Hi there, thank you for writing. I agree with you that this is a very large amount of weight to be gaining and losing every year. I would want a little bit more information, like how long this cycle has been continuing for, and if you have any other symptoms associated with it, and what times of year you tend to gain and when you tend to lose. My recommendation at this time would be to arrange a visit with your primary care doctor with this additional information and to perhaps consider an endocrinological workup for these problems. (Imbalances in your thyroid hormone production, for example, can cause weight gain or loss). I hope my answer has been helpful to you. Best of luck!