An article in the Journal of the Academy of Nutrition and Dietetics reported on a study of diet in subjects with moderate to severe acne. Read the excerpts from the abstract and answer the questions that follow. (Burris et al., “Differences in dietary glycemic load and hormones in New York City adults with no or moderate/severe acne,” Journal of the Academy of Nutrition and Dietetics, vol. 117 [September 2017]: 1375–1383) Methods: Sixty-four participants (no acne, n = 32; moderate/severe acne, n = 32) were included in this study. Participants completed a 5-day food record, had blood drawn and completed a questionnaire to evaluate food-aggravated acne beliefs and acne-specific quality of life. Results: Participants with moderate/severe acne consumed greater total carbohydrate compared to participants without acne. Participants with moderate/severe acne had greater insulin compared to participants Without acne. Although there were no differences between groups, 61% of participants reported food-influenced acne.

a. Was this a controlled experiment or an observational study? Explain how you know.

b. Assuming the study was properly conducted, can we conclude that higher consumption of carbohydrates causes more severe acne? Explain.