Jessica Biel had a "bad attitude" when she was growing up.

The American actress knows she probably made things hard for her family when she was younger because she wasn't much fun to be around.

Girls teased her at school and it had an impact on how she behaved.

"As a teenager, I had a bad attitude due to my insecurities. I was trying to create a defensive persona when I was 16. I was confident but insecure, pushing the envelope but still being a kid and thinking I was this strong, independent woman when I still wasn't there yet," she admitted.

The star took part in Pilates contests in the US when she was a teenager. Developing a love for the low-impact form of exercise is what helped get her through the hard times.

"When I did Pilates competitions, I started to work on my appearance and body and was determined to make some of the nasty girls who tortured me feel jealous," she laughed to British magazine Look.