Going for three, 15-minute brisk walks a day is enough to burn up 250 calories without breaking a major sweat. A brief power walk to pick up your morning latte, during your lunch break and after dinner is a great way to boost your calorie burn, and if you tread outdoors, it may even help to boost your mood too. One 2011 study published in the journal Environmental Science and Technology found that people who exercised outdoors reported increased energy and decreased feelings of depression, so get some fresh air and go an extra mile – your body will thank you.