As body temperature starts to rise just before awakening in the morning and continues to increase through midday, working memory, alertness and concentration gradually improve. Taking a warm morning shower can jump-start the process.

The correlation between eating and lean-ness is startling:

Is there a best time to eat? To keep from packing on pounds, experts say, limit food consumption to your hours of peak activity. A study in Cell Metabolism last May linked disruptions of the body clock to weight gain. Researchers put two groups of mice on the same high-calorie diet. One group was allowed to eat anytime; the other group was restricted to eating only during an eight-hour period when they were normally awake and active. The mice that ate only while active were 40% leaner and had lower cholesterol and blood sugar.

So... constrain your eating to the window of your highest activity?

Or is it that they're lean because they're not eating 16 hours of the day? :)