Whoosh Effect (LTDFLE): Can You Lose Fat But Not Weight?
So one day I was sitting around the old internet listening to stories of epic workouts and 20,000 calorie eating challenges when something new and scandalous hit my ears:
A fat cell may lose fat while at the same time pulling in water. This means that while you may be losing fat, the scale wouldn't immediately reflect it.
Eventually, a fat cell would be allowed to flush the water as the body realizes that this cell will not - in the immediate future - be needed to store fat. Fat cell water is then set free, so to speak.
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This is the claim, but is it a real occurrence? Can the scale temporarily remain stubborn while you are actually dropping fat?
LTDFLE - Long-Term Delayed Fat Loss Effect
This purported process is called LTDFLE, or Long-Term Delayed Fat Loss Effect. Obviously, just because a thing is called a thing doesn't make it a real thing. Right?
So is this phenomenon a real thing?
Lyle McDonald describes LTDFLE as follows:
"Basically, this is the phenomenon whereby fat loss continues to occur even after the diet has been ended and/or calories have been raised back towards/to maintenance or even above. In the same way that fitness sometimes continues to increase after the period of heavy loading, it’s almost as if there is some type of fat loss inertia whereby the diet continues working even after the person ends it." 
The "whoosh effect" was first noted was back in the 90s. A four-week fat loss study found that individuals continued to lose weight during week five, despite an increase in calorie intake towards maintenance level.
While this seems like some next-level wizardry, we can logically and rationally conclude that this continued weight loss must in some way be tied to water retention and subsequent water loss.
Most experienced fat loss coaches know just how much daily water weight fluctuations can spook a client. Well, the reverse is happening here. The individual is eating more but still losing. Instead of feeling spooked coaches hear:
"Hey, my metabolism is on fire!"
Whoa, not so fast.
A liquid gallon of water weighs approximately 8.34 pounds. It only takes about eight ounces of water to mess up your scale weight by a half-pound.
Minor dietary changes in electrolytes, carbs, calories, etc. can lead to small changes in scale weight. Basically, even though your calorie intake remains the same, the human body is so complex that your weight can jump all over the place.
In the short term, that is. In the long term, your weight will always trend down while in an appropriate calorie deficit.
That Wacky Guy Named Cortisol
Cortisol can also mess with water retention. A reduction in training or an increase in calories and/or carbohydrates can slow down the release of cortisol. When this happens - bam - water is released.
Obviously eating more and exercising less is not a long-term plan; this is simply a short-term phenomenon.
The problem here is that water loss is more immediate, and not the more extended loss that was noted in our mysterious study from the 90s. So what's up with that?
Let's keep digging.
Elevated cortisol levels can create a degree of leptin resistance in the human brain. Disrupting proper leptin signaling can be disruptive to the metabolism, and of course, possibly impact water retention.
One of the lessons here is that too much cardio can be disruptive to fat loss. Basically, it can slow your metabolism and potentially lead to some (varying degrees of) water retention.
All this is good and well, but I'd like to get back to the idea that a fat cell can lose fat, pull in water, and mess with your scale weight.
From Fatty Cell to Water-Holding Fat Cell?
The rate of fat loss is not always smooth, steady, and continuous. There are bumps (and mental bruises) along the way.
There is some very minor research that supports the idea that fat cells may turn into water-holding cells. The alleged mechanism goes something like this: When a fat cell empties itself of triglyceride stores (stored fat) the cell temporarily holds water.
Stated more plainly, it may be part of the process that as triglycerides are released, water may be retained in the cell. But again, the research backing this is minimal and certainly not conclusive.
An interesting aspect of this discussion is tied to glycerol. Triglycerides are actually tri-esters; or glycerol that is attached to three fatty acid molecules. During lipolysis - which is basically the process by which the body uses to turn stored energy into usable energy - triglycerides are converted into glycerol and a trio of fatty acids.
Triglycerides can't escape a fat cell until they are broken down. This temporarily leaves glycerol in a fat cell. Glycerol eventually enters the bloodstream but let's pause that thought for a moment.
Glycerol has been documented to increase water concentration in the body. [2,3,4,5] A heightened concentration of glycerol in the body could potentially trigger temporary water retention. This could - could - be occurring in fat cells. Once the glycerol is removed, the water would be flushed. This is the concept, at least.
Again, referencing Lyle McDonald: 
"Back during my college days, one of my professors threw out the idea that after fat cells had been emptied of stored triglyceride, they would temporarily refill with water (glycerol attracts water, which might be part of the mechanism).
So there would be no immediate change in size, body weight or appearance. Then, after some time frame, the water would get dropped, the fat cells would shrink."
Glycerol supplementation or intake has been shown to decrease urination volume and increase hydration.  Prolonged fat loss would obviously result in elevated glycerol levels in the body, but could the processing and trend towards overall water release be cyclical and at times stubborn?
