Vitamin B12 is water-soluble which means it gets excreted out of the body when it is taken in excess. Therefore, if you’re already getting enough vitamin B12 in your diet and don’t have a nutrient deficiency, it’s unclear whether increasing your intake of vitamin B12 help with weight loss. However, some research shows that B-12 can increase energy and endurance during exercise which can consequently help with weight loss but there is not enough evidence to make this claim.