How long does it take to lose fitness?

What do you mean by "losing fitness"? That's too vague.

If you mean getting fatter, then if depends entirely on your calories in and calories out. If you eat in a calorie maintenance (eating as many calories as you burn) You'll never get fatter. Be careful, the amount of calories you burn depends on a lot of things such as your amount of physical activity, your metabolism and your age, which affects your metabolism. (the older you are, the slower your metabolism is)

If you mean losing muscle, as far as I know, you can stop doing any physical activity and you can still hold muscle for up to 3 weeks. If you want to preserve muscle and not build more, you can just decrease your effort in the gym to a third of what you kneed to grow muscle. BTW your muscles have muscle memory so even if you do lose muscle, you can regain it much easier.

If you are talking about your cardiovascular health, you can stop doing all physical activity for a week without losing any progress.

What's something you enjoy doing that you never get tired of?

If there is one thing that connects us all together, and makes us different from the other species, is the 'art of conversation'. I can never get tired of conversing and laughing, and conversing a little more.Books are intriguing, but people are fascinating too. To me a conversation is about breaking the wall and

If you had a fast study curriculum for someone who knows nothing about biology to get them to where you think everyone should be, what would it be?

Well, let's say I wanted them to understand some basic paradigms in human tissue engineering, so I can completely ignore almost all non-human biologyHow would I begin the task?First, get them to understand the basic concept behind what a cell is, as well as the Central Dogma as a

Is it possible for me to build muscle while running 12 miles a day?

Yes you can run 12 miles a day and build muscle, I did. When I was training for the Tough Mudder which is a 12 mile long muddy obstacle course the first time, I did P90X for an hour and a half six days a week plus ran a few hours. The second