Actually, to take the fact one step further (it's no theory .. this is firmly established in science and FACT ;)) .. it is the absence of INSULIN that makes this possible.
Insulin is required to assist glucose to enter the cells to be used for fuel. If there's more glucose than is required at the moment, then insulin will cause it to be stored as FAT. It will also cause any excess fat from the diet to be stored as fat, since it's not required as fuel (there's already too much glucose). Another role of insulin is to inhibit fat-burning. It prevents the fat cells from releasing their fat stores (both as a biological "conservation" mechanism, and to prevent the fat from competing with glucose as a fuel source).
When you restrict carbohydrates in your diet, you effectively reduce the amount of insulin produced, as your body switches over to burning ketones for fuel instead of glucose. Without so much insulin floating around, your fat cells will be able to release stored fat more easily. Without so much insulin floating around, the fat you EAT will not be stored as fat either.
So what happens to the fat you eat?? Well, some will be used in the repair and structure of cell walls throughout the body, and to make vital hormones. Some may used for energy. The rest is WASTED. That's right, wasted. The fat you eat is broken down into fatty acids in the bowel, by the action of enzymes and bile. These fatty acids are absorbed into the bloodstream and taken to the liver, where they are further processed ... into ketones, and into other fatty acid components. Some of the ketones may be used for fuel. Mostly they are excreted in the urine, stool and breath (via the lungs). Unused free fatty acid components are also excreted. Why?? Because once fatty acids are broken down into the smaller ketone, acetone and fatty esterols .. they CANNOT be converted back into fat. That's basic Biochemistry 101. Without insulin, they cannot be forced into storage in the fat cells. So they are eliminated. This is what Atkins refers to as the "Metabolic Advantage".
My explanation is very simplistic .. there's more involved, such as the release of glucagon from the pancreas, etc ... If you're truly curious about this, we had an excellent discussion a few months ago on this subject. You can read about it
starting here .. it's a long thread, with lots of lofty discussion :read:
What does this have to do with calories and eating fat? Well, when you're wasting fat, you're wasting the potential energy (ie the calories) that it would otherwise provide. Lets look at a sample day's intake:
- 20g carbs (80 calories)
120g protein (480 calories)
120g fat (1080 calories)
total calories = 1660, and 65% of that is fat calories.
However, research shows that by the process of wasting fatty acids, as I described above .. the actual caloric contribution of dietary fat, in the absence of insulin is only about half, or roughly 5 calories per gram. Given that knowledge, lets have another look at the sample day's intake:
- 20g carbs (80 calories)
120g protein (480 calories)
120g fat (approx. 600 calories)
total calories = 1180, of which 51% comes from fat.
There is plenty of evidence to show that consistently eating below a certain caloric level will result in the slowing of the metabolic rate, as an adaptive "survival" mecanism. The body thinks it's starving, so it turns the thermostat down to conserve fuel. Your engines will run on less and less. In other words the less you eat on a continual basis, the less you will NEED on a permanent basis. This will only work against you in the long run, making it increasingly difficult to lose fat weight, and also making it easier to GAIN fat if you return to a carbohydrate & insulin-based way of eating. So eat up, and especially eat FAT :)
The other question is how does eating fat stimulate the burning of BODY fat?? Well, it acts like kindling. It primes the liver into fat-burning and ketone-production mode. Once this ketone production is in full swing, and the dietary fat is used up, the liver starts looking for more source of fat to process. It turns to your body fat stores :cool:.
Hope this is helpful,
Doreen
