Nutrient Timing Basics

Previous blogs discussed the benefits of carbohydrates in terms of being a primary source of energy, protein-sparing, and nutrient timing (link to your blog entry, as suggestion to encourage visitors to read other articles in the company blog). These concepts are complementary, in that the overlap as a viable energy source varies with timing of exercise (before, during, after), as well as the interaction between macronutrients, namely carbohydrates and protein.

Usually, we would want to avoid foods with a higher glycemic index (GI), since these carbohydrate-containing foods will quickly raise blood glucose levels. A person with a diet consisting of high GI foods has an increased risk of diabetes, heart disease and some cancers. However, in the window before a workout, say 30 minutes prior, a pre-exercise high GI snack can provide the energy to sustain yourself through the entire workout. This is due, in part, to the fact that ingesting carbohydrates spares the muscle glycogen (stored carbohydrate) already present in your body. If your activity or sport utilizes a lot of glycogen, such as soccer, high intensity interval training (HIIT) or other go-stop-go activities, then a pre-exercise high GI snack is a must in order to not deplete glycogen stores rapidly.

During exercise, carbohydrate intake can improve performance. Resistance exercise, for example, benefits by providing the energy to lift, as well as assisting amino acid transport (the building blocks of protein) into the muscle to support muscle repair. When carbohydrate levels are high, insulin is produced, which works as an anabolic hormone to carry protein into the muscle cells. As an added benefit during training, muscle cells are more receptive to insulin during periods of increased workload.

The recovery period starts as soon upon completion of the workout, and may persist for up to 24 hours. During this time, carbohydrate intake is very important to replace the depleted glycogen stores in your muscles. And just like during the workout, insulin is hard at work to deliver glycogen to your muscles to prepare you for the next workout. Just like pre-workout, ingesting a high GI food is beneficial. Later in the recovery period, switching over to a lower GI food source makes sense, so as not to spike insulin levels unnecessarily.