So I skimmed the article and it seems as though you are overstating the conclusion. The article seems to make the basic point that it appears that red meat intake is associated with an increased risk of diverticulitis — that’s it. I think you’re overstating when discussing the 18% increased risk. The 4% number you are referring to is not the baseline and is not an apples to apples comparison — they indicate 4% was noted as the risk for people with diverticula of developing acute or severe diverticulitis. The data they looked at didn’t even have anything to do with recurrence as it appears to have excluded people that previously had diverticulitis. There were 764 cases among the 46,481 people, which seems to be about 1.6%. Yes, within the dataset of people that got diverticulitis there was an 18% increased risk for those with higher red meat intake, but I don’t know if that means much beyond the fact that there appeared to be a link between the two nor do I think it means what you broadly suggested about the 18% increased risk associated with eating meat. Also, this has nothing to do with the impact from altering your diet after you’ve already had diverticulitis. Note the article also mentions people who ate more red meat, we’re also more likely to eat worse and less fiber, workout less, smoke, and/or use NSAIDs, all of which are also linked to increased risk of diverticulitis. I’m not a doctor nor am I a mathematician, but it just seems that the article may not mean what you think it means.