mr. Frost doctor dr. Kerr have instructed him to lose 30 lb and to improve his health dr. Curl one mr. Fries to try three different diets to find the one that works best for him he gives Mr fraud information and meal plan for a low carbohydrate diet a low fat diet and a vegetarian diet and tells him to follow each diet for two full weeks mr. Fries will record what you eat each day and his weight every morning before his first meal dr. Turner instruct him not to eat after 7 p.m. on any of the diet and to not start an exercise program until after his next check up appointment his doctor will come compare the results of the three diet following the investigation

if mr. Fries followed all of dr. Kurt instructions which will be a controlled variable in his investigation