Rising serum 25-hydroxy-vitamin D levels after weight loss in obese women correlate with improvement in insulin resistance.
OBJECTIVE
The objective of the study was to examine changes of 25-hydroxy-vitamin D (25OHD) and PTH blood levels 4 and 20 wk after low-calorie diet-induced weight loss.


METHODS
Forty-four obese women [aged 40.6 +/- 11.4 yr, body mass index (BMI) 36.7 +/- 4.9 kg/m(2)] and 25 controls (BMI 22.9 +/- 1.5 kg/m(2)) were examined. Anthropometric and cardiometabolic parameters and 25OHD and PTH levels were determined at baseline and 4 and 20 wk after a low-calorie diet.


RESULTS
At baseline, 25OHD levels were lower in obese compared with control subjects (17 +/- 6.0 vs. 23.8 +/- 8.7 ng/ml, P < 0.001), whereas no differences were found in PTH levels. In all women, a negative correlation was found between 25OHD levels and body weight (BW) (r -0.32, P < 0.001), BMI (r -0.37, P < 0.001), waist circumference (r -0.26, P < 0.05), and percent fat mass (r -0.38, P = 0.001) as determined by bioelectrical impedance analysis. The 4-wk low-calorie diet (n = 37) reduced BW and led to significant improvements in the homeostasis model assessment (HOMA) index and lipid levels. The 20-wk low-calorie diet (n = 26) resulted in reduction of BW and BMI by 10%, HOMA index (4.7 +/- 3.8 vs. 3.10 +/- 1.7, P < 0.01), and lipids levels (except high density lipoprotein cholesterol) and increase in 25OHD (15.4 +/- 6.0 vs. 18.3 +/- 5.1 ng/ml, P < 0.05), compared with baseline. PTH levels were unchanged. The increase of 25OHD levels was associated with the reduction of insulin levels and HOMA index (r -0.43, P < 0.05).


CONCLUSIONS
Blood 25OHD levels were low in obese women and correlated inversely with severity measures of obesity. Weight loss of 10% after low-calorie diet increased 25OHD levels, and this increase was mainly associated with improvement of insulin resistance.
Department of Endocrinology, Diabetes, and Metabolism, Panagia General Hospital, 55132 Thessaloniki, Greece.
Themistoklis
T
Tzotzas
Fotini G
FG
Papadopoulou
Kostantinos
K
Tziomalos
Spiros
S
Karras
Kostantinos
K
Gastaris
Petros
P
Perros
Gerasimos E
GE
Krassas
D000328:Adult; D031204:Caloric Restriction; D008076:Cholesterol, HDL / Q000097:blood; D004038:Diet, Reducing; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000178:diet therapy / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000097:blood; D015854:Up-Regulation; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D015431:Weight Loss / Q000502:physiology*
D008076:Cholesterol, HDL; D007328:Insulin; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D