The 'LA Love' hitmaker, who has two-year-old son Axl with husband Josh Duhamel, regularly sees a trained therapist and believes it helps her stick to a healthy diet.
She told America's OK! magazine: "It works! I get into a very relaxed state, where she can speak to my subconscious. It's almost a dream state, so you're highly suggestible. I've done hypnosis for eating, and later I'll got to the refrigerator and hear her voice telling me to be sensible."
The 39-year-old singer always makes time to work out, but only recently found time to record a follow-up to her debut album, The Dutchess,' which was released eight years ago.
Asked why it took her so long, she explained: "Between workout time, husband time and mommy time, there's a lot going on. But every time I get an idea, I write it down or record it, so I finally got to finish all those ideas.
"After 'The Dutchess' and two Black Eyed Peas albums, I said, 'Guys, we've got to take a break.' I got pregnant, started renovating our house - genius, I had to move into a renal property while pregnant, moved back into the house, which still isn't done, by the way, and then started figuring out to be a mom."
See the gallery below for images about amazing weight-loss transformations.