Kate Upton feels most confident when she has "good make-up on".
The Sports Illustrated model admits she feels "powerful" when she's had her make-up done and has brushed her hair but insists confidence must come from within.
She said: "When I first started modelling, it was hard on my hair because of all the hot irons used on it. Then I learned about a brand called Leonor Greyl, and since then I use its shampoo and hair mask as a conditioner every time I wash my hair. When I'm confident, I feel powerful, and I feel confident when I have good make-up on and my hair is brushed.
"Confidence is being yourself. Women often get competitive with each other, when we should really be competitive with ourselves. It's more about improving yourself and becoming the best person you can possibly be."
The 23-year-old beauty also revealed she works out three times a week and aims to eat "clean" as much as possible.
She added to The Telegraph's Stella magazine: "In order to stay fit and healthy, I work out three times a week and I try to eat clean. It helps me have energy after long days and lots of travelling.
"I'm lucky because I actually like the food I eat. I love fish or chicken, grilled vegetables, sautéed spinach with feta cheese, and a good juice. David Kirsch's Super Charged Greens Blend is my post-workout drink."