Background: Traditional diets that include moderate to high intakes of extra virgin olive oil have been related to a decrease in breast cancer risk. We hypothesized that an olive oil-enriched diet would lead to greater weight loss and acceptance, compared with a standard diet, in women previously diagnosed with invasive breast cancer.
Methods: Participants consumed a National Cancer Institute (NCI) diet (total fat > 15% and < 30%) and a plant-based olive oil diet (PBOO; > or = 3 tablespoons of olive oil/day) for 8 weeks, each with random assignment to the order. We established a weight loss goal of at least 5% of baseline weight. After completion of the two diet trials, each participant self-selected one of the diets for an additional 6 months of follow-up for weight management. Body measures were done before and after each diet and after follow-up; fasting blood samples were collected after each diet and after follow-up.
Results: Forty-four overweight women started and 28 completed the 44-week protocol. Twelve (80%) of the 15 women who started with the PBOO diet achieved a weight loss of > or = 5% compared to 4 (31%) of the 13 who started with the NCI diet (p < 0.01). Nineteen of the 22 women eligible for follow-up chose the PBOO diet, and all completed the study. Of the 3 women who chose the NCI diet for follow-up, 1 completed the study. The PBOO diet resulted in lower triglycerides (NCI 105 +/- 46 mg/dL, PBOO 96 +/- 37 mg/dL, p = 0.06) and higher high-density lipoprotein cholesterol (HDL-C) (NCI 64 +/- 13 mg/dL, PBOO 68 +/- 12 mg/dL, p = 0.001).
Conclusions: An olive oil-enriched diet brought about greater weight loss than a lower-fat diet in an 8-week comparison. Moreover, these women chose, overwhelmingly, the olive oil-enriched diet for 6 months of follow-up. An olive oil-enriched diet may be more efficacious for weight loss in breast cancer survivors than a standard lower-fat diet.