Duke University researchers found that diets low in carbohydrates are effective in controlling blood sugar levels (Westman et al. (2008)). Eighty-four volunteers with obesity and type 2 diabetes were randomly assigned to either a diet of less than 20 g of carbohydrates/day or a low-glycemic, reduced calorie diet (500 calories/day). Ninety-five percent of those on the low-carbohydrate diet were able to reduce or eliminate their diabetes medications compared to 62% on the low-glycemic diet.
(a) Was this study an observational study or an experiment?
(b) Can researchers conclude that a low-carbohydrate diet causes an improvement in type 2 diabetes? (c) Can researchers extend their results to a more general population? Explain