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Why a Low-Carb Diet is Best for Weight Loss
How many of you are now more overweight than you were when you started your first weight loss diet?
Does this sound like you?
You have cut the calories, trimmed all the fat off, taken lots of exercise — and now, several years later, you are heavier than you were when you went on your first low-calorie diet.
If it does, then there is a very good reason for this state of affairs; a very good reason why eating less and exercising more, actually puts weight on in the long term: we are programmed by our evolution to store fat against times when food is in short supply. So any low-calorie diet is going to make your body want to conserve energy. And as soon as you eat more it will store any excess as body fat in case of other lean times to come.
Don't starve!
If you are overweight, what is it that you actually want to lose? A silly question, you might think; the answer is simple: you only really want to lose fat. Right?
The point is that, to lose fat, you must get your body using that fat as a fuel; there is no other way. And the only way your body will use its stored fat as a fuel is if you force it to; and the only way to do that is to deprive it of glucose so that it has no choice in the matter.
There are two ways to cut your body's glucose supply: you either starve, which is what low-calorie dieting is, or you reduce just the carb content and make it up with fat. This latter approach has two advantages over the traditional calorie-controlled approach: it means that you no longer have to go hungry and, by feeding your body on fats, it will stop trying to find glucose and change over naturally to using its own stored fat. This is by far the easiest way.
Exercise won't work — unless you eat a low-carb diet
Those who are overweight are usually told that they must exercise to lose fat. Here is why that won't work — unless you also eat a low-carb diet.
As well as storing energy as fat, your body also stores some as a form of starch called glycogen. Because the bloodstream can only hold a very limited amount of glucose, glycogen provides a ready supply of glucose for when the glucose in your blood runs low. Your body stores around 2,000 to 3,000 calories in this way and, significantly, it will use this before it starts to use your body fat.
Let me put that in the context of exercise. If you walk a mile, you will use about 80 calories. So, if walking is the exercise you take, you will need to walk at least 25 miles merely to exhaust your glycogen stores. You will have lost weight because each gram of glycogen is stored with 3 grams of water, but you will not have lost any fat yet.
After such a walk, it is inevitable that you will be hungry and will eat again. If you eat a carb-based meal or a sweetened fizzy drink or fruit, that will top up your glycogen stores again — and you will be right back to square one: the same weight you were before you started that exercise.
(You will also have increased your chances of developing diabetes and other conditions, but that is another story.)
Conclusion
As I said above, if you want to lose fat, your body has to burn it. You can lose it with exercise only if your body has little reserve of glycogen. This means not providing it with the glucose from carbs or protein needed to make that glucose. You can do this either by starving or by eating mostly fat.
Or, of course, you could take up marathon running. The choice is yours.
Last updated 23 January 2004
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