PrimeCuts: This Week in the Journals

March 2, 2009

pyramid.jpgCommentary by Michael Tanner MD, Section Editor, Clinical Correlations

Michael Pollan wrote last year in In Defense of Food: An Eater’s Manifesto, “…the history of modern nutritionism has been a history of macronutrients at war: proteins against carbs; carbs against proteins, and then fats; fats against carbs.” This week’s New England Journal features an attempt at a fair fight: a trial that randomized 811 adults with BMIs from 25 to 40 to one of four reduced-calorie diets with the following percentages of macronutrients:

Fat     Protein   Carbohydrates
20        15          65
20        25          55
40        15          45
40        25          35

The diets were not named. Patients’ daily calorie intake was targeted at a deficit of 750 kcal, based on activity level and basal metabolic rate. The trial lasted for two years and found that all four diets produced roughly the same amount of weight loss at six months (6kg) and at two years (3 kg). Participant satisfaction with the diets was similar. The nutrient goals were only partially met; participants randomized to high-protein and low-fat diets found it harder to adhere. The bottom line is that motivation and number of calories mattered more that the composition of a given diet. The trial supports Pollan’s denunciation of the ideology of nutritionism: “there is no imperial nutrient.”

A commentary in this week’s JAMA advocates “more careful, cautious, evidence-based” prescribing practices. It sets forth twenty-five principles of conservative prescribing under six general categories:

Think beyond drugs
More strategic prescribing
Heightened adverse effects vigilance
Caution and skepticism regarding new drugs
Shared agenda with patients
Weigh long-term, broader impacts

The article provocatively suggests that “clinical inertia” may sometimes be a good thing. And there is one real zinger. Citing publication bias and the influence of the drug industry on study designs, the authors write: “The published medical literature is a minefield deterring conservative prescribing.” The article packs a lot into three pages and is well worth reading.

This week’s Lancet features a risk score for developing atrial fibrillation. The authors analyzed the records of 4,764 Framingham cohort patients examined from 1968 to 1987. Ten percent of them developed atrial fibrillation. Age, body-mass index, systolic blood pressure, treatment for hypertension, PR interval, heart murmur, and heart failure make up the seven risk score items, which are readily accessible to primary care physicians. A score of >=10 implies a >30% 10-year risk. Heart failure at an early age (45-54) counts for 10 points all by itself.  The authors estimate that, because of the aging of the population, the current number of two million Americans with AF could rise to as many as 15.9 million cases by the year 2050. Identifying patients at high risk could aid attempts at prevention.

An article in the March Diabetes Care reported a subgroup analysis of the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study, originally published in 2005. The >80% of the 9,795 FIELD diabetics with the metabolic syndrome had a very high risk of cardiovascular disease (17.8% over five years). Not surprisingly, the benefit of fenofibrate was greater in this high-risk group than in the group overall, with a number needed to treat of 23 for the primary outcome of cardiovascular death, MI, stroke, and coronary and carotid revascularization.

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