Despite copious hype about "afterburn," scientists have debunked the notion that exercise sparks a rise in your metabolism that lasts for hours after a workout. Still, backpacking likely raises your basal metabolism, because the extra muscle you build hauling your pack boosts your fuel needs even when at rest. Muscles drink fuel at SUV rates, while other tissues burn energy like compact cars. Add some quad muscle, and your body suddenly needs more fuel just to maintain your physique. And studies have shown that backpacking at altitude cranks up your metabolism, says Dr. Braun.