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Can a Low-Fat Diet Reduce the Risk of Dying From Breast Cancer? -- Heard in the Halls: Voices From the 2019 American Society of Clinical Oncology Annual Meeting
Rowan Chlebowski, M.D., Ph.D.
June 2, 2019

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Dr. Rowan Chlebowski, of the Los Angeles Biomedical Research Institute, explains the results of the latest analysis of data from the Women's Health Initiative.

Running time: 2:50

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Rowan Chlebowski: Hi, I’m Rowan Chlebowski from Los Angeles Biomedical Research Institute at Harvard UCLA Research Medical Center, and we’re reporting a study from the Women’s Health Initiative. We’re studying, in 1993 we randomized 48,835 postmenopausal women between the ages of 50 and 79. These are women who had no prior breast cancer and normal mammograms on entry, randomized them to a dietary intervention targeting modest dietary fat intake as it turned out, and increased fruit, vegetables, and grains, so very similar to DASH cardiovascular disease diet, but a little more emphasis on total fat versus the usual diet comparison group. The intervention was 8 ½ years. Now, after 19.6 years median follow-up, we now have a statistically significant reduction in deaths from breast cancer, which was 23%, which was the first intervention of any kind, including the chemo preventions, that have been able to establish this endpoint. Now the women did lose — it wasn’t an intervention target — they did lose 3% of their body weight. That difference in weight was maintained. But when we adjusted for it, it didn’t change the outcome. A major effect was a reduction in ER-positive/ER-negative kind of breast cancers.

There can always be a question of, did people change what they eat? But when we have 19,540 women lost 3% of body weight and 29,294 didn’t lose body weight, then we’d have to have this tremendous conspiracy that all those women would get together. So it’s a question of what did it but it’s really dietary moderation. You could do it probably with substitution for low-fat or no-fat dairy, cut down meat portion sizes, and eat fruits, vegetables, and grains, and most people could do that. And of which 19,000 people who did, so we’re very pleased with the result. We think that should move into some of those guidelines like that.

Jamie DePolo: And how did you get the women to reduce the fat in their diets? Did you counsel them, were there phone calls, how did that work?

Rowan Chlebowski: Yeah, so this was pretty intensive. There was 18 every-3-week visits the first year, so in a group of 12 to 16 women. And we had a previously developed and validated intervention plan so there was individual components all designed each time, and it had behavioral motivation with the hope that it would continue afterwards. So then it was quarterly visits until the end of the dietary intervention, but no contact with nutritionists after 8.5 years. And it’s remarkable that that difference is being maintained.

Jamie DePolo: And what about exercise? Was that part of this at all?

Rowan Chlebowski: No, exercise wasn’t a component. We’re looking at the exercise now. There wasn’t a major difference at the start but there’s always a question if you’re doing a lifestyle intervention whether physical activity will come along for the ride.

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