The 29-year-old singer is believed to have turned her back on fatty fast food in favour of fruit, wholemeal toast, sushi and lots of chicken or fish.
“She’s also downing at least three litres of water per day, which accounts for her clear complexion,” a source told Now magazine.
“If Britney craves a burger or the Southern food she loves, she just refocuses.
“She’s in such a good place emotionally that it’s easier to keep up her strict diet.
“She’s back to dancing six days a week, living and breathing the tough regime of a full-time dancer. She’s feeling as good as she looks right now.”