On another thread I published my findings: What's the inulin content of different Plenny shake flavors? - #10 by gerimy
The trick is to gradually increase or decrease inulin intake (increase or decrease by about 2g/day week-to-week and keep the intake regular), and avoid intake of other foods in the hours around taking an inulin-containing shake. In other words, use the shake as a full meal replacement for at least one meal a day. I find it also works as a pre-breakfast for a low-FODMAP breakfast.
To top up calories right after a meal, especially a high-FODMAP meal, you’ll need a non-inulin shake.