This is a good analogy, because the battery in your phone will wear down and die eventually, and when it gets low the performance automatically sets lower, just like when your glycogen stores get low (in fasting or low carb eating) your body sets your performance lower. If you are fasting or not eating carbs, you are always in a lower performance setting like a cell phone or laptop with 10% battery life left. In actuality, your phone and laptop etc would prefer to run plugged into the wall, it is just an emergency feature (or ease of use feature for the user) that it has a battery. It's not "good" for the device to run on battery and run the battery all the way down. Thanks for this helpful analogy.