Whether it’s at your desk or on a couch, sitting for hours on end is bad for your health. It’s linked with obesity, heart disease, and high cholesterol. When you sit for too long, an enzyme that turns harmful LDL cholesterol into good HDL cholesterol drops by 95%. To protect your heart, take frequent breaks. Stand up at least every 30 minutes and, if you can, go for a 5-minute walk every hour.