As said above, totally posdible to eat too much free food. But don't worry too much about calorie deficits as it will (in my experience) eventually lead to calorie counting - and that defeats the whole point of SW! Logicslly, calorie defict maths means someone who lost 5lbs in a week (which have done once) would have had to create a Calorie deficit of 17,500 calories, or 2,500 a day - which would be impossible for most if not all of us - & especially me!
If you do the plan properly (ie stop when you are full rather than clearing your plate then you will lose weight.
Try these tips for portion control
1) ditch all your massive plates - my old housemate used to work at toby carvery & all our plate were their massive ones - its amazing how much food tou can fit on one, and then you eat it all!
2) if there are 2 if you eating, dish out your dinner into 3 portions.
3) if you're still hungry when you've finished, have a glass of water, wait 10 mins. If still hungry, have some of the 3rd portion. Most of the time you won't - in which case you have a meal for lunch the next day.