Janet Jackson doesn't weigh herself.

The ambassador for weight loss plan NutriSystem admitted she opts not to know how much she weighs as a way to stay healthy.

Janet told People: ''I don't know how much weight I've lost, only because I stay away from the scale.''

Speaking at Marco Glavianos Supermodels exhibit in New York recently she said focusing on weight is setting yourself up for failure on diets.

She said: ''I don't think [stepping on the scale] is healthy. You're setting yourself up to fail and women's bodies fluctuate every month - certain time of the month in particular - we bloat a great deal.''

The sibling of the late Michael Jackson turned 46 yesterday (16.05.12) and became the diet company's spokeswoman in December.

She added: ''It works, point blank. You don't have to starve yourself getting there.

''I love Caramel apples! NutriSystem doesn't have that, so that's probably my cheat food. I go out to dinner with friends [too], but then I just get back on it. It's about maintenance.''

However the 'All For You' singer admitted she has to exercise hard to look as good as she does.

She confessed: ''If I'm getting ready for something like a tour, I work out six days a week. I like to switch it up. I may go for a run or bike.

''I'm really happy with the way that I feel at the moment. I feel very good, and it's been a long time since I've felt this good.''