I have experimented many times with going on and off low-carb. I'm not sure it's an entirely successful experiment, but here's what I've learned (for myself - it may not all be true for everyone).
1. I find that switching to low-calorie, always results in a sudden gain. This used to panic me, but when I understood it a little better, it's not as traumatic. Carb-digestion requires more water to process (someone here once explained the science very well, but I don't remember it well enough to explain it) than protein and fat digestion. As a result, when you switch to low-cal from low-carb, you're body will hold on to a little more water. This isn't fat, but it is a bit disconcerting to see on the scale. For health, I'm not sure if the little extra water is a big deal. I look at it sort of as my low-carb weight is a couple pounds lower than my high-carb weight (if that makes any sense).
2. To lose the same amount of weight, I have to eat far fewer calories on high-carb eating (and high carb eating makes me hungrier). That means that if I'm going to transition to a higher carb rate, I need to be prepared for more hunger, and I need to be prepared to cut my calories more drastically (for me the difference seems to be about 300 - 500 calories - so I usually lose about as much on 1200 to 1300 calories of high-carb as 1800 calories of low-carb.
This probably wouldn't work very well for you, as you're only eating 1000 calories now, so reducing them probably isn't feasible or ideal. However, since you're ok with losing less rapidly or even maintenance, I'd suggest trying to keep your calorie level about the same, and seeing how that works.
3. I find that I have to be much more dilligent about measuring (using a food scale) and food journaling. To a greater degree, I can let hunger guide my eating for low-carb (when I'm only getting carbs from low-sugar fruits and non-starchy veggies) than for unrestricted carb. On high-carb, I'm more prone to nibbling and guesstimating (just one more bite-itis).
If you're ok with maintaining - I wouldn't even worry about the transition pounds of water gain (as long as you're eating about the same calorie level or less than you are now, anything you've gained in the first two days is probably that water differential), because when you return to low-carb, those pounds are going to disappear.
For me, the biggest hurdle is the increased hunger. I find lots of high-volume (from fiber and water) low-cal vegetables helpful.
4. I find weighing daily most helpful, regardless of diet-type (but especially when switching to a new eating plan). I know a lot of people disagree), but I find that I have more control (regardless of carb-level) over my eating when I weigh daily and start off each day reminding myself of my goals. When I change my eating style, weighing more frequently seems to keep me on task better (this may be a personality quirk of mine, though so - for all of this advice, keep in mind what you feel works best for you).
Most of the time, I regret going off low-carb - but life sometimes intervenes and makes Plan A unworkable. Having a Plan B is better than having no plan at all.
Last edited by kaplods; 06-18-2010 at 11:58 PM.