When we eat carbohydrates they are broken down in our digestive system and absorbed into the blood, where they are either used as energy or stored as fat. By not all carbohydrates are absorbed at the same rate. Simple forms of carbohydrates (sugars) are quickly broken down and used, where starches are, or more complex carbohydrates require more work to be broken down and used as energy, and fibre, both soluble and insoluble, can’t be used for energy at all.
Insulin is a hormone released by the pancreas (a gland/organ) which regulates how much sugar is in the blood. Too much blood sugar is toxic to the body. Insulin makes our muscle, liver and fat cells take up blood sugar and covert it to glycogen or triglycerides for storage. Muscles store glucose as glycogen which is used to fuel muscles, fat stores glucose as triglycerides. The liver also processes carbohydrates and stores them for use when necessary. So you can see that if you eat more energy than your body requires for your muscles, fat cells are more than happy to take on the excess (so is your butt).
A slowly absorbed source of carbs gives our body’s more chance to use the energy than store it, whereas sugars, unless you exercising very soon, and at a high intensity, are more like to be stored- especially if you’re sitting on your backside while eating them. Carbs are you body’s preferred source of energy- we are set up to use them very efficiently. Although these days the need to spontaneously run away from a Sabor Tooth Tiger is not great (largely because they are extinct-but that’s a minor detail) so perhaps, unless exercising frequently, our needs for carbohydrates to fuel us has changed since we were first put together. Huge spikes in blood sugar levels generally come with a corresponding blood sugar low, which helps explain the slump in energy after you eat a really carbohydrate rich meal. The goal is to keep blood sugar levels as stable as possible and avoid the constant release of insulin to get rid of the excess sugar. Low GI carbohydrates- the slow burning ones- are best suited for when you are less active, and the faster burning carbs are useful around training and times. And then there ware those lucky humans who just seem to be able to eat until the cows come home and probably lose weight… I’m happy for you...*teeth clenched*.
So basically it’s not carbs per se that need to be feared like they currently are- it’s the TYPE and TIMING of the carbs which means the difference between an energetic, well fuelled gym goer and being sluggish and unhappy with your weight.