Methods: oncology nurses and physicians at an infusion center were offered participation in the study. After signing the study consent form, participants completed a baseline questionnaire that assessed their typical work schedule and current snacking behavior on work days. They also completed the RS-14, which is a standardized questionnaire assessing resiliency.[score interpretation: > 90 points = high; 65-84 = moderately low to moderate; < 64 = low]. They had 2 fasting blood samples separated by 2 to 4 days before starting the 4 weeks of meals. The second blood sample was on the day the meals started. Height and weight were measured at the time of the second blood sample. The meals were recipes provided by one of the investigators to nutrition services that were based on a plant-based, olive oil diet developed by the investigator. The meals contained a variety of vegetables, 1.5 to 2 tablespoons of extra virgin olive oil (Corto Olive Co.) and 2 to 3 ounces (dry weight) of starch per serving. The energy content of the meals ranged from 450 to 600 kcals with most averaging 550 kcals. The meals were brought to the unit for the participants. The participants completed forms on the day they ate one of the meals that assessed the participant’s experience. They were asked if they ate the whole meal, how long it took to eat it, when they perceived hunger after eating the meal and if they snacked before 5 p.m., which was considered the time at which they should expect to be hungry. A snack was an occasion of eating anything with calories. Two fasting blood samples were completed at the end of the 4 weeks, again separated by 2 to 4 days. Weight was measured at the second blood sample as was the completion of the RS-14 questionnaire. The two blood samples at baseline and post 4 weeks of the intervention were averaged to receive a mean value for each participant. The baseline (base) values were compared to the post- four weeks (FU) of the olive oil meals using Paired t-tests.
Results: nineteen staff signed study consent forms and 15 completed the study. The results (mean +/- SD) are for those completing: age 47.0+/-13.7 yrs; n=13 oncology nurses, 1 physician, 1 physician assistant. Glucose (mg/dl) base 99.6+/-10.3 v FU 95.2 +/-11.8; p=0.008; Insulin mU/L base 7.4 +/-2.5 v FU 6.4 +/-2.3; p=0.12; HOMA (Homeostatis Model Assessment of Insulin Resistance; healthy 0.5 to 1.4; >1.9 indicates early IR] base 1.8+/-0.6 v FU 1.5 +/-0.7; p=0.09; body weight (kg) base 66.2 +/-6.9 v FU 66.1 +/-6.8; p=0.77; BMI (kg/m2) base 24.2+/-3.1 v FU 24.2 +/-3.1; p=0.75; RS-14 base 79.8+/-9.0 v FU 82.3 +/-7.0; p=0.11. Average days/week afternoon snacking base 2.8 +/-0.8 v FU 1.5 +/-0.7; p=0.001.The decrease in fasting blood glucose was unexpected as the baseline mean was at the cutoff for normal and there was no change in body weight. Nine of the 15 had decreases in fasting insulin. There were 7 participants at baseline with a HOMA-IR >1.9, the cutoff for insulin resistance, and 5 of these reduced their HOMA-IR value to < 1.9 post-olive oil meals. Nine of the 15 improved their HOMA-IR score. The group overall was of normal weight. Six participants had a BMI > 25.0 kg/m2 at baseline and 3 of these decreased their BMI after 4 weeks of the olive oil meals. The baseline mean RS-14 score indicated moderately high resiliency. Seven of the 15 improved their RS-14 score post-olive oil meals. Twelve of the 15 decreased their snacking while on the olive oil diet.
Conclusions: Consuming a lunch that is plant-based and includes extra virgin olive oil for 3 lunches per week may improve overall health by decreasing fasting blood glucose and snacking. The results of this pilot study will be used to design a larger study that will continue to assess glycemic control, likely in hospital nurses with impaired glucose tolerance and/ or type 2 diabetes. A longer study could also lead to improvement in body weight for those with unhealthy weight at baseline, based on earlier studies with the plant-based, olive oil diet.