FB - you need more fiber, not less. I'm not sure how much the low FODMAP diet would help, it is certainly not widely accepted for diverticulitis, but wouldn't hurt to try. Low fat does seem to help. Also, nuts, popcorn etc are safe to eat - this was an old myth that has been debunked. See below for more detailed information
Diet
Low fiber, high fat, and red meat — Low dietary fiber and high intake of fat or red meat are associated with an increased risk of symptomatic diverticular disease. Dietary fiber and a vegetarian diet may reduce the incidence of symptomatic diverticular disease by decreasing intestinal inflammation and altering the intestinal microbiota [
4,31,32]. In a cohort study that included over 47,000 men, after adjustment for age, energy-adjusted total fat intake, and physical activity, total dietary fiber intake was noted to be inversely associated with the risk of symptomatic diverticular disease (RR 0.58 highest quintile versus lowest quintile for fiber intake) [
31]. The risk of diverticular disease was significantly increased with diets that were low in fiber and were high in total fat or red meat as compared with diets that were low in both fiber and total fat or red meat (RR 2.35 and 3.32, respectively) [
31]. (See
'Definitions' above.)
However, the role of fiber in the development of diverticulosis is unclear. Several early studies suggested that low dietary fiber predisposes to the development of diverticular disease, but other studies have been conflicting [
3,31,33-41]. Fiber also does not reduce symptoms in patients with symptomatic uncomplicated diverticular disease [
39,40,42,43].
Seeds and nuts — Nut, corn, and popcorn consumption are not associated with an increase in risk of diverticulosis, diverticulitis or diverticular bleeding. In a large observational study that included 47,228 men between the ages of 40 and 75 years, there was an inverse association between the amount of nut and popcorn consumption and the risk of diverticulitis (HR nuts 0.8, 95% CI 0.63-1.01; HR popcorn 0.72, 95% CI 0.56-0.92) [
44]. In addition, no association was found between consumption of corn and diverticulitis or between nut, popcorn, or corn consumption and diverticular bleeding or uncomplicated diverticulosis. (See
"Acute colonic diverticulitis: Medical management", section on 'Recurrent diverticulitis'.)