I just did a quick calculation. Normal blood sugar level is always kept within a narrow range, about 4.4 to 6.1 mmol/L (82 to 110 mg/dL). We have about 5 liters of blood in our entire bodies. So if you round out the sugar content to about 90 mg per deciliter, it comes to about 0.09 g per liter. At 5 liters that means we have about 0.5 g of sugar in our blood stream at a normal blood sugar level.
If you look at food labels, you will be astounded by the amount of sugar we eat. A slice of bread can have 25 or 30 g of carbohydrates. Some of these will be fiber that is not absorbed, but most of it will be. A typical carb-heavy meal like breakfast with cereal, toast and a fruit juice jacks up the carb content pretty quick.
Blood sugar needs to be tightly regulated and can be become toxic if it goes too high. Eating foods loaded with sugar (carbohydrates) forces your body to deal with it immediately. When I eat, I make a conscious effort to avoid refined carbohydrates (breads, pastas, cereals, doughy foods like doughnuts) and sugary snacks and drinks. Take the time to read the labels and make a conscious effort to eat fewer carbohydrates, choosing foods that take longer to digest (steel cut oatmeal, brown rice, Quinoa).
Remember, it’s the sugar that will make you big and sick, not the fat. There are sugars in all foods (including fruits and vegetables), and your body can make sugar from your proteins. We actually have very little need for starches in our diets.