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Vitamin D, BMI and RYGB

Vitamin concentrations and BMI variation after RYGB

Study evaluated 25(OH)D deficiency and body composition of female patients who had RYGB and relate the variation of BMI after surgery to 25(OH)D concentrations
The authors verified that 25(OH)D deficiency was more frequent in the RYGB group, even after adjusting for ethnicity, smoking, BMI, and vitamin supplementation

Women who had Roux-en-Y Gastric Bypass (RYGB) had higher BMI and vitamin D deficiency, along with hyperparathyroidism after three years, compared to a non-surgical control group, according to researchers from Brazil. The study authors found no association between variables related to body composition and 25(OH)D concentrations, although vitamin concentrations correlated negatively to BMI variation after undergoing surgery.

The paper, ‘Is There Association between Vitamin D Concentrations and Body Mass Index Variation in Women Submitted to Y-Roux Surgery?’, was published in the Journal of Obesity by researchers from the Faculdade de Medicina do ABC and Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, SP, Brazil.

The researchers wanted to examine the behaviour of biomarkers associated with vitamin D deficiency in relation to body composition of obese women who have undergone bariatric surgery, and therefore designed a study that evaluated 25(OH)D deficiency and body composition of female patients who had RYGB and relate the variation of BMI after surgery to 25(OH)D concentrations.

They evaluated 49 adult female volunteers who had RYGB 3.3±1.1 years before and 41 healthy non-obese volunteers (control group) with similar age and socioeconomic condition to those of the study group. The women who had undergone RYGB and the control group were submitted to anthropometric evaluation using an analogue scale to classify the nutritional state based on the BMI.

Outcomes

In the group of women submitted to RYGB, the average age was 45.0 ± 9.0 years (minimum and maximum: 23 to 63 years), the average weight loss was 46.9±16.4kg and BMI reduction 30.7±4.7.

The RYGB group, compared to the control group, had more Caucasian women (35 (71.4%) vs. 16 (39.0%); p<0.001), more frequent use of supplements containing vitamin D (33 (67.3%) vs. 1 (2.4%); p<0.001), and lower percentage of smoking (3 (6.1%) vs. 12 (29.3%); p=0.004).

The average 25(OH)D concentrations in the RYGB and control groups were 22.7±11.8ng/ml and 28.9±8.9ng/ml (p=0.008), respectively. 25(OH)D values compatible with deficiency (<20 ng/ml) were observed in 27 (55.1%) and eight (21.1%) in the RYGB and control groups (p=0.002), respectively. Secondary hyperparathyroidism was more frequent in the RYGB group, compared to the control group (15 (30.6%) versus (2.6%); p=0.001) After binary logistic regression, the authors verified that 25(OH)D deficiency was more frequent in the RYGB group, even after adjusting for ethnicity, smoking, BMI, and vitamin supplementation.

The authors reported no association between variables related to body composition and 25(OH)D concentrations, although 25(OH)D concentrations correlated negatively (p=0.001) with BMI variation after the RYGB, i.e. 25(OH)D concentrations were lower in individuals with higher BMI variation, regardless of vitamin D supplementation (Figure 1).

Figure 1: Association between vitamin D concentrations and BMI variation in the group submitted to RYGB with and without supplementation. The Pearson correlation between 25(OH)D and BMI variation (p=0.001).

The study showed that vitamin D deficiency was more frequent in the RYGB group, even after adjusting for variables such as ethnicity, smoking, BMI, and vitamin supplementation. This deficiency in post-bariatric surgery patients, the authors noted, has been related to several factors some of them are associated with excess adiposity and others with the type of surgical procedure.

“Women submitted to bariatric surgery (RYGB) around three years ago presented higher BMI and vitamin D deficiency, along with hyperparathyroidism, compared to the control group. There was no association between variables related to body composition and 25(OH)D concentrations,” the authors concluded. “On the other hand, vitamin concentrations correlated negatively to BMI variation after undergoing surgery. Future studies evaluating the impact of supplementation on biomarkers associated with vitamin D deficiency and taking into account the length of the alimentary and biliopancreatic limbs are necessary.”

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