It takes at least 45 minutes and 30 minutes to start burning fat ~ Sit-ups can keep fit, but they don't lose weight ~ Besides jogging, you can also walk fast and do aerobics ~ I downloaded one from the Internet for 50 minutes every day, but it's still relatively easy to stick to it ~ I also downloaded a mint light card. It's still effective to lose weight and monitor your daily calorie intake ~ It's important to stick to it ~