Hi Fairycake!
I have never done WW online or fitness pal, so hopefully someone will chime in on those, but I am currently doing low carb and it's working extremely well for me. I am doing a modified Slow Carb Diet. (You can google Slow Carb Diet to get the "real" diet, which came from the book
4-Hour Body by Tim Ferriss.) Here is what I do: For 6 days, I eat meats, legumes, non-potato veggies, veggie-like fruits (like tomatoes, cucumbers, squash), nuts in moderation, peanut butter, cottage cheese, eggs, and black olives. I eat any condiment or salad dressing I want. I drink 6-8 oz of water a day, Diet Dr. Pepper and green tea. For these 6 days, I avoid breads and grains (including corn), pasta, dairy (other than eggs and cottage cheese), fruits (except veggie-like fruits), potatoes, and sweets. I count no calories. I count no carbs. I don't eat every 4 hours (like the book says). I don't pay attention to numbers at all. I eat when I'm hungry. I stop when I'm full. I try not to eat late at night. The 7th day of the week (I've chosen Saturday) is an allowed and even recommended Cheat Day. I eat whatever I want as much as I want, but again, I eat when I'm hungry and stop when I'm full. I never feel "starved" because my blood sugar no longer spikes on a high-carb diet, and I'm never tempted to break my diet or binge on forbidden foods because I can have them on Cheat Day. I'm not much of an exerciser, but I try to walk for 20 minutes each day. The thing is I have a carb sensitivity so this diet works for me. I don't know if it would work for you, but if you are going to go low-carb, you might want to try it. Whichever plan you choose, good luck!