RETN and Insulin resistance: A case–control study in Thailand (26) found a negative association between BMI, waist, and hip circumference and serum concentrations of vitamin E and retinol, and another study (27) showed a significant association between vitamin A and insulin resistance in morbidly obese patients which may be due to the fact that high doses of vitamin A may inhibit the formation of mature adipocytes and also indirectly modifies insulin sensitivity by regulating the production of bioactive proteins secreted by adipocytes, including leptin and resistin.