Hi, all. My sister and I have been calorie counting for several months now. She came to visit me, and we stayed on plan for a few days, but by the middle of the week, we'd gone off plan. Now, I'll grant you that my sister did eat plenty of sweets, but I wouldn't classify any day as a pure, blow-out "binge." I'd say that she overate for 5 days, but when I say "overate," I mean that she had some sweets instead of meals rather than in addition to meals (e.g., she ate two big doughnuts and a mocha for breakfast one day). She weighs about 180, so even to maintain her weight, I think she can eat 2000+ calories a day. However, after being on program a couple of days, she weighed herself today and found that she's gained 2.5 lbs. How is this possible? I mean, for her to gain that much, she would had to have eaten more than 8,000 calories over and above her maintenance calories. I know she didn't do that. Can anyone explain this phenomenon? It seems as if it takes an entire week of watching it to lose a mere pound but just a few days of lose eating to gain a few pounds. It's very frustrating!

I think it is a combination of two factors: water and underestimating calories. When I am off-plan, even for just a day, I find that I often retain more water than usual. My body isn't used to eating that way and often reacts to the additional calories, refined carbs, and fat by retaining water. So most certainly some of the gain your sister is seeing is water weight and she'll probably lose it quickly once she is back on plan.

Also, however, when we aren't measuring and weighing everything we eat, we tend to underestimate calories quite a bit. The fact is, doughnuts and mochas are very high calories, probably higher than you think. Two doughnuts and a mocha could easily be over 2,000 calories right there. Unfortunately, it's easy to eat a few thousand calories over your maintenance level, even in just one day. But when you are trying to loss, you can't really average more than a 500-1,000 calorie deficit per day (especially at your sister's current weight). So you can gain faster than you can lose.

So some of the gain your sister is seeing is probably weight that she's gained back. The good news is that if she lost it once, she can lose it again. We all do this from time to time; I can't even count the number of vacations/business trips where I've been off plan, gain a few lbs and had to lose them again. But they always come back off when I get back on plan.

Yep, water is a big culprit with quick weight gain/loss. Especially when eating salty and sugar foods. Both cause water retention. Also, if she's eating junk, she might be constipated. Hopefully by the time the week is up, she'll have been able to break even.

I agree with what was said above. If you see a weight gain or loss that's too big to be believed or to account for with calories, that means it's primarily water weight. There have been a lot of studies of this! The first big loss or gain is mostly water.

Thanks, guys. Barbara, you're probably right about those doughnuts and that mocha. The doughnuts were from some bakery and they were probably double the size of a regular doughnut (they were good, though .

Jennifer, I didn't realize that eating sugar would result in water retention. That might explain a lot (By the way, I love the doggie pictures on your avatar!).

Thanks, Kilketay (we must have postd at the exact same time). By the way, how is Volumetrics working out for you? I think I read somewhere that this was the highest rated diet by Consumer Reports.

Hi Lynn, the sugar causes water retention in the lining of the stomach. The water stores glycogen, which the body produces from sugar. When you cut back on sugary food, your body burns off the glycogen for energy, and the water is 'flushed'. That's why South Beach, Atkins, and even just low cal diets that happen to cut out sugar, promise a big weight loss at the start, or advertise to lose inches on the waist in the first week. Shuga!

Thanks for the nice words for my babies! They were happy from a walk that day. They're our little goofballs!

I love Volumetrics! I'm not following their diet plan exactly, but I'm incorporating the basic principles into my diet. Volumetrics is a system that's based on a lot of research that was conducted by Barbara Rolls as the University of Pennsylvania. Her research shows that eating foods that are less calorie dense (fewer calories per gram) naturally results in subjects eating fewer calories. They feel full on fewer calories.

Even if you never read the book, the takeaway point is to focus on eating foods that are lower in energy density. Energy density is calories divided by grams. An overall energy density below 1 is the goal, but lower is better. Basically, that means that if you're looking at two frozen meals and one has 300 calories for 298 grams and one has 300 calories for 149 grams, pick the first one (energy density is lower, close to 1) rather than the second (energy density close to 2).