How and where your carbs are stored is key to knowing what to eat

Carbs are stored as either fat or glycogen (stored sugar). The key is that there are two types of glycogen that go in two very different-sized "storage bins" in the body, each with a different primary purpose:

Storage Bin 1: The liver - holds about 100 grams of carbs which are used to keep general circulating blood sugar up to the brain and muscles during the day

Storage Bin 2: The skeletal muscles - hold about 200-600 grams of carbs depending on how much muscle you have; these carbs are used primarily for the muscles themselves, but can be "dumped" into the bloodstream when the liver runs out if necessary. It is key that there is a very wide variation in how easily people "let go" of the sugar in their muscles, which is reflected in how easily some people hold on to muscle mass while others lose it fast.

Secondly, it is key that the fructose you eat (from fruit and sweets) can only be stored in the liver--remembering that liver stores are relatively small. Therefore you can easily go over your storage capacity when you eat too much fructose, and the excess automatically turns to fat. The point: fructose is easy to overeat. Little bits throughout the day are better than gobs all at once.

Thirdly, those trying to build muscle mass will get no use out of fructose in terms of replacing the sugar in their muscles after working out, as fructose will never end up in muscles. Instead, they need to eat starches like root vegetables, beans, potatoes, and grains (though grains have many downsides). Again, these cannot be eaten all at once, better in small bits throughout the day so as to avoid jacking blood sugar up, which spikes insulin and leads to more carbs stored as fat.

Finally, always eat some protein with carbs to keep your blood sugar from dropping through glucagon.