conclusions here are that total fat doesn’t matter, and that PUFAs should be increased.
Zelman, K. (2011). The Great Fat Debate: A Closer Look at the Controversy—Questioning the Validity of Age-Old Dietary Guidance Journal of the American Dietetic Association, 111 (5), 655-658 DOI: 10.1016/j.jada.2011.03.026