Table 1.

Studies that investigated the connection between obesity and vitamin D.

Ref	Study Design	Study Size	Major Findings
Evans et al. [5]	Cross-sectional case-control study	200	Obesity has a positive impact on peak bone mass acquisition and also obese subjects have greater cortical thickness and cortical tissue mineral density.
Bolland et al. [8]	Cross-sectional study	1984	Vitamin D serum levels show seasonal variations.
Gallagher et al. [9]	Randomized, double-blind placebo controlled study	163	Obese subjects respond with smaller 25(OH)D rise in serum after VD supplementation in comparison to normal weight group.
Drincic et al. [10]	Randomized, single-blind study	67	25(OH)D response after VD supplementation is 30% lower in the obese group. VD supplementation should be adjusted according for body size.
Wamberg et al. [12]	Cross-sectional study	40	Due to different expression of liver enzymes between obese and normal weight groups, adipose tissue can metabolize VD locally which can be altered after weight loss.
Rock et al. [13]	Prospective randomized clinical trial	383	Weight loss increases 25(OH)D serum concentration
Mason et al. [14]	Prospective randomized controlled trial	439	Weight loss of 15% of body weight and above increases 25(OH)D significantly, otherwise weight loss does not impact on serum 25(OH)D
Walsh et al. [19]	Cross-sectional observational study	223	Total and free 25(OH)D and 1,25(OH)2D are lower at higher BMI does not impact bone structure and health.
Macdonald et al. [20]	Prospective observational cohort study	314	Vitamin D deficiency is not related to reduced sun exposure in obese woman. Vitamin D serum concentrations seasonally changes.
LeBlanc et al. [26]	Prospective longitudinal study	9704	Vitamin D deficiency predisposes for obesity, higher doses of VD are related to lower weight gain
Mai et al. [27]	Cross-sectional and prospective cohort study	25,616	Low plasma 25(OH)D level (less than 50 nmol/L) was related to higher BMI and waist circumference.
Zittermann et al. [28]	Randomized, double-blind placebo-controlled study	200	VD supplementation has positive impact on several cardiovascular disease risk markers in obese, but does not adversely affect weight loss
Wamberg et al. [29]	Randomized, double-blind placebo-controlled study	52	VD supplementation has no effect on obesity-related complication nor on body weight reduction.
Kampmann et al. [30]	Randomized, double-blind placebo-controlled study	16	VD supplementation does not improve insulin resistance, blood pressure, inflammation or HbA1c, but might increase insulin secretion.
Mason et al. [31]	Randomized, double-blind placebo-controlled study	218	VD supplementation does not reduce body weight.
Wamberg et al. [36]	Randomized, double-blind placebo-controlled study	40	Inflammatory cytokines and inflammatory markers expression in adipose tissue were not reduced after VD supplementation, nevertheless it had significant inflammatory effects in AT in vitro.
Schleithoff et al. [38]	Randomized, double-blind placebo-controlled study	123	Improvement of VD status decreased plasma proinflammatory cytokines in patients with congestive heart failure.
Pittas et al. [39]	Randomized, double-blind placebo-controlled study	314	VD and calcium supplementation did not affect circulating levels of cytokines but attenuate increases in glycemia and insulin resistance in nondiabetic subjects.
Baynes et al. [42]	Prospective population-based cross-sectional study	142	VD hypovitaminosis is associated to hyperglycemia.
van Hurst et al. [44]	Randomized, double-blind placebo-controlled study	81	VD supplementation improves insulin sensitivity, but has no effect on insulin secretion.
Drincic et al. [47]	Cross-sectional study	686	Body weight and VD plasma levels are conversely associated due to volumetric dilution.

Vitamin D (VD).