I just finished my first Whole 30 this past Friday. I'd say it was pretty successful, though I want to tweak it next time I do it. Successful in that I truly did not cheat, and didn't have a hard time fighting my own fierce sugar addiction. I seemed to resign myself really easily to going through the thirty days without these foods, and it wasn't a big deal. For Sterling, who thinks it would be impossible to go without legumes...it's only thirty days! It is possible.
The reason they say give X up for that amount of time, is in the focus on the re-introduction that starts immediately after the thirty days. That's when different foods we couldn't eat are methodically re-entered back into the diet. Within the program, they want you to gain a sense of which foods are problematic, and I guess there are enough people out there with allergies to soy and beans that they wanted to eliminate these for a month to address that potential allergy.
I found it doable, but I have time to prep vegetables, shop, plan meals, etc. One of my cookbook authors went into detail about spending a lot of her Sundays on shopping and food prep. Maybe that's not your thing. I don't mind it right now.
I was happy to be able to say that I could easily go off sugar. As a disclaimer, I must say that I have bungled the re-introduction phase in that I almost immediately had a couple of sweets, two days in a row. I don't really care about the precision of this phase; I know that I basically should be avoiding sugar and particularly gluten, which gives me weird symptoms. I found out that I don't miss dairy much at all, and I could easily go without grains.
Socializing at other people's homes was a little bit of a hassle, but I got through it unscathed. Maybe long-term this would be more annoying if I wanted to be super-strict (which I am not sure is necessary).
I also find eating a lot more meat to be weird. I had mentioned tweaking my next Whole 30. What I want to do is to eat more fish and chicken and maybe beef once a week. Less sweet potatoes and definitely less fruit (which I used as a crutch due to the sugar cravings). I wasn't eating low-carb at all on this. I also want to be more mindful about eating only till I'm full, or not completely full. In other words, this time around I was all about the elimination of the "problem" foods, particularly sugar. I proved that I could do it. Next time I really want to build better eating habits.
I did lose a little weight though I am not sure how much--I didn't weigh myself. (I would have been much more appreciative to have taken Before pics, rather than have a before weight.) I'm guessing I lost 5-8 pounds; my clothes got slightly looser and for sure I see a difference in my face, though other people have more dramatic results.
I was fairly active during the month. Not the way I would be in summer, but I continued my 2x/week kettlebell classes, and a lot of dancing.
I think it's a good, solid program to shift your relation with food...or at least mine. Incidentally, my husband didn't go on it with me. He ate the foods I cooked, and didn't seem to mind getting the extra meat and not a lot of grains. But at parties he ate desserts, etc. I would be unhappy if I felt I had to continue a regimen (strictly) because of my spouse--if it didn't agree with me.