I really do not think anyone is adding lead to food to increase the weight when you could use any metal compound with a roughly similar density like iron oxide (which even has an E-number) and thereby not obviously poison anyone for the sake a few grams and get yourself discovered immediately.
And if you wanted to weigh down the container, lead costs more then iron per kg: just make the existing iron-based can thicker.
And if you wanted to weigh down the container, lead costs more then iron per kg: just make the existing iron-based can thicker.