Before I join HealthUnlocked I have to ask: Is it possible to lose weight with an Underactive Thyroid. I have tried to lose weight though exercise, and it hasn't worked. My doctor once told me that cutting down on my eating will not help me lose weight. I now know this to be true. But I would like to know if HealthUnlocked have the answer for the many sufferers of an Underactive Thyroid, on how to lose weight. I was in my late fifties when first diagnosed and am now 74.