This article is going to show how u can do weight watchers for free, but first off, lets see why weight watchers is so successful. The 4 pillars of success; Food, exercise, behavior & support.
1 Hip muscles. Lunges work all of the gluteal muscles in the hips, primarily the gluteus maximus that is used to extend your hips. Taking large steps during a lunge can further engage this muscle. The gluteus minimus and gluteus medius are also used to stabilize your body throughout the lunge.  Thigh muscles.
The gastrocnemeus and soleus muscles of the calf are both worked differently during lunges. The soleus is worked in the rear leg to plantar flex, or lift your heel off the ground. The gastrocnemeus is used to dynamically stabilize the knees throughout the exercise.