Kate Beckinsale follows a diet based on regular blood tests.
Kate Beckinsale
The 46-year-old actress consults with nutritionist Dr. Goglia - who creates food programmes based on the samples - and her personal trainer, Brad Siskind, also finds the results useful in his work.
He told OK! magazine: "Without blood work, you're essentially throwing darts at the board with your eyes closed.
"Blood work reveals all truths and then we can create a workout programme to achieve a certain look the client wants."
The 'Underworld' star has worked with Brad for two years, and he revealed she always pushes herself hard during their sessions together.
He said: "Kate works her tail off in the gym. She's focused when she's training and shows up ready to work.
"We've got a great rhythm and the hour just flies by. She makes my job very easy."
The pair train for an hour a day, six days a week, and they have a very specific schedule to stick to.
Brad explained: "We do whole body training, otherwise known as peripheral heart action, which involves training the upper then lower body, so that the blood is continually moving all over the body.
"This kind of training burns the most calories because we are using the entire body.
"It involves eight to 10 exercises, then we finish the round with a quick two-minute cardio interval, which we repeat. Finally we stretch."
The 'Farming' actress previously revealed she takes her own packed lunch to set with her because she has a lot of allergies.
She said: "I'm incredibly self-sufficient and I always bring my own food. I'm allergic to enough things that it's pointless for me to try the curry.
"I have to just make sure I have protein every few hours or I'll keel over."
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