Total amount of exercise important, not frequency, research shows

A new study by Queen’s University researchers has determined that adults who accumulated 150 minutes of exercise on a few days of the week were not any less healthy than adults who exercised more frequently throughout the week.

Ian Janssen and his graduate student Janine Clarke studied 2,324 adults from across Canada to determine whether the frequency of physical activity throughout the week is associated with risk factors for diabetes, heart disease and stroke.

“The findings indicate that it does not matter how adults choose to accumulate their 150 weekly minutes of physical activity,” says Dr. Janssen. “For instance, someone who did not perform any physical activity on Monday to Friday but was active for 150 minutes over the weekend would obtain the same health benefits from their activity as someone who accumulated 150 minutes of activity over the week by doing 20-25 minutes of activity on a daily basis.”

Physical activity was measured continuously throughout the week by having research participants wear accelerometers on their waists. Accelerometers are tiny electrical devices (about the size of a small package of matches) that record how much a person moves every minute.

Dr. Janssen divided the adults who met the physical activity guidelines (more than 150 minutes per week of aerobic activity) into those who were frequently active (active five to seven days of the week) and infrequently active (active one to four days of the week).

“The important message is that adults should aim to accumulate at least 150 minutes of weekly physical activity in whatever pattern that works for their schedule.”

The paper was published today in Applied Physiology, Nutrition and Metabolism

Eating more red meat associated with increased risk of Type 2 diabetes

Eating more red meat over time is associated with an increased risk of type-2 diabetes mellitus (T2DM) in a follow-up of three studies of about 149,000 U.S. men and women, according to a report published Online First by JAMA Internal Medicine, a JAMA Network publication.

Red meat consumption has been consistently related to an increased risk of T2DM, but previous studies measured red meat consumption at a baseline with limited follow-up information. However, a person's eating behavior changes over time and measurement of consumption at a single point in time does not capture the variability of intake during follow-up, the authors note in the study background.

An Pan, Ph.D., of the National University of Singapore, and colleagues analyzed data from three Harvard group studies and followed up 26,357 men in the Health Professionals Follow-up Study; 48,709 women in the Nurses' Health Study; and 74,077 women in the Nurses' Health Study II. Diets were assessed using food frequency questionnaires.

During more than 1.9 million person-years of follow-up, researchers documented 7,540 incident cases of T2DM.

"Increasing red meat intake during a four-year interval was associated with an elevated risk of T2DM during the subsequent four years in each cohort," according to the study.

The results indicate that compared with a group with no change in red meat intake, increasing red meat intake of more than 0.50 servings per day was associated with a 48 percent elevated risk in the subsequent four-year period. Reducing red meat consumption by more than 0.50 servings per day from baseline to the first four years of follow-up was associated with a 14 percent lower risk during the subsequent entire follow-up.

The authors note the study is observational so causality cannot be inferred.

"Our results confirm the robustness of the association between red meat and T2DM and add further evidence that limiting red meat consumption over time confers benefits for T2DM prevention," the authors conclude.

(JAMA Intern Med. Published online June 17, 2013. doi:10.1001/jamainternmed.2013.6633. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editor's Note: This work was supported by grants from the National Institutes of Health. An author also made a funding disclosure. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Commentary: Oxygen-Carrying Proteins in Meat and Risk of Diabetes Mellitus

In an invited commentary, William J. Evans, Ph.D., of GlaxoSmithKline and Duke University, Durham, N.C., writes: "The article by Pan et al confirms previous observations that the consumption of so-called red meat is associated with an increased risk of type 2 diabetes mellitus (T2DM)."

"Perhaps a better description of the characteristics of the meat consumed with the greatest effect on risk is the saturated fatty acid (SFA) content rather than the amount of oxygen-carrying proteins," Evans continues.

"A recommendation to consume less red meat may help to reduce the epidemic of T2DM. However, the overwhelming preponderance of molecular, cellular, clinical and epidemiological evidence suggests that public health messages should be directed toward the consumption of high-quality protein that is low in total and saturated fat. … These public health recommendations should include cuts of red meat that are also low in fat, along with fish, poultry and low-fat dairy products. It is not the type of protein (or meat) that is the problem: it is the type of fat," Evans concludes.