Reading Past the Headline: Low Fat vs Low Carb

A recent study purportedly showed that a low-carb diet is superior to a low-fat diet.  However, David Katz explains how this study was flawed.  Here’s the link: Huffington Post “Low-fat” versus Low-carb and here’s an excerpt:

It was published in the Annals of Internal Medicine.. Allegedly, the researchers compared a low-fat to a low-carb diet. But in fact, they compared a diet that allowed up to 30 percent of calories from fat to a diet that allowed up to 40 grams of daily carbohydrate…

baseline carbohydrate intake was 240 grams per day, so while fat intake was “trimmed” 5 percent, carbohydrate intake in that assignment was slashed 75 percent. This might have been billed “a study to compare a really big change from baseline diet to a really small change from baseline diet.”…

the low-carb diet, since it was actually low-carb, obviously was much more restrictive than the low-fat diet, which wasn’t actually low-fat. That had the predictable result: those on the low-carb assignment took in many fewer calories…

I am not an advocate of low-fat diets. I think the concept is obsolete. I am an advocate, based on the evidence, of wholesome foods in sensible combinations. That dietary pattern can be low or high in fat, relatively lower or higher in carbohydrate.

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Six years later-Mediterranean diet comes out on top

This month a followup letter provides long-term data on the outcomes of individuals assigned to either a low-carb, low-fat, or Mediterranean diet (NEJM 2012; 1373-74).

An initial study posted two-year results.  Now after an additional four years, the following results were noted:

  • Among the 259 participants (80% of original groups and 95% who completed the initial two years), 67% had continued their original assigned diet.
  • For the entire 6-year period, the total weight loss was 3.1 kg in the Mediterranean group, 1.7 kg in the low-carb group and 0.6 kg in the low-fat group.
  • At 6 years the change in the ratio of LDL to HDL were similar in all three groups though the low-carb group had the most favorable results with a reduction of 0.16.
  • At 6 years, the reduction in triglyceride levels from baseline were significant for the Mediterranean group (21.4 mg/dL) and the low-carb group (11.3 mg/dL).
  • All of the groups had regained some of their weight loss from the initial 2-year period.  The most favorable outcomes were noted in the Mediterranean diet and then the low-carb diet in this workplace intervention trial.

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