Isn't the proportion of people who are obese and therefore go on this diet also going to be much higher? They appear to not have controlled for anything.

So in essence the implied cause and effect here for most people reading this headline (intermittent fasting causes cardiovascular death) is actually backwards: (people who are unhealthy are more likely to initiate an IF diet).

Reminds me of the story around diet soda. Some initial association studies found that there was an association between diet soda and several negative health outcomes but upon further investigation the evidence seems to be that it does not cause them.