ASince I turned 40 it has been a constant battle with my weight...I have gained 30 lbs since turning 40. I diet and exercise and my weight up and down by 5 to 10 lbs. It is a constant battle. I recently saw my doctor and the only explanation other than my age was that I have low vit D levels. I am now taking vit D daily (3000iu's) and fingers are crossed that it helps. He also told me that vit D deficiency causes fatigue and I have been exhausted for the past couple of yrs. Has anyone taken vit D and seen any difference in weight or energy?