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The body can store only a limited supply of carbohydrates. If you went without eating, your carbohydrates would be depleted within a day, whereas fats would last you a few days, maybe more. As a result, you need to ingest carbs frequently, but you don’t need a diet high in them to get the energy you need. Glucose can also be broken down from muscle, and you’ll learn later in this chapter how fat can provide you with plenty of energy (known as fat adaptation). Carbs can be used in five different metabolic pathways to provide ATP for movement:

•Glycogenesis: glucose to stored glycogen

•Glycogenolysis: glycogen to glucose

•Glycolysis: glucose to pyruvate

•Krebs cycle and electron transport chain: acetyl-CoA to ATP, CO₂, and H₂O

•Gluconeogenesis: noncarbohydrates to glucose

GLYCEMIC INDEX

The glycemic index of a food is a measure of how quickly the food increases blood glucose. Table sugar gets a score of 100, and all other foods are calculated relative to this score. Glycemic index can be a useful guide for understanding which foods cause blood glucose spikes; however, it is all relative, and it depends on the serving size of the food and the food combinations. In general, to have a healthy body composition and optimal athletic performance, eat as many foods with a lower glycemic index as possible, such as legumes, vegetables, fruits, and whole grains.

High-glycemic foods—such as sugar, breakfast cereals, and white bread—spike blood glucose and as a consequence also spike insulin levels. Low-glycemic foods—such as legumes, most fruits, and nonstarchy vegetables—tend to be digested at a much slower rate. This is excellent for performance—you feel more satiated, micronutrients are absorbed better, more fiber is ingested, blood sugar and insulin levels are better controlled, your muscles can repair faster, energy levels stay consistent during activity, and your performance improves. A diet abundant in high-glycemic, fast-acting carbs can make you feel sluggish and hungry, with inconsistent energy levels, leaving you to bonk or rapidly drop in blood glucose levels during activity. The best time to eat these types of carbs is during or right after exercise when insulin is the most sensitive and when muscles are hungry for more glucose.

Slow-digesting carbs have dietary fiber, which is very important for gut health, cholesterol levels, and healthy bowel movements. You want to get a minimum of 25 grams of fiber each day from both soluble and insoluble fiber (found in beans, legumes, dark leafy greens, and green beans). Higher fiber intake is preferable and has been shown to reduce the risk of colon cancer, heart disease, diabetes, and insulin resistance.

Dietary carbohydrates are all broken down to glucose in the blood. The body then takes it up and stores it as glycogen (glycogenesis). When you start to work out, and your body needs energy, it breaks down glycogen to form glucose (glycogenolysis) and then further breaks the glucose down into pyruvate (glycolysis) if the activity is intense enough to provide your cells with ATP. If the exercise is reasonably moderate and long duration, pyruvate is converted into acetyl-CoA (and joined to oxaloacetate, a by-product of carbohydrate metabolism) and shuttled into the Krebs cycle inside the mitochondria to produce a mass amount of ATP for endurance exercise. The last pathway for the body to get ATP and glucose is through gluconeogenesis—basically, a backup system for supplying glucose to the brain, in which the liver converts stored glycogen into glucose, or converts fats and protein into glucose. This is what typically happens during low-carbohydrate diets. If there are times when gluconeogenesis can’t happen, the liver will create ketone bodies.

RECIPES FOR LOW-GLYCEMIC MEALS

•Applewood-Smoked Pulled Pork and Beans

•Carrot Currant Slaw

•Marinated Kale with Artichokes and Mozzarella

•Smashed Cucumber Salad

•Avocado Green Machine Smoothie

Carbs are not evil. These days, carbs have the same reputation that fat used to have (and sometimes still has). Just looking at carbs can make you gain weight. False! Don’t be afraid of carbs, or any other food for that matter. Have positive thoughts about food. If you don’t, they can snowball into negative thoughts about other foods, your body image, and other people’s eating habits. Stay positive, and for Pete’s sake, eat some carbs.