While I understand the comparison you're trying to make, I'm not sure weight is the best estimation here. A whale can be heavier without being larger. While the whale may weigh 1000x more, it appears to be only around 10x as big (sperm whales are 40 feet long, and somewhat wider than humans).

If you take a look at the picture in the article, and analyze what it had ingested: "115 drinking cups, four plastic bottles, 25 plastic bags and two flip-flops," it seems much less trivial than a teenager ingesting a teaspoon.

A better comparison would be that, size-wise, it is the same as a teenager ingesting 2.5 plastic bags, 15 drinking cups; that alone seems like enough to cause serious health issues.