August 2

Protein trumps carbs–again.

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A new study to add to the growing pile showing the superiority of low-carb diets as compared to high-carb diets for weight loss.
In this study appearing in the August issue of the Journal of Nutrition, 48 women were randomized to one of four groups: a high-protein, low-carb group (PRO), a high-protein, low-carb plus exercise group (PRO + EX), a higher-carb, lower-protein group (CHO) and a higher-carb, lower-protein plus exercise group (CHO+EX). All groups consumed roughly the same number of calories, and the groups that added exercise to their diets did a little better than the groups on diet alone, but not a whole lot better. The main engine for the weight loss in all groups was the diet.
As would be expected by those in the know:

Subjects consuming diets with more protein and less carbohydrate (PRO and PRO + EX) lost more total weight and fat mass and tended to lose less lean mass (P = 0.10) than the groups consuming diets with more carbohydrates and less protein (CHO and CHO + EX).

A number of lab parameters were evaluated with some interesting, but not unexpected, results. The subjects in both CHO groups had greater reductions in total cholesterol and LDL cholesterol, whereas the subjects in the PRO groups had greater reductions in triglycerides while increasing their HDL levels, bringing about a substantial decrease in their triglyceride to HDL ratios.
In keeping with what I’ve been harping on in past posts about the mounting data on the superiority of low-carb diets, the authors had this to say in the introduction to the paper:

There is general consensus that the most critical factor in determining weight loss is total energy intake. The ideal balance of macronutrients for adult weight loss remains widely disputed. However, evidence is accumulating that energy-restricted diets with reduced levels of carbohydrates and higher levels of protein are beneficial during weight loss. These studies report that diets with carbohydrate intake 1.4 g/(kg “� d) result in increased weight loss, increased loss of body fat, attenuated loss of fat-free mass (FFM), improved glycemic control, improved blood lipid profiles, and enhanced satiety.

The authors also address the same point I did yesterday about the idiocy of even looking at fat, protein or carbohydrate as a percentage of calories, although they were much more subdued in their commentary:

Dietary outcomes observed in this study raise questions about the relative merits of expressing dietary intakes of macronutrients as a percentage of energy vs. absolute amounts.

They discuss the problems with this approach reducing the actual protein to a sub-minimum RDA level on many low-fat, high-carbohydrate diets. They then address dietary fat as a percentage of total calories:

A similar concern about the percentage of energy vs. absolute amounts exists for dietary lipids. Subjects in the PRO groups reduced dietary intake of total lipids by 30.1 g/d and SFA by 7.5 g/d. However, expressed as a percentage of energy, total lipids account for 31.9% of energy intake and SFA account for 12.4% of total energy. Hence, expressing dietary intakes as a percentage of energy intakes would result in the conclusion that subjects in the PRO groups have dietary fat intakes above current guidelines of the AHA. Contrary to this conclusion, the PRO groups significantly reduced consumption of total lipids and SFA below baseline values and below national averages.

Once again showing, just as the Yudkin study did, that the absolute amount of fat decreases on a low-carbohdyrate diet.


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