Metabolic syndrome is a concept that was created by the American Heart Association to talk about behaviors that lead to heart disease. If you have metabolic syndrome it is a bad thing, but only because it means that you are by definition more likely to get heart disease —not that you already have it.
And to begin with, the role of diet in metabolic syndrome is quite complex and so a statistical correlation between diet and likelihood of heart issues is all that these doctors can claim.
However, having said that, the study referenced below is quite rigorous.
9514 people were enrolled and 3782 incidents of metabolic syndrome were investigated. What their research eventually showed, after 9 years of statistical inquiry, is that apart from all the obvious trouble-behaviors such as smoking and being fat there were certain other specific behaviors that have a statistically significant connection to heart disease. Specifically, the doctors mention the consumption of red meat, fried foods and diet soda. Each are correlated with increased incidents of metabolic syndrome. Dairy consumption was very slightly helpful in fending it off.
In other words, it is just (or perhaps even more) dangerous to your health to be drinking Diet Coke than eating a steak. Now, because these unhealthy food choices often go hand in hand, it seems quite possible that the red meat in question is being prepared in a less-than wholesome manner, such as the aforementioned deep frying.
What’s really concerning is diet soda. Because apparently it significantly contributes to your likelihood of having a heart attack. And yet, you don’t hear much in the media about this.
Here is the article in question, in case you think I am just making this stuff up:
oh, and if that wasn’t enough for you, here is a different study that says much the same thing: