Low-fat versus low-carb diet? One hundred forty-eight men and women without heart disease or diabetes enrolled in a study. Half of the subjects were randomly assigned to a low-carb diet 1640 g>d2, and the others were given a low-fat diet (630% of daily energy intake from total fat).

Subjects on the low-carb diet lost more weight after one year compared with those on the low-fat diet (an average of 8 pounds more). (L. A. Bazzano et al., Ann Intern Med 2014; 161(5): 309–318. doi: 10.7326/M14-0180)

a. Identify the response variable and the explanatory variable.

b. Was this study an observational study or an experimental study? Explain.

c. Based on this study, is it appropriate to recommend that everyone who wishes to lose weight should prefer a low-carb diet over a low-fat diet? Explain your answer.