After consuming very low carb for days and then burning 1000+ calories in a single 11 mile run... my body will find the carbs needed to power my muscles from sources other than my diet. Basically it will burn
fat.
The key thing for me is that if I *do* consume a lot of carbs in my diet, my body will-not-burn-as-much-fat and at a certain point will start packing-fat-on.
In the past 7 days I have consumed 9,806 calories (1,400 a day) yet I am up 3 net pounds (170lbs > 173lbs). During this time I had a *calorie deficit*. I run 3 miles a day on average and walk 15k-20k steps. There is no way I don't burn more than 1400 calories a day.
The only explanation is that in the past 7 days I have consumed 569 carbs (81 carbs a day). Last month my carb average was 43 carbs a day.
For me, I 'pay a price' when I consume high carbs...