I have a bone to pick with the misconception of "toning." Unless someone is a complete beginner to the weight room, they won't gain noticeable muscle mass in a caloric deficit. In order to build muscle, you need to lift heavy and intake a surplus of calories every day.
Toning is the act of dieting fat off to reveal muscle. If your weight goes up while you are dieting, it is most likely always temporary water weight.
That said, I lift at least 3-4 times a week. From my experience in the gym, people who carry more muscle have a bigger problem with water fluctuations. There is a great article by Lyle McDonald that covers the science of water retention during dieting for those interested:
"Of Whooshes and Squishy Fat"