Help me understand my body and weight loss.
July 2, 2014 8:38 AM   Subscribe

I weigh myself every weekday at work on the same scale (an electronic medical-grade scale they use for patients at the hospital where I work) and at the same time of day. I have noticed that when I go off my diet for a few days and my weight creeps up, that that excess weight falls off again when I return to my diet much more quickly than the weight I've been carrying for awhile. Why?

I've been dieting earnestly for about four months and have lost 20 lbs (yay!). I'm aiming for a 5,000 calorie deficit every week so I'll lose about two pounds, though some weeks I'm more successful at that than others, and I have two cheat days/week, never back-to-back, when I try to eat at least 2,000 calories (but not much more than that) because I've been told my body could get used to the lower calorie amount if I eat that way every day. I'm also eating very healthy on a diet recommended by my doctor and tracked by a dietician every month, and I exercise a lot, so this isn't just a calorie restriction diet, but the calorie restriction part is what's helping me lose weight.

My exercise is logged automatically by my fitbit which is also where I log my calorie consumption, so my calorie deficit is based on the fitbit app's calculations for resting calories burned + exercise calories burned - calories eaten. On the weeks where I have a 5,000 calorie deficit, I lose just about exactly two pounds. It's very predictable.

However, when I go off the diet and gain some weight, if I start dieting immediately afterwards again, the extra weight I just gained goes away again much, much more quickly than the calories in/calories out rule-of-thumb I'm using predicts they should.

For instance, last weekend I went on a four-day weekend vacation and ate all the things (doughnuts, ice cream, etc) and didn't track my intake or weigh myself at all. When I weighed myself Monday morning, I'd gained 3.8 pounds from the previous Wednesday. Yesterday, the gain was only 2 lbs (that is, 1.8 lbs down from Monday). When I weighed myself this morning, I was basically back down to my pre-vacation weight (overall, I've gained a fraction of a pound which I expect to be gone by tomorrow).

I absolutely didn't have a nearly 10,000 calorie deficit in the past two days! Which is what I'd normally need to have to lose four pounds. I ate about 1,000 calories Monday and 1,300 calories Tuesday, and did moderate walking-type exercise, about 6,000 steps/day. According to the 2,500 calories = 1 lb rule-of-thumb that works so well for me normally, this should be impossible, but I notice it happens all the time IF (and ONLY IF) I lose the weight within less than a week of gaining it. It's like that weight is not as "sticky"...

I'd love to understand what is going on here. I know our bodies are more complicated than the calorie in/calorie out thing, and I'm certainly delighted that I don't have to work as hard to lose this weight as I normally do, but my knowledge of physiology is kind of lacking. I only have grade ten biology but can generally follow complex medical explanations. Can somebody who understands what's happening here break it down for me?
posted by joannemerriam to Health & Fitness (10 answers total) 14 users marked this as a favorite
Best answer: Are you male or female? Women tend to gain water weight more easily than men, and can naturally flux a few pounds either way without the weight being "gained" or "lost" per se. Eating junk food causes water retention, so what you are likely seeing is the increased water retention and quick loss as you eat healthy again.
posted by DoubleLune at 8:43 AM on July 2, 2014 [4 favorites]

Water! When you eat all of those delicious treats your body retains water - either through extra salts, or inflammation from sugars. So when you return to your healthy eating your body returns to it's lessened water weight within days.

Try weighing yourself on the same scale at the beginning and end of a shift, or something like that. I can vary several pounds within the same day.
posted by ldthomps at 8:44 AM on July 2, 2014 [5 favorites]

Weight loss is not linear. Sometimes you do everything right and maintain—or even gain. Others you lose a whole lot for no apparent reason. (I've heard this called a "whoosh.")

And your gain after eating all the foods is mostly water & glycogen, which readily comes back off.

2 lbs. per week is a healthy loss for those who are at least 100 lbs. overweight. Depending on how far you are from goal, a healthy loss is anywhere from .5–2 lbs. per week.
posted by editorgrrl at 8:45 AM on July 2, 2014

Best answer: I'm not an expert by any means, but I can tell you the same thing happens to me. The key to it seems to be that the short-term weight gain isn't in the form of putting on extra fat (at least not entirely). There's the weight of the food itself that is still "in transit", which can be more after a big meal or two.

And there's weight associated with water bound to carbs, or so it seems to me. Being diabetic, I check my blood sugar frequently, and whenever it's too high my weight also goes up a few pounds, and when it comes back to normal, the weight goes away again. I conclude it's water weight because the manner in which it escapes is fairly evident. ;)
posted by FishBike at 8:47 AM on July 2, 2014 [2 favorites]

I'm the same way, and the best I can figure is that the lbs gained/lost are found in water weight, and then in the food itself, if it hasn't all moved through your, er, tract yet.

Another consideration, if you're weighing at work, is clothing and shoes.
posted by magdalemon at 8:47 AM on July 2, 2014

Best answer: The quick fluctuations in weight you're experiencing are due to fluctuations in glycogen and water. Glycogen is the body's stored form of carbohydrate. Glycogen is stored largely in the liver and skeletal muscles. When you reduce calories, especially from carbohydrates, your body's glycogen stores will be lower. Glycogen binds with water at a ~1:4 ratio, so when you lose glycogen you lose water as well. This is part of why weight loss is most rapid at the beginning of a diet, particularly on carbohydrate-restricted diets.

Here's a relevant PDF from the American Journal of Clinical Nutrition: Glycogen storage: illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition

The energy balance equation -- calories in vs. calories out -- will always be true, but it's often more complicated than it seems and difficult to determine with accuracy.
posted by ludwig_van at 8:51 AM on July 2, 2014 [12 favorites]

In addition to the glycogen mentioned above, bad foods tend to be higher in salt which will cause you to retain more water and if you're eating more, you have a greater mass of food and waste in your digestive tract. So yeah, its mostly water weight with a little bit of extra poo.
posted by missmagenta at 9:39 AM on July 2, 2014

Best answer: I agree that water is the main culprit here - those sugary, salty junk foods make your body hold onto water. But I bet some of it is also, um, poop weight? Like, if you went a little crazy and ate a lot of food, some of that food is still in your digestive tract. Until you poop it out.
posted by mskyle at 9:39 AM on July 2, 2014

This happens with me. My body is generally a machine calorie-wise and I notice this same effect. I think it's two things.

1. Water weight because the off-diet food is saltier usually. I also feel sometimes that eating a lot of meat makes me feel "puffier" and I am never sure why this is but I notice it

2. Mass of stuff in your gut. For me when I'm eating whatever-levels of food, I am just eating more food, period. So there is more food inside me, more food not pooped out, more food hanging out = more weight.

I get the same thing happening when I've been traveling. Not only am I eating differently but I am also a little dehydrated and travel-constipated and it can take a few days for things to balance out again. I found best results weighing myself first thing in the morning and that gave me a more stable reading. Alternatingly weighing myself every few days so I didn't see (and get confused by) daily fluctuations. And now I've learned a bunch about glycogen, neat!
posted by jessamyn at 10:26 AM on July 2, 2014 [1 favorite]

Response by poster: Thanks, everybody! This all makes perfect sense. (DoubleLune, I'm female.)
posted by joannemerriam at 5:48 PM on July 2, 2014

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