Can someone explain this to me?
"I am interested in the details of one piece of supporting evidence for the bias in favor of carbs over fats for weight loss: the energy density. Everyone uses the energy per gram to argue that carbs should be more filling with fewer calories, by a factor of about 2.
On the other hand, it seems to me that the stomach does not weigh its contents, but might be sensitive to its volume. So we should ask what is the energy content per unit volume of food, not per gram.
So we want to know the grams per cc of fats vs sugar. Anyone with experience in a kitchen will know that when sugar is added to water it sinks, while fat of any type floats, so we know sugar is denser. A little poking around on the internet shows the volume density of sugar is about 1.5, while fats come in at around 0.92. Thus, though fats have twice the energy per gram of carbs, they have only 60% of the grams! This means that fats have only about 20% more energy per unit volume than carbs, in the lab.
In the stomach sugar dissolves while fats donít. Thus the energy density difference per unit volume between them in the stomach is probably negligible.
To me, this argument dissolves any presumptive justification against a high fat diet for weight loss."
Okay, okay... I'll give it a shot.
It seems to me that whoever wrote it is using the "volumetrics" philosophy. That foods that take up more space are more filling. I'm not totally sure, but I think it's more complicated than that.
It is more complicated than that. There are hormone receptors that tell you when you're full. IIRC they are sensitive to fat, fairly insensitive to carbs, and deadened by corn syrup.
(I am not a doctor, I do not play one on TV, I did not stay at a Holiday Inn express last night and I coulda had a V-8 . . . .)
"Filling" has more to do with leptin signaling than volume. While low levels on insulin like those from amino acids and non-starchy vegetables can stimulate insulin, high levels of insulin inhibit leptin signaling. I think that fat potently stimulates leptin signaling but don't quote me. It certainly does something to reduce appetite.
The premise that we feel full when our gut is physically fuller is unsubstantiated. People stay fat by trying to reduce complex chemistry to layman's terms. I don't even fully understand the whole story. Maybe someone else can go into more detail?
Energy density of food is only relevant if you are working to the calorie in/calorie out model of weight loss. The assumption is that a food providing more energy (e.g fat) will put on more weight than a food that provides less (e.g carbs). If this were all there was to it then yes a diet in carbs would be best for weight loss. Is the author of the quote saying that his reasoning regarding volume argues against the favouring of carbs for weight loss? If so, I think he is correct, but not for the reason he states.
When it comes to energy balance the body adjusts to the level of energy in and out, so it is not really the energy value of the food that puts weight on (or helps to lose it). It is a function of the metabolic system as described by Taubes, and a number of other writers, i.e. the action of hormones, that allows the loss of fat on a low carb diet.
Last edited by jo; 04-01-2010 at 01:34 PM.
ahhhh gotch guys thanks!!!!