Posh Spice has been told that she will have to increase her food intake if she wanted to keep up with the strenuous dance routines planned for the tour.
Known for her thin frame, Beckham maintains a waist measuring 23in by eating steamed fish and edamame (soybeans).
But now a source has revealed those as a part of the new diet the singer would have to, firstly, detox her body system and later would be eating brown rice with steamed vegetable.
"First Victoria is going on a weeklong cleanse where she will only be able to drink hot lemon water and eat organic fruit and vegetables to detox her system," the Daily Mail quoted the source, as saying.
"She will have to keep this up for five days even though she will be training. Her new diet is based on eating small bowls of brown rice with steamed vegetables.
"Her favourite at the moment is steamed spinach, carrots and tomatoes. She will also be eating beetroot at every mealtime because it's a good source of fibre and iron and low in calories," the source added.
Posh would also have to eat handfuls of nuts and seeds as four or five small meals a day.
"She is terrified of putting on a single pound and has had to be talked into increasing her food intake.
"It would be very embarrassing for her if she collapses or gets ill because she's too weak," the source said.