We eat from 3 main food groups - carbohydrates, fats, and proteins. Our body needs all three of the food groups to survive and thrive. Carbohydrates which are often referred to as carbs, come in two varieties: sugars and starches. Sugars are simple carbs usually sweet tasting like sweets, doughnuts, candy, etc. and are easily digested. Whereas, starches are complex carbs found in bread, pasta, noodles and rice and take longer to digest, with stomach acids breaking them down. The body transforms all these digestible carbs into glucose, the sugar that our cells use as fuel or energy. When glucose molecules pass from the intestine into the bloodstream, the pancreas releases insulin, a hormone that directs other nearby cells to absorb the sugar. Muscle, fat and other cells then absorb the excess glucose from the blood and insulin levels eventually return to normal.
Meals high in sugar, have a higher "glycemic index". The glycemic index ranks foods as higher if blood sugar rises quickly and lower if the blood sugar rises slowly. So the higher the gylcemic index, the quicker blood glucose levels rise, but ultimately all carbohydrates will increase our blood glucose levels. Our bodies were made to use sugar as energy, but a high blood sugar is somewhat toxic and deleterious to our end organ systems (eyes, kidneys, heart, etc). When sensing a rise in blood sugar, insulin is released to promote glucose uptake at the cellular level. Muscles, fat cells, etc respond by taking in the glucose from our blood cells. The high insulin levels also weaken the activity of another hormone called glucagon - that typically is responsible for signaling the body to burn stored fuel. This means that the metabolism of fat and metabolism of sugars within our cells stop. So we go from normal blood sugar where body is burning fat, and glucose within cells to a state of change where we and storing glucose into fat and muscle with inability to metabolize sugars well into energy. As the cells are taking up blood sugars into their cellular matrixes, our overall glucose levels start to drop, and ultimately because there is still active insulin circulating our body, our blood sugar levels drop, often very low, leaving the body starved for energy. The body does not have a regulatory "glucose-stat" to stop the blood sugar from going too low, so it in fact plummets below it's "baseline" and the brain and intestines then send out hunger signals. New cravings are created requiring more carb intake. Our reactions are generally to reach for more carbs since they are readily available. and the up and down cycle repeats.
This is often a cause and effect that leads to overeating, that then generates more fat creation, rise in blood insulin level, more hunger, and more weight gain and the cycle goes on, and on.
On the contrary, adhering to a low carb diet puts an end to this cycle. There are NO ups and downs of blood sugars with a protein and green veggie diet. In general, reduced carbohydrates generally decrease insulin levels, increased glucagon levels, advance weight loss, improved triglycerides (fats carried in the blood which are necessary but when excessive cause coronary damage), decrease in LDL's (bad cholesterol), and increase in HDL's (good cholesterol).
Refined and processed carbohydrates which cause rapid changes in blood sugar, trigger hunger, thereby encouraging overeating that ultimately leads to obesity and smaller spots on your plate. Complex carbohydrates don't have as high a glycemic index, but unfortunately they do this as well. No one ever died from skipping potatoes, pasta, rice and white bread!