I would imagine that the gain over the week isn't so much gain as retained water, which is totally different from the up and down of yo-yo dieting. I jumped up two pounds between Monday morning and Tuesday morning, back down a pound today. I don't think I really gained two entire pounds between Monday and Tuesday, though. I figure you are the same way maybe? Anytime I have one of my high cal days I go over typically in sugar and carbs, which really make me hang on to water like a sponge.

I would think yo-yo dieting impact would have to take longer with a little more spread in the ups and downs?

Yeah, you can't gain 2-4 lb of fat in 2 days without going on Man vs Food. It's just water/sodium/food in your digestive tract.

Good point:)

Honestly, I always weigh more on Mondays even though I eat about the same amount every day. The only thing different is that I don't drink enough water over the weekend. During the week, I drink 2-3 liters a day just sitting at my desk. Weight is SO fickle. I always weigh the least on Fridays too.

Au contraire! It's quite a good strategy and not harmful or bad for your metabolism. I did WW for quite some time and they promoted that method, as do many programs. Have you ever heard that advice, eat healthy 80% of the time and 20% of the time you can relax a bit? That's what you're doing. It's a great strategy and it works for you!

Something to keep in mind

Our daily caloric burn is NOT STATIC.... we dont always burn 1800 cals a day when we dont run for 5 miles at 10 min/miles, and we dont always burn 2400 on days we DO run... get what im saying? I imagin you are more active on the weekends (do you have a deskjob too?).... No single day in our life is going to be the exact same caloric expediture as another day..... if you MOVE MORE and are generally more active on wekends (going shopping, exercising, cleaning the house, ettc) vs weekdays (workout, sit at desk for 8 hours, Cook dinner, go to bed) then you are going to need less cals anyway on weekdays (USUALLY/GENERALLY) i think its perfectly fine to eat lower during the week, and higher during the weekend, and you know another great maintennace tool?
If you "overdo it" one day, its a great idea to have one REALLY low day a week, as low as you can go (even fasting) to offset any overages and make a big dent in your total cal intake

I'm late to the party, but FWIW I maintain that way too. I eat less on weekdays then have my "cheat" meal(s) on the weekend. I'm always about 2lbs heavier on Monday than on Friday. As long as Friday stays the same, it's all good IMO.