Not high fat diet?

[Guest guest]

Hi All,

Do you ever feel " that fat is the bomb and carbohydrate is the fuse " ? CR is the

bomb shelter?

See the pdf-available not yet in Medline and maybe free to all below that

discusses

a similarly hopefully free to all paper.

When is a high fat diet not a high fat diet?

D Feinman

Nutrition & Metabolism 2005, 2:27 (17 October 2005) Editorial No abstract (17

October 2005)

http://www.nutritionandmetabolism.com/content/2/1/27

The observation that a high fat/low carbohydrate (CHO) diet has a beneficial

effect

on a

mouse model of Alzheimer’s disease (AD) published today is notable given

previous

results showing that high fat diets have a deleterious effect on AD. Van de

Auwera,

et al.

[1] reported that mice fed a ketogenic diet (<1% carbohydrate, 80% fat ) were

found

to

have a 25% decrease in the protein Aß42 compared to mice fed a standard high-

carbohydrate, low-fat chow diet. Aß42 is particularly amyloidogenic mutant form

of

the

amyloid precursor protein whose proteolytic product ß–amyloid peptide is

contained

in

the plaques and neurofibrillar tangles that are characteristic of AD.

.... Similarity of starvation and carbohydrate restriction

One of the areas bearing on the idea that disposition of fat is controlled by

insulin is the

observation made by several groups that the metabolic response to starvation

resembles

the response to carbohydrate restriction [7-11]. An important but, in our view,

under-

appreciated study is that of Klein & Wolfe [11] who compared responses of

subjects

on

an 84 hour fast to the same subjects on a similar fast in which lipids were

infused

at a

level equal to resting energy requirements. Table 1 shows that the levels of

fatty

acid,

rates of oxidation and levels of glucose and ketone bodies were similar in the

two

groups

(Table 1). These rather dramatic results were summarized by the authors as

demonstrating that “carbohydrate restriction, not the presence of a negative

energy

balance, is responsible for initiating the metabolic response to fasting.” It

might

be said

that this is the key experiment in understanding the interaction between fat and

carbohydrate. Similarly, Bisschop, et al. [8] demonstrated a similarity between

high

carbohydrate, low fat diets (CHO:Lipid:Protein = 85:0:15) and control (44:41:15)

diets

in FFA rate of appearance and oxidation but significant differences with a low

carbohydrate, high fat diet (CHO:Lipid:Protein = 2:83:15).

High fat diets in obesity

The interaction of fat and carbohydrate bear on the mechanism of weight loss

strategies

based on carbohydrate restriction. In considering the problem, it is important

to

recognize that percentages are misleading. There are really three degrees of

freedom

in

design or analysis of a weight loss experiment: two of the three macronutrients

and

the

total caloric intake. It is unlikely that the percentage rather than the

absolute

amount of

macronutrients is the controlling variable and at least three published studies

show

that

carbohydrate reduction is not necessarily accompanied by replacement with either

fat

or

protein but rather caloric reduction due to the carbohydrate removed [12-14].

Such

diets

are effectively high fat by percentages but lead to substantial weight loss.

To understand the relative impact of carbohydrate and fat, one has to consider

experiments in which one macronutrient is replaced by another. Several studies

in

the

literature have demonstrated that in isocaloric comparisons, the replacement of

dietary

carbohydrate with fat leads to greater weight loss [15-19], that is, the absence

of

the fuse

prevents an explosive effect of dietary fat on body mass. The limitations of the

fat

bomb

per se are reviewed by Willett and Leibel [20].

.... the study of Garg, et

al. [26, 27]. In a four-center randomized crossover trial, carbohydrate was

replaced

with

monounsaturated fats (CHO: 55 % –> 40; total fat: 30% –> 45) or, conversely, MUF

was

replaced with CHO. It was found that replacement of MUF with carbohydrate

“caused

persistent deterioration of glycemic control and accentuation of

hyperinsulinemia,

as well

as increased plasma triglyceride and very-low-density lipoprotein cholesterol

levels,

which may not be desirable [26],” that is, the high fat arm was beneficial,

again,

suggesting that what happened to the fat was more important than its

concentration

in the

diet.

To determine the relative importance of fat and carbohydrate and protein, Gannon

and

coworkers have measured the effect of replacement of carbohydrate with protein

and

fat

in patients with type 2 diabetes [28]. Figure 1 shows the effects on glycemic

control of

the replacement of carbohydrate with protein and fat. Again, the 50 % fat diet

provides

better glycemic control although, in this case, the relative contributions of

carbohydrate

reduction and increase in protein is unknown.

Conclusion

The long range implication of Van de Auwera’s study for AD remains to be seen

but

the

general lesson is that in dietary recommendations or in testing animal models a

diet

should not be characterized as high fat without also specifying the level of

carbohydrate.

1. Van der Auwera I, Wera S, Van Leuven F, ST: A ketogenic diet

reduces amyloid beta 40 and 42 in a mouse model of Alzheimer's disease

2005 Nutr Metab (Lond) 2005. 2

http://www.nutritionandmetabolism.com/content/pdf/1743-7075-2-28.pdf

Al Pater, PhD; email: old542000@...

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