A research study aims to assess the impact of a dietary intervention on weight loss. The study involves 120 participants who are randomly assigned to two groups: one group follows a low-carb diet, and the other group follows a low-fat diet. The participants' weights are recorded at the beginning of the study and after 6 months. What is the independent variable in this study? The participants' weights after 6 months The type of diet followed (low-carb or low-fat) The number of participants in each group The duration of the study (6 months)