Outlook: Obesity

Obesity in Middle Age Linked to Dementia

Individuals who are overweight or obese during middle age may be at an increased risk for developing certain dementias, according to research published in the May 2011 issue of Neurology.

In the study, Weili Xu, MD, PhD, of the Karolinska Institutet in Stockholm, Sweden, and colleagues analyzed data from the Swedish Twin Registry on 8534 twins 65 years or older. Of the participants, 2541 had been classified as either overweight or obese between age 40 and 60; 350 of these overweight individuals eventually developed dementia, and 114 had possible dementia. Only 3% of healthy seniors had been obese during middle age.

The study found that people who were overweight or obese at midlife had an 80% higher risk of developing dementia, Alzheimer’s disease, or vascular dementia in late life compared with people with normal body mass index. The results remained the same after considering other factors, such as education, diabetes, and vascular disease. A total of 26% of those with no dementia had been overweight in midlife, compared with 36% of those with questionable dementia and 39% of those with diagnosed dementia.

“Our results contribute to the growing evidence that controlling body weight or losing weight in middle age could reduce your risk of dementia,” said Dr. Xu.

Greater Weight Loss Equals Increased Vitamin D Levels

Findings from a study published in the May 2011 issue of the American Journal of Clinical Nutrition indicate that overweight or obese women with low levels of vitamin D who lose more than 15% of their body weight experience significant increases in circulating levels of the fat-soluble nutrient.

“Since vitamin D is generally lower in persons with obesity, it is possible that low vitamin D could account, in part, for the link between obesity and diseases such as cancer, heart disease, and diabetes,” said Caitlin Mason, PhD, of Fred Hutchinson Cancer Research Center, lead author of the paper. “Determining whether weight loss helps change vitamin D status is important for understanding potential avenues for disease prevention.”

The study included 439 overweight-to-obese, sedentary, postmenopausal women aged 50 to 75 years, who were randomly assigned to 1 of 4 groups: exercise only, diet only, exercise plus diet, and no intervention. Those who lost 5% to 10% of their body weight through diet and/or exercise saw a relatively small increase in blood levels of vitamin D (about 2.7 ng/mL), whereas women who lost more than 15% of their weight experienced a nearly 3-fold increase in vitamin D (about 7.7 ng/mL), independent of dietary intake of the nutrient.

“It appears that the relationship between weight loss and blood vitamin D is not linear but goes up dramatically with more weight loss,” said senior author Anne McTiernan, MD, PhD, principal investigator of the study.

“While weight loss of 5% to 10% is generally recommended to improve risk factors such as blood pressure, cholesterol, and blood sugars, our findings suggest that more weight loss might be necessary to meaningfully raise blood vitamin D levels,” said Dr. McTiernan.

Sedentary Employment Contributes to Obesity

The growing number of jobs that require little physical activity has contributed significantly to the rapid increase in obesity rates, according to a study published in the journal PLoS One in May.

Factors such as automation and different working systems have transformed a number of physically active occupations into predominantly sedentary ones, researchers found, noting that approximately 20% of private industry jobs in the United States today require a moderate level of physical effort, compared with 50% 5 decades ago.

“Over the last 50 years, we estimate that daily occupation-related energy expenditure has decreased by more than 100 calories, and this reduction in energy expenditure accounts for a significant portion of the increase in mean US body weights for women and men,” the authors wrote.

In the study, a team of researchers led by Timothy S. Church, MD, MPH, PhD, of Louisiana State University, gathered data from National Health and Nutrition Examination Surveys and the Bureau of Labor Statistics, which included details on workers’ body weight and estimated energy expenditure requirements. The researchers calculated that the average American worker today requires at least 100 fewer calories to do their job each day than in the early 1960s, which can translate to 4.4 extra pounds of fat over a period of 180 working days.

The authors emphasized that there are other factors contributing to the current obesity epidemic, including lack of physical activity. “Given that it is unlikely that there will be a return to occupations that demand moderate levels of physical activity, our findings provide further strong evidence of the public health importance of promoting physically active lifestyles outside of the work day,” they wrote. PT