Biochemists argue that food calories are not all equal

[Guest guest]

http://www.nature.com/news/2004/040816/full/040816-2.html

Logan

[Guest guest]

There are reasons " within " the laws of thermodynamics on why sometimes low carb

diets appear to cause more weight loss.. Some of these include...

1) the 4 calories per gram of cho and pro and 9 calories per gram of fat are not

accurate but estimates/averages given to make calculations easier. So, are the

numbers we see on most exercise equipment nothing more than average estimates.

So, it is alwasy very important to see how each study either calculated or

estimated calories in and calories out.

2) gram for gram, protein does raise metabolism ever so slightly more than carb

and both more than fat due to " energy cost " of metabolism.

3) In early stages low carb dieters will lose more weight due to loss of

glucogen and water which can account for 4-6 lbs easily.

More comments...

Feinman is correct about that diets with more protein can increase heat

production and so waste some energy relative to fat and carbohydrate. However,

there are several flaws in his argument. First,his assumption that ketogenic

diets replace CHO with a 50-50 mix of protein and fat is incorrect. The most

popular high protein diet, the Atkins diet would be about 10% CHO, 25% PRO and

more than 60% FAT. Because the SDA or " energy cost " for FAT is less than half

that of CHO this would negate the " metabolic advantage " as the predicted thermic

effect of the two diets is in fact very similar (although the diets would have a

small " metabolic advantage " compared to the typical American diet or the

AHA/NCEP " low-fat " diets) but not to a healthy high fiber, plant based whole

foods diet.

The studies that reported greater weight loss on ketogenic diets did not measure

metabolic rate and did not directly measure fat and total energy stores. Over a

period of a few weeks body weight is not a precise enough measure of body energy

stores to justify any conclusions about the claimed " metabolic advantage " of due

to a higher percent protein in the diet.

If diets with a higher SDA (or SDE) are preferrable for weight loss then the

ideal weight loss diet would be very high in protein with very little fat. Of

course diets very high in protein if widely adopted are not know to be safe and

would dramatically increase the cost of food and have a large negative impact on

the enviroment. Why? The energy cost of producing protein for human consumption

is far greater than that for producing carbohydrate-rich foods like potatoes and

whole grains. I get the feeling that Feinman may be overlooking the energy cost

(to the planet) of wasting more energy by " solving " America's obesity epidemic

by having us eat more protein and less carbohydrate.

the proponets of high protein diets claimed the " metabolic advantage " of their

ketogenic diet came not from the increased thermic effect of protein but by the

loss of energy from the body in the form of ketones. Of course, this turned out

to be less than 50kcal/day for most people.

Also, the results of this small review of 10 (might I say- " hand-picked " )

studies hardly constitute proof that low-carb diets produce greater depletion of

energy reserve than diets higher in carbohydrate despite the same energy intake.

It is true that a few studies have reported such results but all such studies

used free living subjects and we know that accurate measure of energy intake

under those circumstances is problematic.

Of course, in short-term studies changes in glycogen stores (decreased on

low-carb diets) and total body water content (diuresis associated with ketosis)

can produce greater weight loss (but not greater fat loss or depletion of energy

stores) on a ketogenic diet than a low-fat diet higher in carbohydrate.

However,this does not mean it produces greater fat loss. As i said, this can be

around 4-6 lbs.

Third, a much larger and far more systematic review of low-carb diets found that

weight loss was principally due to decreased caloric intake and total calorie

deficit over time and was not not associated with reduced carbohydrate intake.

[bravata DM, et al. JAMA 2003;289:1837].

When a small " study " is published in a lower tier journal that conflict with

much larger studies with better quality

data we should be skeptical. I am not familiar with biochemist Feinman's track

record but his claim that low-carb diets cause the loss of more body fat (or

total energy stores) than an isoenergetic low-fat diet is extraordinary. His

suggestion that the laws of physics would cause us to expect greater depletion

of energy stores on a low-carb than on a low-fat diet are incredible. I know of

no plausible mechanism whereby replacing carbohydrate with fat could somehow

increase energy expenditure. Do you?

Extraordinary claims require extraordinary proof.

[Guest guest]

I think what is extraordinary is your straw man that Feinman made

extraordinary claims about fat at all. In the article, he was only

mentioned as referring to proteins and carbs. :-)

If protein does have a bio-utilization by the body of less calories

than the energy needed to raise 1kg or 1L of water by 1 degree C [the

ivory-tower definition of kcal], then it should be functionally

equivalent in net calories to a low-protein, high-carb diet (both

with identical percentages of fat). In that case, the overriding

question for carbs vs protein would then become insulin modulation

(fat shuttling) rather than thyroid modulation (metabolism).

Increasing protein would just seem to be an indirect/wasteful method

to eliminate/reduce high-insulin carbohydrates.

Logan

--- In , " Jeff Novick " <jnovick@p...>

wrote:

> When a small " study " is published in a lower tier journal that

conflict with much larger studies with better quality

> data we should be skeptical. I am not familiar with biochemist

Feinman's track record but his claim that low-carb diets cause the

loss of more body fat (or total energy stores) than an isoenergetic

low-fat diet is extraordinary. His suggestion that the laws of

physics would cause us to expect greater depletion of energy stores

on a low-carb than on a low-fat diet are incredible. I know of no

plausible mechanism whereby replacing carbohydrate with fat could

somehow increase energy expenditure. Do you?

>

> Extraordinary claims require extraordinary proof.