I'll add one more anecdote for IF. I've been doing it for 3 years and for me it's been the most effective way to get in and stay in shape. Coffee with a bit of milk or cream in the morning keeps me until 1-3pm (I've never gone full bulletproof coffee, but coffee definitely helps.) As others have mentioned, a run feels really good toward the end of the fast.

Heavy olympic lifting hasn't been a problem but I only lift on high calorie days, and not more than 4 times a week. If you are into the Leangains flavor of IF, lifting is the recommended way to do IF. I find that in my and my gfs case, lifting has been far more effective than cardio.

I grew up with a mother as an aerobics instructor and I live in a very active Seattle, so I've seen and tried all number of diets and workout regimens. With IF I have the most energy and the fastest results. It's also reasonably easy to work into real life situations (travel, dinners at friends' houses, etc.).

I will say that using a calorie and exercise counter is very very helpful when starting or resuming IF. Otherwise it is far too easy to mis-estimate calories in or out. I use Fatsecret app. And to calculate target calorie in/out, there is a great tool here at 1percentedge [1]. (Unfortunately it's in Flash, contacting the author to port to a mobile app is on my long list...)

[1]: http://www.1percentedge.com/ifcalc/