maria twomey , 42 , of watford , decided hit 40 and decided it was time for a change .
wanted to slim from size 14 and signed up for personal training sessions .
swapped takeaways and fatty snacks for weight-lifting and hiit workouts .
in a year she went from 12st 7 lb to her slimmest , 8st 7 lb .
she 's reduced her body fat percentage from 38 per cent to 15 per cent .
now taking part in miami pro world championships fitness model comp .