Ryan Buckman, 26 years old, was previously 22 stone before he decided to create his own diet and exercise regime.
© Rex Features / Jeremy Durkin
The Essex schoolteacher gave up alcohol and stopped going for romantic meals in a bid to shed the weight.
He then celebrated reaching his target by completing a half-marathon, just before he was given the elbow by his girlfriend.
However, Buckman has gone on to better things as he has now landed his dream job as a PE teacher, as well as starting a relationship with fellow teacher Kimberley.
He said: "Looking back I did get obsessed with the calorie counter; I was on it all day and wouldn't eat anymore when I reached the maximum.
"But my ex said she didn't like the attention I got when I lost weight. It pushed us apart and it was sad at the time and I ended up losing too much weight.
"But now after meeting Kim my life feels perfect. She helped me put the calorie counting into perspective and I gained a few pounds to look healthier."
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Buckman had always aspired to be a PE teacher but was too embarrassed of his weight to apply.
He commented: "I'm so proud to be able to help the kids at school who saw me fat and know it's possible to get slim and healthy."
