Don't worry Geoff. I'm very much in the same boat as you, in fact I took a week off the plan just to reassure myself that I could still put weight on, and I put on 0.5lb. Like you, I had never really heard of 5lb+ losses in one week, but that's the wonder of the plan - you eat healthier food and a balanced diet without really realising it, and your body is loving it!
One thing I would say though is to eat your syns. With your starting weight (similar to mine) you will easily lose weight if you go the full 15 each day, and you won't get cravings or feelings of abstension that you are going to encounter if you don't already. On SW, NOTHING is banned! Eat whatever you like within the plan!
Do remember that at your/our weight (and I'm guessing you aren't that much older than me, and live a lifestyle with light activity) you need anywhere between 2900-3200 calories a day just to live. I was eating about 4000-5000 every day, so if you are cutting right down to 1500,
which the plan will make you do without realising it or having to count a single calorie, you are cutting 2500 calories EVERY DAY out of your diet. Yet you are still eating enough to survive on, your body is still getting all the nutrients it needs, but is burning fat from its reserves. That 2500 calories less equates to a 5lb per week weight loss (500 less each day for a week is a 1lb loss). Hope this makes sense!
If you are still genuinely worried, talk to your Consultant or go and visit your GP but take your food diary along with you. Hopefully they will laugh cheerfully and say "told you so"
