(1) For "Fitness for Geeks" you've done quite a bit of research on nutrition, health, physical strength in general and body monitoring. What are your most important (and most surprising) insights in a nutshell?
One insight was the pure breadth and depth of the health/fitness apps; tens of millions of users on EndoMondo, Strava, FitBit, Runtastic, and the like.
You can engineer your own weight loss and fitness gains, as software people are used to an engineering context, using these apps. Track the calories in your diet and your movement level throughout the day (and calories expended) with the FitBit, and connect these data with a Withings body-composition scale, and there you have it, all the data on the same screen, tracked over time so you can look for patterns.
These apps also have a tail-wagging-the-dog effect; they make people exercise more, when everything is being tracked.
I guess another insight that has evolved over the years is that we have been given a lot of "upside down" public-health advice: fats in the diet are bad; the sun is poison, so run around covering yourself with sunscreen all the time; and the more exercise the better (as if lots of marathoning was good for you).
Wrong on all three counts. It's sugar in the modern diet, as in refined sugar and fructose syrup, that's wreaking havoc metabolically (a little bad news there for dessert lovers :), not fat; the sun is healthy for generating the all-important secosteroid hormone vitamin D and for other reasons (some possibly not discovered yet), and "ultra" or excess exercise can damage the heart, suppress the immune system, and lead to some unhealthy outcomes.
"Mother nature does not make bad fats"; man makes bad fats, as in trans fat and rancid vegetable oils, and the like. Eat healthy fat and get control of your fasting blood sugar by eliminating refined sugar, exercising and moving a lot (particularly after eating), as well as fasting.
(2) When was the last time you worked out?
Yesterday I had an interesting workout. We have a 10 kilometer stretch of open beach here north of Boston (Plum Island). It was low tide and the ocean was flat, not too many waves, so I did 6-7 100-meter dashes on the hard sand barefoot, maybe the last few all-out. Then I dived in the water. It was 9-10 degrees C., which I measured with a pool thermometer. Just a quick swim. Very refreshing (and healthy)! Cold-water swimming is a relatively new thing with me; it's remarkable how the body can adapt to it.