All Miss Smale could say was "pardon?", before hanging up the phone.
She then did not get back to them for two weeks before deciding to pull out.
"I think it's important to empower women and know it's OK to be healthy, educated and a good role model," she said. "I didn't hand my crown over straight away.
"I was going to go out of protest, however what example would that be setting?"
Miss Smale was meant to travel to Guayaquil, Ecuador this September before being left hurt by the comments. "I asked her to just tell me exactly what was said," Ms Smale said.
"[I was told] 'she needs to go on a diet plan as she is too big'. "At this point I was so shocked and needed a moment to compose myself."
At the time Miss Smale, who now works in the sports industry, was a size 10.
"I'm not big at all I'm just bang on average," she said. "I just think to be told to lose as much weight as possible for a competition, why would people say that?
"It's horrible and it made me feel so rubbish about myself for a long, long time,' she confessed.."
The Telegraph has contacted Miss United Continents and is awaiting comment.