One would think this is a possibility, given the complexity that the human body is.
So is glycerol production during fat loss the cause of temporary water retention? I'm not certain. I would speculate, based upon the myriad of variables, that for some yes and for others no - and this could sometimes be yes and no for the same individual.
Lyle McDonald believes, as I do, that there is a strong chance fat cells may hold water after lipolysis, or the release of triglycerides for energy. Why? Efficiency; to make it as easy as possible for the fat cell to restore energy as fat, which is its current state of affairs.
The mechanisms of the body very rarely flip back and forth between extremes. There is often a transitional, more fluid and cyclical period based upon tendencies and new influencing factors.
It makes little sense for the human body to be reactionary to new stimuli, changes in the environment, and for that matter dietary changes. For example, if someone is in the midst of a long-term feeding frenzy and has been storing fat like mad, it makes no sense for the body to instantly become a fat-burning machine after one day of a minor caloric deficit.
If it is nothing else, the human body is a tool of efficiency. To be the opposite of efficient would be wreckless, wasteful, and damaging to the evolution and survival of the species.
Therefore, we can postulate that a fat cell would also express the same tendency towards efficiency. It is within possibility that the human body would have a reason to maintain the size and girth of a fat cell in the likelihood that it was needed - in the very immediate future - to once again hold fat.
Why wouldn't the body believe this cell was needed? You've been gobbling and gluttonizing for years.
What Happens When a Fat Cell "Deflates"
When you lose weight, what exactly happens to a fat cell? That's the next obvious question. It would eventually shrink, right?
That's the goal after all.
During weight loss, a fat cell will burn through triglycerides. We have established this. But what does a fat cell look like, and what does it look like post-weight loss?
Well, for starters a fat cell is a round and bulging collection of triglycerides. Fat cells are easily created.
"...we found that this fat-producing response occurs unbelievably quickly...” - Matthew Rodeheffer, Yale assistant professor of comparative medicine and of molecular, cellular, and developmental biology. 
While weight gain is driven by the creation and expansion of fat cells, weight loss will not eliminate these newly formed cells. Fat cells merely shrink. They do not die off. This would be an inefficient process for the body.
Imagine if the body had to create an entirely new cell every time it needed to store fat. Instead, it will resort to only creating new cells when needed. The old fat cells remain, waiting for you to gobble up more deadly goodies and fill them back up with triglycerides.
An empty cell still functions. It has a membrane, nucleus, and guess what? A fat cell contains water. A fat cell does not completely deflate like a balloon. Instead, it shrinks but still remains a functional cell.
It is appropriate to view a fat cell like it was a balloon. A fat cell will expand to accommodate energy reserves and shrink upon depleting them.
The average adult fat cell weighs in at about 0.6 micrograms. When overweight, these cells can expand to about three times this size.
Imagine if you will being a fat cell. Food consumption pushes you to the limit; the cell's membrane expands. At its limit, a cell membrane can become compromised and actually leak fat, but this typically only occurs in the morbidly obese and is a topic for another article.
For the record, fat cell leakage can also slow your metabolism: "Overcrowded adipocytes secrete excess adipokines and cytokines under stress, which results in a deregulated metabolism." 
As you lose weight, the cell now exists with an expanded membrane but fewer stored triglycerides.
Is it possible for a reasonable period of time this energy-withdrawn fat cell may hold some extra water to maintain cell and membrane integrity? That is the question of the day.
To my knowledge, we do not know for certain, but can only speculate. Given the body's tendency to remain efficient.
We do know that a fat cell's membrane changes as it expands and when it contracts:
"...a decrease in lipid content was accompanied by the formation of complex frond-like cytoplasmic processes and of loops and folds of basement membrane which extended from cell surfaces. These changes, evident after 1 day of fasting, increased in magnitude with increasing weight loss. As the lipid content of the cell decreased further, lipid-cytoplasmic interfaces became irregular and convoluted. Cytoplasmic microvesicles were prominent and appeared to be greatly increased in number. Rosette-like structures composed of microvesicles were observed in both lipid-depleted fat cells and endothelium." 
That's some serious science-speak, to say the least. The overarching point I'm trying to make here is simple: The expansion and contraction of a fat cell isn't as basic and simplistic as we conjure it up to be in our small mammalian brains.
With all that's going on during fat loss, is it possible that a fat cell might possibly hold a little extra water to assist in fortifying its existing structure and membrane state?
I think so.
Maybe in varying degrees and under varying circumstances. There is so much going on in a fat cell that we can't rule out the possibility.
With all this said, there may be a possibility that at times the body may be holding a little extra water within fat cells - while your scale weight remains steady.
Let's Get Back to Whooshing
There are so many other possibilities to consider, though, when the scale remains steady for a few days. The human body is a complex hormonal dance, ebbing and flowing in such a way as to remain completely unpredictable in the short-term.
