This will vary for each individual and depends on certain factors such as how healthy your gut flora and digestive system are, how much fiber you normally consume, and what other foods are you consuming during the day. Added fiber from fruits and veggies and boosts are great to help keep things flowing so you should see "side-effects" most likely within a day or so. Check out this article on how to keep things moving with fiber! https://www.nutriliving.com/blog/getting-things-moving-fiber