Obesity and Circulating Levels of Vitamin D before and after Weight Loss Induced by a Very Low-Calorie Ketogenic Diet

Abstract

Background: Vitamin D plays a pivotal role in calcium and phosphorus metabolism, also influencing bone tissue. Several studies have reported that vitamin D blood levels were significantly lower in people with obesity, probably due to its uptake by the adipose tissue. Clinical studies that investigated the changes of circulating levels of vitamin D following weight loss reported controversial data. A very low-calorie ketogenic diet is acknowledged as a reliable treatment to achieve a rapid weight loss. Therefore, we investigated the effect of weight loss, consequent to a very low-calorie ketogenic diet, on vitamin D blood concentrations. Methods: A cohort of 31 people with obesity underwent a very low-calorie ketogenic diet for 10–12 weeks. The serum concentrations of vitamin D, parathormone, calcium and phosphorous were measured before and after weight loss; they were compared to a control group of 20 non-obese, non-diabetic, age- and gender-matched persons. Results: Patients with obesity had a higher habitual intake of vitamin D than the control group (p < 0.05). However, the vitamin D blood levels of the obese group were significantly lower than those of the control group (p < 0.005) and they increased after weight loss (p < 0.001). At baseline, vitamin D blood concentrations of the persons with obesity were significantly correlated with both fat mass–kg (r = −0.40; p < 0.05) and body mass index (r = −0.47; p < 0.01). Following very low-calorie ketogenic diet, the change in vitamin D serum concentrations was correlated only with the change in fat mass–kg (r = −0.43; p < 0.01). Conclusion: This study confirmed that patients with obesity have lower vitamin D levels that normalize after significant weight loss, supporting the hypothesis that vitamin D is stored in the adipose tissue and released following weight loss.

Ketogenic Diet as Medical Prescription in Women with Polycystic Ovary Syndrome (PCOS)

“…In their study, they evaluated the change in vitamin D concentrations in 31 subjects with obesity before and after dietary treatment with VLCKD. Subjects with obesity had lower vitamin D levels, and at the end of the 10-12 weeks dietary intervention, the increase in vitamin D levels correlated with the reduction in body weight and especially fat mass [44]. Thus, this study supports the hypothesis that vitamin D is stored in adipose tissue and released after weight loss.…”

“…Hence, weight loss and decreased fat mass might restore regular vitamin D levels and insulin sensitivity. As reported by Buscemi et al, vitamin D blood levels were significantly lower in subjects with obesity, probably due to its uptake by the adipose tissue [44]. In their study, they evaluated the change in vitamin D concentrations in 31 subjects with obesity before and after dietary treatment with VLCKD.…”

25-hydroxyvitamin D levels are inversely related to metabolic syndrome risk profile in northern Chinese subjects without vitamin D supplementation

“…One possible explanation is that the stored 25(OH)D in adipose tissue, especially in visceral fat, was being released following the fat mass reduction. In agreement with our result, Buscemi S, et al also found that significant decrease in BMI, WC and fat mass (FM) induced by a very low-calorie ketogenic diet resulted in the increased serum 25(OH)D levels [ 40 ]. A meta-analysis which recruited 18 clinical trials also demonstrated that serum vitamin D levels were increased with weight and FM loss [ 41 ], further supporting the hypothesis that increases in serum 25(OH)D levels would be a result from direct mobilization of stores into the circulation upon decrease of FM in the obese subjects.…”

Correlation of Obesity and Serum Vitamin D Levels with Sperm DNA Integrity, Sperm Quality, and Sperm Viability in Normozoospermia Men

“…Obesity showed lower concentrations of VD levels, which normalized after weight loss. [ 21 ] This may be due to less exposure of obese men to ultraviolet radiation, which stimulates biosynthesis of cholecalciferol (VD3) from cholesterol. [ 22 ] Indeed, the synthesis of an active metabolite of VD known as 1,25-dihydroxy VD is enhanced, and high levels showed negative feedback impact on synthesis of 25-OH VD in the liver.…”