When you are citing a statistic or another specific fact, a signal phrase is often not necessary. In most cases, readers will understand that the citation refers to the statistic or fact (not the whole paragraph).

Legislation, however, is not a popular solution when it comes to most Americans and the food they eat. Nearly 75% of Americans are opposed to laws that restrict or put limitations on access to unhealthy foods (Neergaard and Agiesta).

There is nothing wrong, however, with using a signal phrase to introduce a statistic or other fact.

Legislation, however, is not a popular solution when it comes to most Americans and the food they eat. According to a nationwide poll, nearly 75% of Americans are opposed to laws that restrict or put limitations on access to unhealthy foods (Neergaard and Agiesta).