Debbie J., MS, RD contributed this article –
Think of the carbohydrate as the fuel for the fire. It is the prime energy source for your muscles and brain. The carbohydrate is actually a group of short and long sugar links. Like coal briquettes, single units of sugar can be burned to create ATP. These sugar units can be found freely as “simple sugars” (e.g. in milk, juice, soda and candy) with a sweet taste or linked together as “complex carbohydrates” (e.g. in potatoes, vegetables, grains, beans) with a starchy taste. The longer chains are digested and broken down into single units, but this takes time and energy.
Here is why it matters which kind you are eating… The complex carbohydrates are bulkier, more filling, and slower to digest. They satisfy longer than simple sugars for the same amount of calories. Because they take longer to digest, complex carbohydrates cause a moderate slow rise in blood sugar requiring less insulin response. This means less of a storage signal on your fat deposits – yay! The net effect on your waistline is potentially less carbs converted to fat and more available to burn as long as you’re in energy balance and move those muscles.
Compare – 2 Cups of orange juice (200 Calories, 45 gm carbohydrate, 37 gm sugar, 1 gm fiber) with 2 Cups of pasta and vegetables (210 Calories, 42 gm carbohydrate, 4 gm sugar, 7 gm fiber) They will both fill you up with the same volume, but the juice will cause a higher blood sugar spike, insulin rush and compensatory storage with subsequent hunger. The pasta and vegetables will be absorbed slowly, give sustained energy and satisfy you longer.
Hence the idea behind “slow carbs.” Even among the starches when you can replace refined white flour products with the whole grains you are choosing more complex chains that are tougher for your digestion to break down. For example, beans are a better choice than saltine crackers for accompanying a salad.