Ill be direct (for a change).
Yoga can lead to weight loss. Yoga can also lead to weight gain. Yoga can lead to truly being more mindful. Yoga can also lead to being an arrogant pain in the ass. Yoga can lead to the deepest embodiment of non-violence. Yoga can also lead to militant internal violence in the name of non-violence.
Okay, so I will not be direct:-)
No external diet, none, will have a lasting effect unless it comes with a precursory internal shift. The change must first come from inside.
Then once that happens the student must understand that not everyone’s ideal body weight is the cover of Shape magazine. Bodies operate differently and while I’m not advocating obesity I am illustrating that expectations should be reasonable rather than societal.
After the internal shift, then an educational process of the two components of eating would be required: what not to eat and what to eat. That, in conjunction with the proper apportionment of fat, protein, and carbs AND an increase in activity levels will often manage weight.
However Yoga is not a weight loss system nor should it be. Just like Yoga is not a muscle fitness system, nor should it be. Just like yoga is not a flexibility system, nor should it be. Yoga does however contain some elements of each of these - in additional to about 10,000 other things.