Losing 7 pounds in two weeks at your body weight makes a plateau or brief weight gain very likely, this happens all the time. The body gets ahead of itself with waterloss, the gain probably isn't fat, it's a little water rebound. Fluctuations are normal, you need a longer timeline to really see the trend. I do find I can minimize the fluctuations--by pretty much eating the same foods every day, with the same amount of salt, at the same time of day. It gets a little tiresome, I can't really tell whether it improves weight loss or not, but it does seem to make it easier to see. A friend posted this graph in my journal a while back;



I ate pretty much the same amount of fat, protein and carbohydrate up until February 14, that day I made some savoury ribs--so no increase in carbs--and ate more protein than usual, I'm not sure how much. Certainly not enough to gain four pounds of fat. After that, because I guess I was dissatisfied with really predictable weight loss, and I'm a dork I started doing one 24 hour fast a week--and the waters stay choppy from there. A few days after this graph, I started skipping the weekly fast (until Wednesday, because, again, I'm a dork), went back to eating more or less the same amount of fat, carbs and protein every day, and the fluctuations went back to a bare minimum. My bet would be, that trading protein for fat, calorie for calorie, my fat loss probably wouldn't slow down or reverse--but that switching protein up and down day to day would result in greater fluctuations in my water weight than a steady diet would.