The good news is that it isn't likely you gained a pound of fat, it's probably all water. You have to consume 3,500 more calories than you burn to gain one pound of fat. So in one day, you would have had to eat at least 5,000 calories to gain a pound of FAT. Water, however, is much easier to gain and you can see a couple of pounds appear magically overnight, lol. If you went off your diet, you probably ate foods that may be higher in sodium than what you were eating on south beach. If you hop back on your diet, you'll probably see the water loss disappear soon with little to no damage done
Also, it's normal for your body weight to fluctuate a couple of pounds anyway , even if you stick to your diet without fail.
Weight loss via low carb diets does come back more quickly than weight loss via low fat diets. South beach isn't really a low carb diet, though, unless you were still in phase 1.
Weight Watchers has the most long term results of any of the popular diet plans. There are no forbidden foods, it's all about portion control. People are more likely to stick with it because they don't feel deprived. According to our diet survey, most people that leave South Beach or Atkins go to Weight Watchers and stay there.
It's also important to note that approx 80% of the people that successfully lose the weight and keep it off long term, didn't follow WW, Atkins, South Beach, or any other specific diet plan. They did their own thing, usually just by practicing portion control and adding exercise. In fact, I'm pretty sure that 95% of the ones that kept it off included regular exercise, so that seems to be the most important key.
It's so easy to think that we need to pick a diet plan, especially since the media is always talking about which diet is hot today. But statistics show that we do better when we find what works for us as individuals.