Your are correct..U need to eat at least 2500 cals a day. If U are only eating lettuce for carbs I would suggest adding a bit more. Maybe a cup of green beans, or califlower. There are a lot of low-carb veggie choices U can choose from. I workout a lot but not into a lot of weight lifting yet. I have heard it suggested to not do any weight training the 1st few weeks of low-carbing to allow your body to adjust. Im sure someone else will post to help U with that.