A few posts have appeared later than usual, and I apologize for the delay. There's a few things to keep in mind.
There's no immunity to alli in any way. It always blocks 25% of the calories in the meal at which it's taken.
Sometimes people don't lose weight for a few weeks and that's because the body just takes a "time out" to adjust to all the changes, and then weight loss resumes.
Other times weight loss halts because someone either has too many - or too few - calories and fat grams than is recommended. There are two great posts at the top of this message board about why calories and fat are so important -- and it's great information.
In addition, when someone has been on a plan for a while a few extra calories and/or slightly larger portions sneak in and weight loss slows. My recommendation is always to start weighing and measuring every food and beverage consumed throughout the day to be sure portion sizes are accurate. It's very, very easy to underestimate portion sizes and then weight loss slows.
So patience is needed for the plateaus, and accuracy is important to stay on track.
I hope this helps. Please let me know if you need anything else.
Pat Baird, MA, RD, registered dietitian