This Week in JAMA FREE

The relationship between physical activity dose and fitness is poorly understood. In an examination of this relationship, Church and colleaguesArticle randomly assigned sedentary, overweight or obese postmenopausal women to 1 of 3 exercise groups with an energy expenditure of 50%, 100%, or 150% of the National Institutes of Health Consensus Development Panel recommended physical activity dose or to a no-exercise control group to measure any change in aerobic fitness during the 6-month intervention. The investigators found a graded dose-response improvement in fitness across the 3 levels of exercise training that was similar across subgroups based on age, weight, baseline fitness, and ethnicity/race. In an editorial, LeeArticle discusses the evidence relating to physical activity dose and health outcomes.

Differing physiological characteristics may be an explanation for inconsistent outcomes of dietary interventions for weight loss. Ebbeling and colleagues investigated whether insulin secretion affects weight loss in obese young adults who were randomly assigned to either a low–glycemic load or a low-fat diet. At the 18-month follow-up, the authors found that among participants whose insulin secretion at baseline was above the median, loss of weight and body fat were greater in persons assigned to the low–glycemic load vs the low-fat diet. The low–glycemic load diet was associated with greater improvements in high-density lipoprotein cholesterol and triglyceride levels and the low-fat diet with more improvement in low-density lipoprotein cholesterol levels.

In an analysis of tissue samples from primary sporadic invasive breast carcinomas, Fukino and colleagues tested the hypothesis that stromal cell genomic alterations are related to the clinicopathological features of the tumor at the time of diagnosis. The authors identified 11 markers of genomic instability on 7 chromosomes in tumor stromal cells that were associated with tumor grade and the presence of regional lymph node metastases. In tumor epithelial cells, 2 markers of genomic instability located on 1 chromosome were associated with progesterone receptor status.

Concern about ethical and scientific problems that might arise from the incomplete or delayed reporting of the results of clinical trials has led to the development of Web-based publicly available clinical trial registries. In an analysis of data from the largest trial registry, ClinicalTrials.gov, Zarin and colleagues review the current status of trial registration and discuss the challenges in developing a comprehensive system for trial registration and reporting of results.

Mr A, a 68-year-old man with severe chronic obstructive pulmonary disease (COPD), coronary artery disease, and other cardiac risk factors including ongoing tobacco use, needs surgery for presumed colon cancer. Smetana discusses patient- and procedure-related risk factors for pulmonary complications after surgery and the evidence supporting pulmonary risk reduction strategies.

A newly discovered common genetic variant could play a major role in predisposing some individuals to obesity and type 2 diabetes.

What cannot be said about health care in the United States.

Advice for giving and receiving effective mentoring.

Introducing JAMA's contributing writers.

Join Jan L. Brandes, MD, Wednesday May 16, 2007, from 2 to 3 PM eastern time to discuss sumatriptan-naproxen for acute treatment of migraine. To register, go to http://www.ihi.org/AuthorintheRoom.

Dr DeAngelis summarizes and comments on this week's issue. Go to http://jama.ama-assn.org/misc/audiocommentary.dtl.

JAMA Theme Issue on Malaria

For your patients: Information about preparing for surgery: evaluating lung function.