Big jumps are never a good idea in dieting or in gaining weight. They're usually not the type of losses or gains that you want. Our bodies want to get rid of muscle first because it takes more energy to feed, which is why you'll notice that sprinters look like bodybuilders and marathon runners look like crack whores with love handles. People who use their muscles in an intense way and feed them accordingly are sending a clear message to their body: that they need their muscle, and that they have an ample supply of fuel for them. People who starve themselves or don't use their muscles are sending the opposite: keep the fat, get rid of this muscle. I think that's one of the reasons why weight lifting is so important for athletes: they are plenty of muscles that are not primarily used in most sports that would otherwise atrophy, leading to strength imbalances, then leading to injuries. If you tell your body that you need ALL of them, they'll stay strong. There are other ways to do this, but none as time efficient.