The study included 44 overweight women (BMI of at least 25) diagnosed with invasive breast cancer after the age of 50 who were within four years after completing treatment. The order of the diets was randomly assigned, and participants followed each diet for eight weeks. Women were provided with meal plans and recipes for each diet and were asked to keep three-day food diaries at weeks four and eight of each diet and during months three and six of the follow-up period. Weight was measured and blood samples were taken at the end of each study period.

Overall, 28 of the 44 women completed both diets and 19 of the 22 eligible for the six months of follow-up chose to follow the plant-based olive oil diet. All 19 women either maintained their weight loss or lost additional weight during this time.

"I found this surprising, particularly since the low-fat diet is more commercial and more recognizable to women, so I thought the preference would be more evenly split," says Flynn, who is also an assistant professor of medicine at The Warren Alpert Medical School of Brown University. "But the women who enjoyed the olive oil diet said not only were they losing weight but they weren't as hungry. That's because they were advised to include fat in the form of olive oil or nuts at each meal, so they weren't as likely to snack between meals, which can cause weight gain."

As researchers expected, the plant-based olive oil diet also resulted in lower triglycerides (a type of fat found in the blood) and higher high-density lipoprotein cholesterol (HDL, or "good" cholesterol). High triglycerides and low levels of HDL have both been linked with increased cancer risk.

Source: Lifespan