For Low Carb Dieters: Water Weight vs. Fat Weight
Don't Be Fooled by Quick Losses and Devastating Gains!
After a week of doing a low carb diet, new dieters are filled with excitement. They've lost anywhere from four to ten or even twelve pounds. They conclude, "This diet works!" and their enthusiasm after that quick weight loss may motivate them to stick with the diet even when the weight loss slows down to normal levels--3 to 8 pounds a month
But there's a dark side to this instant weight loss. Slip up and eat a "normal" diet for a day and what happens? The lost pounds are back, all five or ten of them! The feeling of failure and distress can set the dieter on a spiral of binging and despair that quickly leads to their regaining of all the weight lost through weeks of dieting.
In fact, both the joy and the despair you feel in response to this rapid loss or gain is misplaced. The quick losses and gains are almost entirely water. Whether you are low carbing or not, you must burn off 3,500 more calories than you take in to lose a pound of fat and you must eat 3,500 calories more than you need to gain a pound. Despite the hype in the diet doctors' books, low carbing does not repeal the basic laws of thermodynamics. So what is that four to ten pounds of "easy go, easy come" weight all about?
What you REALLY Lost or Gained
When you cut the carbs out of your diet, your body empties out the "emergency" stores of carbohydrate it keeps in the liver and muscles in the form of a substance called glycogen. Glycogen is a normal part of our metabolism and allows us to do energy-intensive things like sprinting, for example, by letting us draw on the carbs stored in our muscles for energy.
More importantly the glycogen stored in our liver allows us to keep our brain functioning. A person who is not low carbing needs 100 gms of glucose a day merely to supply the brain's basic needs. If the body can't get glucose from the diet it has two choices: use stored carbohydrate--our friend glycogen again, or convert dietary or muscle protein into carbohydrate using a lengthy process called "gluconeogenesis" which takes place in the liver. Because the body wants to avoid using its own muscle fibers for fuel, it does what it can to keep that liver glycogen store filled up.
Medical textbooks usually tell us that a typical 150 lb man is carrying about three quarters of a pound of glycogen, but in my researches for my book Diet 101:The Truth About Low Carb Diets I found some solid evidence that suggests that this estimate only applies to the young, lean, male college students who were research subjects in the 1950s and '60s. If you are overweight, especially if you got overweight eating a diet full of starch, sugar, and high fructose corn syrup, it is very likely that you are carrying a lot more glycogen than that estimate.
And the news gets worse, because it turns out that each gram of glycogen is bound to four grams of water.This means that when your liver and muscles are charged up with glycogen you gain four times the weight of that glycogen in water.
When you start a very low carb diet you cut off the body's supply of dietary carbohydrate and this leads to a rapid emptying of these liver and muscle glycogen stores. And when you lose that glycogen, you also lose the associated water. That's the reason why, during the first couple days of a low carb diet, you lose weight so dramatically. It's also why you may feel slimmer and lose "inches." You haven't lost fat. You've simply squeezed out the water and glycogen in your muscles and liver.
But what happens when you go off the diet for even so little as a single meal? If you eat a significant amount of carbs, your liver and muscles grab glucose from your bloodstream to replenish that emergency stock. As they do this, four grams of water join each gram of glycogen and, as fast as you can say, "Omigawd, I cheated!" the pounds you lost at the very beginning of the diet pile back on.
How Many Carbs Does It Take to Replenish Your Glycogen?
Not too many. If you were only carrying that three quarters of a pound of glycogen the textbook's 150 lb. man would carry in his liver, you'd only need about 70 grams of carbohydrate to start refilling it.
Chow down some french fries and a regular soda and you're there.
Do You Lose any REAL Fat Weight on a Low Carb Diet?
Probably not in the first three days--unless you cut 1200 calories out of your usual diet, too. But once you have gotten through the first week or two another benefit of low carbing kicks in that does make it much easier for most people to cut out the calories they need to cut to lose real fat.
That's because when you cut out your carbs you eliminate the blood sugar swings that cause hunger in most people. The cravings you used to get when dieting may fade out in as little as two weeks. When you stop eating in response to those nasty hunger cravings, you will find it much easier to eat a whole lot less than you used to. It is the drop in calorie intake that follows this drop in hunger that that results in the very real and often dramatic weight loss so many long-term low carbers report.
Will You Gain It All Back when You Go off the Diet?
Many books and experienced low carb dieters warn that low carbing brings with it a "devil's bargain." They tell you that you can lose all the weight you want on their diet but if you do, you must make low carbing a "way of eating" for the rest of your life.
The instant weight regain that low carbers experience tends to confirm that this is true, which can be very frightening if for one reason or another the dieter decides to return to a balanced-type diet.
But it turns out that while it is true that many lapsed low carb dieters DO regain a lot of weight--often ending up heavier than they started, the reason has nothing to do with the fact that they were eating a low carb diet.
The real problem is that eating very low carb diets teaches people to eat a lot of fat, so that erstwhile low carb dieters who go off their diets but keep eating the high fat foods appropriate only to a low carb diet end up boosting their calories. If they don't, once they refill their glycogen and put on the extra water weight associated with it they will not gain any more weight than can be explained by the old, boring equation, one pound of fat = 3,500 calories.
There's plenty of research documenting this, which you can read about in Diet 101: The Truth About Low Carb Diets.
The take-home message from this is if you are eating a very low carb diet you need to remember every time that every time you get on the scale your REAL weight--the weight you will be when you stop dieting-- is whatever you weigh now plus whatever you lost during the first weeks of the diet when glycogen burns away.
If you go off plan for a day, don't panic when you step on the scale. That instant three pounds is only water. Compare what you weigh--with the water--to what you weighed the last time you went off plan. It's less, isn't it? And that is REAL weight loss!
A Last Word for People Taking Metformin
Metformin is a drug that is approved for treating diabetes, pre-diabetes and PCOS. When I started taking metformin, I discovered that if I started eating a very low carb diet I no longer dropped or gained the dramatic amounts of water weight that I used to see without the drug. My guess is that metformin prevents the liver and/or the muscles from storing glycogen. If it does, that would explain why studies show that metformin causes a small weight loss in most people who take it, but only initially.
However, if you stop taking metformin and eat enough food to refill your glycogen, you may find those water pounds packing on very quickly.