Understanding carbs, insulin and their relation to energy and body fat.
The ratio of macronutrients (protein, carbohydrate and fat) in the meals you eat is the key to being lean, muscular and maintaining optimal health. Managing your food intake is a powerful way to control the way you look and how you feel. Perhaps the greatest current controversy comes from the fight over how much carbohydrate you should eat to maintain a lean, healthy and sexy body.
Carbohydrates are different types of sugars linked together in chains of different lengths. We need carbohydrates to fuel our bodies for energy and to feed our brain, which uses glucose (a simple form of sugar) as its primary energy source.
Fact: The brain is a glucose hog, using more than two thirds of the circulating carbohydrates in your bloodstream while at rest.
This primary body fuel is mainly provided as you digest the carbs you eat, breaking them down into usable glucose molecules. Then your body rebuilds the simple glucose molecules into longer chains called glycogen for more efficient storage. The body has two places to store glycogen: the liver and the muscles. The liver acts as the reserve supply for the muscles. When the muscle glycogen gets low, the liver sends glycogen back into the bloodstream so it can be shuttled back to the muscles.
The liver's capacity to store carbohydrates in the form of glycogen is very limited and can be easily depleted within ten to twelve hours. So the blood glucose (blood sugar) and the liver's glycogen reserves must be maintained on a continual basis. This is why it is necessary to eat carbohydrates regularly.
What happens when you eat too much carbohydrate?
The average person can store approximately 300-400 grams of carbohydrate in your muscles and about another 75-100 grams in the liver. For comparison, 100 grams of carbs is equivalent to about 2 cups of cooked pasta. When both the liver and muscles are glycogen full, excess carbohydrates are stored in adipose tissue or body fat.
In greater detail;
1. The carbs you eat are digested or broken down by enzymes into simple glucose molecules.
2. Your body will attempt to shuttle glucose into the muscles and liver for energy use. Moreover, excess glucose entering the blood after a meal is rapidly taken up by the liver and stored as the large polymer, glycogen (via a process called glycogenesis).
3. Whatever excess glucose is not needed by the body for energy at that time is taken from the blood by the hormone insulin and converted by the liver into a highly compact energy storage molecule called a triglyceride (fat) via a process called lipogenesis. Fat has over double the storage efficiency of carbs as it holds 9 calories of energy per gram versus only 4 calories per gram in carbohydrate form.
Why the type of carbohydrate you eat matters.
Even though carbohydrates are fat-free, excess carbs you eat can become body fat. The type of carbohydrate is also a key factor in avoiding body fat gain. In other words, the speed at which you digest carbohydrates into glucose can dramatically affect whether the food you eat becomes body fat. As a genral rule, a more refined and less fibrous carbohydrate will be broken down more easily and quickly, causing a rapid rise in blood glucose. For example, simple carbs such as cookies and candy digest quickly whereas complex carbs such as oatmeal digest much more slowly giving the body time to manage the influx of glucose more effectively.
Examples of "good" or complex carbs include:
leafy green vegetables
Examples of "bad" or simple carbs include:
(highly processed and refined foods, leaving them with fewer nutrients than whole grains. Refined grains also lack the fiber of whole grains, so they're not likely to fill you up quickly.)
many types of candy
For comparison examples:
Choose brown rice over white rice as it contains more fiber
Choose 9-grain bread over white bread as it digests 100% slower
Choose yams or sweet potatoes over white potatoes as it digests 100% slower
choose an apple as a snack over a banana as it digests nearly 65% slower
TIP: Adding vegetables to any meal adds fiber, which slows digestion and helps minimize the increase in insulin.
When your glucose level rises too rapidly after eating, your body reacts quickly to remove the excess blood sugar. As stated above, to adjust for this rapid rise, the pancreas secretes the hormone insulin into the bloodstream. Insulin then lowers the levels of blood glucose via the mechanism explained above. So, eating junk foods regularly can result in continuous, high levels of insulin. Continuously high levels of insulin can cause an aggressive accumulation of body fat. Furthermore, the constant barrage of insulin on your cells can make them insulin resistant making it difficult to maintain optimal cellular nutrient levels. This condition can also lead to the disease diabetes.
Furthermore, a high insulin level suppresses two important hormones: glucagon and growth hormone. Glucagon promotes the burning of fat and sugar. Growth hormone is vital for muscular development.
The heavy insulin reaction to a rapid rise in blood glucose can also cause hunger and cravings. What you feel is the burst of energy as your blood sugar rises following a carbohydrate meal and the resulting energy crash as insulin causes a subsequent rapid depletion of blood sugar. As your energy crashes your brain begins to crave sugary foods as the fastest way to correct your now low blood sugar. And so begins the vicious fat promoting cycle. This see-saw effect on your blood sugar can be very dangerous. So while insulin is critical to metabolism, managing it properly helps maintain optimal health.
The goal is therefore to eat more complex or slowly digesting carbs (those with a lower Gylcemic Index and higher fiber content) and limit sugary foods to help stabilize or modulate your blood sugar and the hormone insulin. As a result of doing so, you are far less likely to store body fat and help to instead utilize more body fat for energy use.
As a tip, eating good or unsaturated fats with carbs also helps slow digestion.
Examples of "good" or unsaturated fats include:
Nuts and seeds
Examples of "bad" or saturated fats include:
- Add olive oil and vinegar to your salad instead of a more saturated fat dressing such as ranch or blue cheese
- Dip vegetables in yogurt versus cheese
- Add a little natural peanut butter to rice cakes for a snack
- Add beans to any carb meal to slow digestion
1. Bodybuilding.com 2003; Carbs and Insulin
2. ExRx.com 2003 ;Complex Carbs VS. Simple Carbs