CLINICAL CONTEXT
According to the current study by LeBlanc and colleagues, some evidence suggests that hydroxyvitamin D (25[OH]D) might be involved in weight regulation, and vitamin D receptors are present on human adipocytes. In weight loss trials, patients with higher 25(OH)D levels experience more weight loss and fat loss than patients with lower levels of the vitamin. Decreased sunlight exposure leads to chronic 25(OH)D insufficiency and subsequent weight gain year round (not just seasonally).
This longitudinal cohort study determines if 25(OH)D levels among 4659 community-dwelling, ambulatory women 65 years and older is associated with weight change at approximately 4 years. This same study then examined a smaller cohort of women (n = 1054) who had 25(OH)D levels measured at 2 separate visits and determined whether change in 25(OH)D levels is associated with change in weight.
STUDY SYNOPSIS AND PERSPECTIVE
It is not quite the cause for celebration dieters dream of, but a study published online June 25 in the Journal of Women's Health provides additional support for the role of vitamin D in weight regulation.
The researchers found that adequate vitamin D levels were associated with less weight gain among women aged 65 years and older during a 4.5-year period, although they failed to find an association for weight loss and vitamin D.
Erin S. LeBlanc, MD, MPH, an epidemiologist and endocrinologist at the Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon, and colleagues tested 25(OH)D status and tracked weight among participants recruited from a long-term Study of Osteoporotic Fractures from 1986 to 1994. The women lived in Baltimore County, Maryland; Minneapolis, Minnesota; Portland, Oregon; and the Monongahela Valley near Pittsburgh, Pennsylvania. They were mostly non-Hispanic white (>99%) and aged 65 years or older.
Using a 25(OH)D level of 30 ng/mL or higher as the marker for adequate vitamin D levels, the investigators found an association between lower weight at baseline and adequate vitamin D levels (141.6 pounds for women with 25 (OH)D levels ≥ 30 ng/mL; 148.6 for women with 25 (OH)D levels < 30 ng/mL; P 99% non-Hispanic white) in 4 US regions. Women unable to walk without assistance and those with bilateral hip replacements were excluded.
All surviving participants were invited to attend a year 6 examination between August 1992 and July 1994.
A total of 6818 women completed the year 6 clinic or home visit, and 6256 had measurement of 25(OH)D levels.
4659 women (74%) had weight measurements at both year 6 and year 10 examinations (average of 4.5 years later); these women were the subject of the baseline 25(OH)D analyses in this study.
A subcohort of women (n = 1054) who participated in the year 10 examination were randomly selected to have 25(OH)D levels retested.
The 1054 women with recorded weight status and 25(OH)D levels at both year 6 and year 10 visits comprised the analytic cohort for the longitudinal 25(OH)D analyses.
The population was divided into women with 25(OH)D levels of less than 30 ng/mL and women with levels of 30 ng/mL or higher.
This cutoff value was chosen because parathyroid hormone levels have been shown to plateau, and calcium absorption has been found to be most efficient at 25(OH)D levels of more than 30 ng/mL.
Participants were categorized based on their weight change between year 6 and year 10 visits.
Those who experienced less than a 5% change in body weight between the 2 visits were considered to have stable weight.
Those who gained 5% or more of their body weight were considered to have gained weight; those who lost 5% or more of their body weight were considered to have lost weight.
Women who had 25(OH)D levels measured were characterized by change in 25(OH)D levels between visits into the following 2 categories: (1) levels remaining at 30 ng/mL or more at both visits or changing from less than 30 to 30 ng/mL or more; and (2) levels remaining at less than 30 ng/mL at both visits or changed from 30 ng/mL or higher to less than 30 ng/mL.
4659 women 65 years and older with baseline 25(OH)D measurement were observed for 4.5 years.
They were weighed at baseline and at follow-up visits; the subset (n = 1054) had 25(OH)D levels measured again at follow-up.
The majority of women (60.2%) were weight stable between year 6 and year 10 visits.
27.5% lost 5% or more of their baseline weight (average loss of 10.4% [15.7 pounds]) between the 2 visits, and 12.3% gained 5% or more of their baseline weight (average gain of 9.7% [13.6 pounds]).
Women who lost weight were older (77 years vs 76 years in weight stable category and 75 years in weight gain category) but did not differ by race and education vs women who were weight stable or gained weight.
Baseline weight and body mass index (BMI) were highest in the weight loss group and lowest in the weight gain group.
Slightly more than one third of women in the weight loss group decreased to a lower BMI category; 40% of those in the weight gain group increased to a higher BMI category.
Among women not trying to lose weight, the number of women with cancer (20%) was the same in the weight stable (21%) and weight gain (20%) groups.
The data suggested that women who lost weight did not have more cancer or other comorbidities.
Women with 25(OH)D levels of 30 ng/mL or higher had lower baseline weight (141.6 pounds) vs women with 25(OH)D levels of less than 30 ng/mL (148.6 pounds; P < .001).
Overall, women with 25(OH)D levels of 30 ng/mL or more had similar changes in weight between visits 6 and 10 (-3.3 pounds) vs women with 25(OH)D levels of less than 30 ng/mL (-2.8 pounds; P = .24).
There was also no difference in 25(OH)D levels or the percentage of women with 25(OH)D levels of 30 ng/mL or higher in the weight loss, weight stable, or weight gain populations.
Overall, 25(OH)D status was not associated with weight change at 4.5 years, but change in 25(OH)D levels was associated with weight change.
In women who gained 5% or more of weight, those with baseline 25(OH)D levels of 30 ng/mL or higher gained 16.4 pounds (12.2% of baseline weight) at 4.5 years vs 18.5 pounds (13.9% of baseline weight) in women with levels of less than 30 ng/mL (P = .04).
In women who lost 5% or more weight or whose weight remained stable (< 5% weight change), there was no association between 25(OH)D status at baseline and weight change.
Among women who gained weight and had 25(OH)D levels measured at both visits, having sustained or developing 25(OH)D levels of 30 ng/mL or higher was associated with less weight gain between visits (14.81 vs 16.34 pounds; P = .04).
The authors concluded that higher 25(OH)D levels were associated with less weight gain in older women, suggesting that low vitamin D status may predispose to fat accumulation.
CLINICAL IMPLICATIONS
Women 65 years and older are likely to remain weight stable at 4 years, with one quarter losing 5% of more of body weight and 12% gaining 5% or more of body weight.
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