Watching Mexican TV channels like Televisa and TVAzteca, you'll notice that many TV commercials have captions at the bottom of the screen with what appear to read as cautionary messages. Snack commercials, for example, often have captions like "Come bien y haz ejercicio" (eat well and exercise) or "Llenate de energia" (fill yourself with energy). Makeup commercials often have messages like "Salud es belleza" (health is beauty). Beer commercials often come tagged with the phrase Todo con medida (everything in moderation). However, other commercials don't seem to have any captions at all.
Why do these messages appear in these commercials? Are they mandated by Mexican law? What is the motivation for these messages? Why do they appear on some commercials, but not all?