Jessica Alba feels "happier and more productive" when she exercises.
The 'Sin City: A Dame To Kill For' star tries to work out four times a week but admits it is more like two or three times as she is very busy.
She said: "If I work out four times, I consider it a successful week. But it's typically more like two to three days a week because that's what I have time for. I take Spin or hot yoga classes in the morning, and I sacrifice sleep to fit them in.
"For me, the benefits of exercise are more mental than physical. Working out takes away that little edge so that I feel happier and more productive, and my brain can get kick-started."
However, the 35-year-old actress - who has Honor, eight, and Haven, five, with her husband Cash Warren - believes diet is more important than exercise if she wants to lose weight.
She added: "With exercise, I get a little more toned and I definitely feel stronger, but my diet is much more important if I'm trying to slim down. In that case, I usually don't eat gluten, dairy, fried foods or processed foods. I try to stick to a diet that's low in sugar and carbs, and high in lean protein and vegetables.
"I'm not big on carbs, but some of my Honest colleagues and I just ate like a gallon of popcorn! Also, while I don't usually have dessert, I do really like strawberry shortcake. I mean I really, really like it."
Meanwhile, Jessica also admits she loves her body shape and likes to push herself and her body.
She told the October issue of Shape magazine: "I love my shape because it does what I want it to. If I want to go on a hike or a bike ride or go for a swim, I know my body will do everything I tell it to.
"I also appreciate that I can push myself through when I'm feeling tired. There's always a little extra something to get me past the tired moments."
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