Ahhhhhh, Carbohydrates

Carbohydrates (carbs): Carbs are the first of the two "energy" nutrients. Each gram of carbs provide 4 calories. The main function of carbs in the body is to provide a quick source of fuel for physical and mental work. It can be stored in any of the three main storage units of the body: in the muscle and liver as glycogen but also as body fat.

Carbs are the body's preferred energy source, so if sufficient amounts of carbs are present in the diet, it's hard to "force" the body to use fat for fuel. In other words, if you eat a lot of carbs, your fat will remain where you last left it!

Carbs also cause the greatest insulin spike of all three main macronutrients (protein, carbs, fat). In fact, the elevation of blood sugar levels (carbs are sugar) is the main stimulus for insulin release. This is both a pro and a con: insulin, you recall, can help drive protein and carbs into the muscle (a Good Thing) but it can also stimulate fat storage (a Bad Thing). Furthermore, as long as insulin levels are elevated, it's next to impossible under normal circumstances to stimulate the release of fatty acids from the fat stores. This means that as long as insulin levels are high, fat loss is almost impossible. Remember also that when insulin levels are elevated it puts your body into "storage" mode.

So under certain circumstances elevated insulin is a good thing (when you need to shuttle in nutrients to your muscles ASAP) but most of the time it's not. The only two times you should have a lot of carbs (and thus spike insulin) are at breakfast, and right after a workout.

After you wake up, the breakfast insulin spike will help halt the catabolic (muscle wasting) state brought on by eight or more hours of fasting ("breakfast," of course, means "breaking the fast"). After a workout, the insulin spike will rapidly deliver the nutrients to the muscle. This will initiate the recovery and building process immediately, while countering the actions of cortisol. Keep in mind, however, that the amount of carbs you should have at these times will vary greatly depending on your goal and degree of leanness.

Any other time is not a good time to consume a significant amount of carbs, as the insulin elevation will have a negative impact on body composition. Your insulin level remains elevated for up to 4 or 5 hours after a carb-rich meal, which can bring fat loss to a standstill for this period of time. In other words, a high sugar meal will not only directly add fat to your body, it will also prevent fat use effectively, turning you into a fat storing machine.

Although carbs are your body's preferred fuel source, carbohydrates aren't essential the way many amino acids and fatty acids are essential. This means that you could function properly even on a diet of zerocarbs: the body would adapt to other fuel sources and you'd do just fine.

Carbohydrates come in many varieties. Without going into too much detail, every carbohydrate from pure sugar to whole wheat is turned into glucose in the body. The main difference is the speed at which it's turned into glucose. The faster it turns into glucose, the greater the insulin spike will be (because more glucose will enter the blood stream at once). The speed at which a carbohydrate (or any food, for that matter) elevates blood sugar is measured by the glycemic index (GI). Every food is given a specific GI number, and the higher the number is, the faster it elevates blood sugar levels. While not always perfectly accurate, it does give us a clue as to how much a food will affect insulin production.

But no need to be super scientific about it. If your goal is body composition in general, the following rule applies:

Must-have carb sources: green veggies (broccoli, cucumbers, lettuce, spinach, celery, asparagus, etc.)

Can-have carb sources: other veggies (except potatoes), berries (blueberries, raspberries, strawberries, blackberries, etc.)

Occasional carb sources: Other fruits

Rare carb sources: brown rice, whole wheat bread, whole wheat pasta, cream of wheat, potatoes, yams

Should-avoid carb sources: white bread, white pasta, oatmeal

Must-avoid carb source: pastries, cookies, candy and any other junk sugary food