Fat cells are resilient, stubborn little creatures that do not want to give up their actual cell volume. Over a period of weeks, maybe months of "proper dieting", each of your fat cells may have actually lost a good percentage of the actual fat contained in those cells. But the fat cells themselves, stubborn little guys, replace that lost fat with water to retain their size.
That is, instead of shrinking to match the reduced amount of fat in the cell, they stay the same size! Result - you weigh the same, look the same, maybe even gained some scale weight, even though you have actually lost some serious fat.
The good news is that this water replacement is temporary. It's a defensive measure to keep your body from changing too rapidly. It allows the fat cell to counter the rapid change in cell composition, allowing for a slow, gradual reduction in cell size. The problem is, most people are frustrated with their apparent lack of success, assume they have lost nothing, and stop dieting.
However, if you give those fat cells some time, like 4-6 months, and ignore the scale weight fluctuations, your real weight/shape will slowly begin to show. The moral of the story - be patient! Your body is changing even if the number on the scale isn't.
Patterns of weight loss
Common patterns of weight loss from tracking a lot of people who become assimilated into the low carb lifestyle, sees a pattern emerge.... the 2 week induction is pretty heady...weight lost just about every single day, enormous and unbelievable amounts of weight loss are reported. This is often followed by complaints that weight loss "stalls" or that the rate drops to only 500g per week.
Many people just don't know that fat-loss ...the actual goal when on a weight-reduction diet, is rate-limited. In other words, the human body has factors that prevent more than a certain amount of fatty-acid release from storage...and even more factors that prevent those released fatty acids from being used up instead of stored back into the fat cells.
A priority of the human body is survival. Anything that threatens its survival results in the cascade of events to maintain the previous status quo. Water fluctuations are one way the body does this. OK...so you done well on Banting during so... what gives?
Initially, the body jettisons the water attached to the glycogen stores that we diligently deplete to get into ketosis...this accounts for about 1-2kg’s of water. In addition, muscle stores of glycogen are not being replaced when used...which will account for the rest. All in all...MAYBE 1/2 kg of fat was metabolized during the first week... and MAYBE 1/2 kg of fat was metabolized the 2nd week.
The body senses this lack and sirens start shrieking: Warning! Warning! Losing water... new thing...got to get back to the status quo! Brain tells body to produce and release that vasopressin anti-diuretic hormone....more water is retained, and no weight loss noticed. Fat loss is still occurring, because ketosis is firmly established and appetite suppression is in effect...but water retention is hiding that continuing fat loss. The body is preventing dehydration with this mechanism, and that's a *good* thing.
From the perspective of the scale, it can be discouraging. Which is why the mantra: Water retention masks fat loss (repeated frequently to oneself) is helpful. Water retention will mask ongoing fat-loss for as long as the body retains the water. We can combat this by drinking more water...but we aren't going to totally overcome this mechanism during the initial water-loss phase of the Banting diet. By weeks 5 and 6, things start to get back in balance, and the scale will begin to reflect the true fat-loss...which, as mentioned before is rate-limited.
Individuals vary, but max weight loss runs about kg per week...under extremely optimal conditions... or 1% of body weight (whichever is the lower number).