The science agrees.

Impacto de diferentes etiquetados frontales de alimentos según su calidad nutricional: estudio comparativo en México

Given the controversy and the political overtones of these public service endeavors, one would think that there would be plenty of research to prove or disprove their usefulness. Sadly, there is not. Here is a study in English that saw a benefit:

https://www.foodbusinessnews.net/articles/12827-benefits-seen-in-calorie-count-posting-on-menus

Much of the other publicly available articles are subjective.

This is the dilemma of the public health official who sees the number of heart attacks, strokes, diabetes, etc. and the concurrent costs of life and national treasure. What can one do? It is reminiscent of F.D.R.'s approach to the Great Depression: “One thing is sure. We have to do something. We have to do the best we know how at the moment... If it doesn't turn out right, we can modify it as we go along.”

His fifth cousin, Theodore Roosevelt said, “In any moment of decision, the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.”

For more information than you can imagine could be available about diet and health, consult NutritionFacts.org and ForksOverKnives.com. Or better yet, visit Mitos / Entre Zankas and see if you can get the husband and wife chef team to engage in a "discussion" of the health merits of each's culinary offerings.

In your experience, Rob, do many people change their buying habits due to these warnings? Maybe gradually...?

My family finds the warnings helpful. We believe they tend to raise consciousness and steer us towards better nutritional habits. The science agrees.

Impacto de diferentes etiquetados frontales de alimentos según su calidad nutricional: estudio comparativo en México

In your experience, Rob, do many people change their buying habits due to these warnings? Maybe gradually...?

@JeffMN

Though you directed your inquiry to Z Rob, I'll chime in to respond:

Although those labels aren't necessarily "fine print ", IF I had to hazard a guess, they are more often ignored than obeyed, and the warning goes in one eye and out the other The fine print gets ignored.

Nevertheless, the label may call the attention of the consumer, & possibly, it may heighten their awareness about those types of foods

Mexico is not longer foreign to us because we now live here, and welcome this new labeling. It is already over a year old.

Stunning, the appearance, in the two years since we've been here, of these ominous black stop-sign icons on nearly every packaged food item we saw at the Mega yesterday. "Exceso grasa, exceso azucar, exceso sodio."
Right now I'm so frightened that I've decided I'm on a strict tequila diet!

Ha! My wife and I like them and think they're a good idea. Helps to keep folks healthier.