Here are the links I promised:
Joe Rogan:
study on vitamin D makes reference to dark skin:
People with a naturally dark skin tone have natural sun protection and require at least three to five times longer exposure to make the same amount of vitamin D as a person with a white skin tone.[37,38] There is an inverse association of serum 25(OH)D and body mass index (BMI) greater than 30 kg/m2, and thus, obesity is associated with VDD.[39]
study on obesity and vitamin D :
Recent findings: Vitamin D is fat soluble, and distributed into fat, muscle, liver, and serum. All of these compartments are increased in volume in obesity, so the lower vitamin D likely reflects a volumetric dilution effect and whole body stores of vitamin D may be adequate. Despite lower serum vitamin D, obese adults do not have higher bone turnover or lower bone mineral density. Patients undergoing bariatric surgery do have bone loss, and ensuring vitamin D sufficiency in these patients may help to attenuate bone loss.
