Please note that only a few flavors of spirutein have a hechsher.
this is not because all the others are non-kosher but because the manufacturer only had those flavors when they got the hechsher and havn’t expanded the kosher list.
some of the other flavors may not be kosher, you should stick to the few that have the hechsher
a protein drink such as this can be used to gain or lose weight,
depending on whether one uses it to replace a meal or in addition to regular meals.