The very act of eating less is stressful. Here we return to the nasty subject of cortisol again.
A long-term calorie deficit is obviously stressful in a myriad of different ways. Physically. Hormonally. Emotionally. Etc. This long and winding road of blood, sweat, and tears could certainly result in wacky and seemingly random spikes and dips in cortisol levels.
The result? Cortisol-driven water retention and/or flushing. 
How, back to "whooshing."
A study of 27 men found that during the weight loss process they appeared to be gaining (GAINING) water weight in their fat cells.  Subject weight loss was around 14.5% of overall body weight.
So, this sounds hopeful and conclusive, right?
Nope. Here's the interesting part.
Subjects retained this water weight in their fat cells during a complete year of follow-up visits and analysis. There was no whooshing, in the short or long term. What happened after a year, we do now know.
This might sound like the death knell to the theory of short-term water retention and whooshing in fat cells, but not so fast. Even though long-term water retention was experienced, we can't rule out the possibility in the very short term that fat cells may sponge up a little extra water than normal, and flush a small bit of this out.
This is certainly not unreasonable. Note that I did not claim this to be a certainty.
Outside of the study I just quoted there isn't much in the way of research on this topic. More is certainly needed.
The Finish Line
This is a complex topic. There are some very intelligent individuals that believe fat cell water retention and whooshing is in no way possible.
Then you have obesity coaches that work in the trenches and have experienced many crazy, crazy things. Clients, for no apparent reason, will hold weight for several days and then "whoosh" it out.
Just like chasing bigfoot or UFOs, we'll keep chasing the root cause behind whooshing. The truth is out there, but the truth is likely derived from several dependent or independent factors.
At the end of the day the complexity that is weight loss much be returned back to common sense. Eat better. Move more. Don't abuse your body or seek extremes.
Sleep more, remove stressful people and circumstances. have more sex. Lighten up. Enjoy the ride; just in moderation and not every single day.
1) Lylemcd. "The LTDFLE." Bodyrecomposition, 11 Feb. 2010, bodyrecomposition.com/fat-loss/the-ltdfle.html/.
2) Riedesel, M.L., Allen, D.Y., Peake, G.T., Al-Qattan, K. (1987). Hyperhydration with glycerol solutions. Journal of Applied Physiology, 63, 2262-2268.
3) Latzka, W.A., Sawka, M.N., Montain, S.J., Skrinar, G.S., Fielding, R.A., Matott, R.P., and Pandolf, K.B. (1997). Thermoregulatory effects during compensable exercise-heat stress. Journal of Applied Physiology, 83, 860-866.
4) Montner, P., Stark, D.M., Riedesel, M.L., Murata, G., Robergs, R.A., Timms, M., Chick, T.W. (1996). Pre-exercise glycerol hydration improves cycling endurance time. International Journal of Sports Medicine, 17, 27-33.
5) Freund, B.J., Montain, S.J., Young, A.J., Sawka, M.N., DeLuca, J.P., Pandolf, K.B., Valeri, C.R. (1995). Glycerol hyperhydration: hormonal, renal, and vascular fluid responses. Journal of Applied Physiology, 79, 2069-2077.
6) ---. "Of Whooshes and Squishy Fat." Bodyrecomposition, 15 Nov. 2015, bodyrecomposition.com/fat-loss/of-whooshes-and-squishy-fat.html/.
7) "How to Lose 30 Pounds in 24 Hours: The Definitive Guide to Cutting Weight." The Blog of Author Tim Ferriss, 18 Jan. 2008, tim.blog/2008/01/18/how-to-cut-weight/comment-page-2/.
8) "Study: New Fat Cells Are Created Quickly, but Dieting Can't Eliminate Them." YaleNews, 23 July 2018, news.yale.edu/2015/03/02/study-new-fat-cells-are-created-quickly-dieting-cant-eliminate-them.
9) "Total Control of Fat Cells from Adipogenesis to Apoptosis Using a Xanthene Analog." PubMed Central (PMC), www.ncbi.nlm.nih.gov/pmc/articles/PMC5459503/.
10) JCB | The Journal of Cell Biology, jcb.rupress.org/content/jcb/20/1/57.full.pdf.
11) Rudy Mawer, MSc, CISSN. "13 Easy Ways to Lose Water Weight (Fast and Safely)." Healthline, www.healthline.com/nutrition/13-ways-to-lose-water-weight.
12) Laaksonen DE , et al. "Changes in Abdominal Subcutaneous Fat Water Content with Rapid Weight Loss and Long-term Weight Maintenance in Abdominally Obese Men and Women. - PubMed - NCBI." National Center for Biotechnology Information, www.ncbi.nlm.nih.gov/pubmed/12833111.