September 6

Score another for the low-carb diet

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A paper appeared in the September issue of the Journal of the American Dietetic Association showing once again the superiority of the low-carbohydrate diet for weight-loss
If you’ve followed a low-carbohydrate diet in the past for any length of time, you can skip this post because this paper won’t tell you anything you don’t already know firsthand.
The researchers randomized overweight, premenopausal women (average age about 40) into two groups, one of which followed a low-carb diet, the other a low-fat, low-calorie diet. Women in the group following the low-carb diet were instructed to limit their carb intake to below 20 grams per day for the first two weeks, then to increase carbs by 5 grams per week, bringing their daily total to 40 grams of carb by the last week of the six week study. Other than this carb restriction, the low-carb dieters were NOT instructed to limit total food intake. The women in the low-fat, low-calorie group were given much more specific instructions; they were to limit their caloric intake to between 1500 to 1700 calories per day (based on each woman’s estimated resting energy expenditure) and to consume these calories as 60% carbohydrate, 15% protein, and 25% fat.
After six weeks on these diets the women following the low-carb diet lost about 44% more weight than those following the higher-carb, low-fat, low-calorie diet.
When we look deeper into the data, the study gets a little more interesting. Although the ladies on the low-carb diet were not instructed to limit their overall food intake, but only to restrict carbohydrate intake to from 20-40 grams per day, their overall caloric consumption dropped to 1420 calories per day. This caloric drop came without trying and mirrors perfectly the old studies from Dr. John Yudkin’s lab back in the 60s and 70s that I discussed in an earlier post. How about the women on the low-fat, low-calorie diet? They dropped their calories to 1395 per day, essentially the same as the low-carb dieters, but they lost less weight.
When Dr. Yudkin did his studies 40 years ago he reported that his subjects on the low-carb diet ate until full and reduced their caloric intake at the same time. So did the women in the present study, which apparently took these researchers by surprise:

It is important to note that women in the low-carbohydrate/high-protein diet group were not instructed to restrict energy intake. Yet, they did.

You can almost hear the gasp.
The researchers gave all the subjects a standard questionnaire designed to determine levels of hunger at the start of the study, at the end of the first week, and at the end of the study. Those women who followed the low-carb diet had less hunger at the end of the first week and at the end of the study than they had before they had begun to diet. Those on the low-fat, low-calorie diet were not so lucky.

The low-carbohydrate/high-protein diet group had a significant decrease (P
I looked through the section on research techniques in this study to see what kind of exercise was recommended but couldn’t find anything about any kind of exercise whatsoever, which is strange since most dietary studies try to control for exercise. To my great amusement it all became clear to me as I read through the discussion section of the paper that the people doing this study were obviously not familiar with low-carb diets and just as obviously had a great deal of trepidation about the entire undertaking. And were a little deficient in basic biochemistry. Here is what caught my eye:

Physical activity was not included as an intervention component for this study because of concerns regarding the low level of glucose provided by the low-carbohydrate/high-protein diet.

Heh, heh, heh.


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