People that are really fit, or recently fit, seem most prone to bonking and so they really need to do their research to understand what they are doing. Dr. Tim Noakes, the Lore of Running, is a good read. Midnight Sun's posts on health and nutrition are always good to read, often tieing in sunstroke, heat stroke, hypothermia, with dehydration and glycogen depletion, and the additional risks of accidents or poor judgement.

A somewhat unique category I find myself in now, and others may, is when I combine hiking with weight loss. Just as the more atheletic outdoor enthusiasts needs to be more careful when pushing themselves harder, the dieting hiker needs to do likewise. Some days and surroundings and circumstances are safer than others to lose more weight, just as some days are safer than others for pushing yourself to your cardiovascular and energy limits. You can get into great shape, and lose a heck of alot of weight if needed, without taking undue risks, but you need to do some research and exercise some vigilance in order to be aware of the risks that you may unknowingingly be putting yourself through, when you push a little harder, or back off a little too much on the food consumption. Err on the side of caution, especially when going solo, or if the weather or topographical or other physical challenges are more extreme. Moderation is key. If an activity doesn't include some element of boredom, its probably too extreme.

Nice scenery helps, and bring a friend along if you can.