Thanks! I can say from personal experience as a guy who waffles around over the years from "good" to "decent" to "excellent" to (occasionally) "superb" shape depending on the energy and attention invested, that it is only in the "excellent" phase and beyond that i truly feel prepared to meet whatever the world has to dish out.

But Foster makes a very good point. In a survival situation it is a very fine line, and if you are truly in crisis, (like lost in the woods and know not what to eat or how to get it) the onus is on you to conserve energy. Look at the ermine: the ermine has very little body mass and a shape that is engineered for losing energy/heat, and yet lives in, among other places, the arctic. How does it survive? By sleeping 9/10ths of the day, and maximizing its hunting during the few waking hours. As soon as it kills and eats, it goes back to sleep in an insulated nest beneath the snow.

This situation is a crisis one for humans. Successful people in my country's history who subsisted in the wilderness (traders, missionaries, mountain men,) got very good at procuring food. The also burned enormous amounts of energy and ate huge quantities of meat. Fortunately for them, there was plenty of wild food to be had. Not to say they didn't know hunger - they did. But overall they were astonishingly vigorous people, whose physical feats were stupefing. (I just finished reading a true one about one guy, who was well into middle age, who snowshoed 70 miles over the Canadian rockies - basically North America's Himalyas) in the depths of winter to keep an xmas dinner date with his family!) Their resting metabolisms would indeed have been very high. These were the sorts of people who forged my country, and they offer a wonderful window into human potential and capabilities under demanding conditions.