Mr Watson, whose weight loss over the past year has been well documented, said he was scared of dying early and began exercising and stopped eating processed food.
And he used his story to announce his party’s commitment to halt the “public health crisis” of 3.5 million people suffering Type 2 diabetes.
Writing in the Daily Express on Wednesday, the 51-year-old said: “It was last summer, as I huffed and puffed the 76 steps to my Westminster office, that I realised the damage I had done to my body and my health.
“Overweight, deeply unfit, addicted to sugar and fast foods, it was little surprise when the doctor told me I had Type 2 diabetes.
“I recalled overweight Labour politicians dying early in their 50s and 60s and thought about whether I was actually going to see my two children grow into adults, or their children grow up.
“I vowed to change my lifestyle and began reading up about nutrition, exercise and diabetes.”
He continued: “I don’t just feel healthier but stronger, happier and mentally far more agile.
“Today I am very happy to reveal that my Type 2 diabetes has been reversed, it’s in remission.
“No longer having to take medicines for diabetes is a joy.
“To all Type 2 diabetics I say: ‘Yes, we can.’ Yet the tragedy for many Type 2 diabetics is that they don’t even know their condition is reversible, let alone how to achieve it.”
Type 2 diabetes causes the level of sugar in the blood to become too high. The NHS said it can cause symptoms like excessive thirst, needing to urinate regularly and tiredness.