Marco Borges told Heat magazine: "Beyoncé likes to get in there, get a great workout and get out. She's very driven... there's no complaining. She's the kind of person who's always in search of optimum wellness - she just wants to be healthy."`
He also said that she has been targeting her midriff, doing 200 crunches three times a week.
A source added that the star has never been happier, saying: "She's so thrilled. She's never had abs like the ones she has now and just loves that her stomach is rock-solid. Bey has a healthy diet, but she also loves treats , like wine and Southern soul food.
"But recently she's completely stripped back her diet and got rid of the carbs. She used to eat pasta or Thai curry before a show to give her energy, but now it's all about protein and high-fat foods."