One of the easiest ways to burn extra calories is to walk 2-3 miles every day. A lot of people think that this is nonsense because walking is such an easy activity. Well... it isn't. At least not when you are carrying a backpack with an extra 20-70lbs.
You see, carrying so much extra weight instantly makes you burn A LOT more calories simply because your body has to work that much harder to move from place A to place B (for all you geeks out there think dragon ball z and the gravity capsule).
Walking with a weighted back pack allows you to preserve lower body muscle mass. It also increases you fitness level, your core strength AND it doesn't hurt your knees as much as running.
|30lbs and a backpack|
You can use whatever you want to add weight to your backpack just make sure that a) you have a QUALITY backpack and b) don't try to carry enormous amounts of weight on your first day.
Walk 2-3 miles with your backpack everyday for a week and you'll see how great it is.