There Is, There Are, There Was, And There Were
When a clause begins with one of these expressions, the verb should agree with the first noun or pronoun after the verb, as long as that noun or pronoun is not part of a modifying phrase or clause.
There is no doubt that eating habits are changing in the USA.Notice that in the last example above, the first noun after the verb is people. But it's part of a modifying phrase, so the fact that it is plural is irrelevant. The next noun is ritual, and that's the one that matters. When you look after the verb and find the first noun outside a modifying phrase or clause, note whether it is singular or plural and then choose the verb to match:
A decade ago, there were no labels on packages boasting, "All natural; no preservatives."
Besides, there is now, among many young people, a ritual of daily diet and exercise.
Singular Plural there is there are there was there were