Nutrient Timing to Get the Most out of Physical Activity

By Daniel Heller, MSc, CSCS, RSCC

In Personalizing Nutrition for an Active Lifestyle, we discussed the importance of nutrition in relationship to different activities. Here, let’s discuss the specifics of timing, energy management, and the role of nutrient timing for recovery from different types of activities.

As you read, keep this question in mind: What are your goals and/or intentions for exercising and physical activity? The way you describe your lifestyle and activities can provide insights into how, and when, you should be eating to better support them. Research indicates the importance of understanding how nutrient timing affects performance¹ both in the gym and out in the wild. While some people work out daily to stay in shape, others are self-proclaimed “weekend warriors,” spending Monday through Friday preparing mentally for weekend adventures.

Gym sessions and physical activities have been separated below to help you get the most out of this article, regardless of where you spend your active time. As always, consult with your healthcare practitioner before beginning any exercise program.

Protein & resistance training

Hitting the gym during the week in anticipation of the weekend suggests your nutrient-timing focus should be on postworkout protein. Protein delivery can be in the form of a supplement (powder, premade drink, or protein bar), high-protein snack, or complete meal. Taking a supplement makes the intake of 15 to 25 grams (1.2-17 grams per kilogram of body weight) of protein convenient, quick, and easy to digest, and evidence indicates there is no harm in consuming more than this suggested amount.² The importance of consuming protein postresistance training is twofold. The first is to replace muscle protein breakdown (MPB) caused by lifting weights that occurs normally during resistance training. The second is to support muscle protein synthesis (MPS), which is the building of muscle following resistance training. The role of protein intake is to make sure you have a greater MPS to MPB ratio.² Amino acid profiles of the protein sources are also important because specific essential amino acids such as leucine have been linked to increased MPS. For those types of gym sessions, which should be around 60 to 75 minutes, water can suffice for hydration.

 Carbohydrates & endurance

A common term that has been used to describe the speed at which carbohydrates are delivered as usable energy is “glycemic load.”* The delivery speed of the carbohydrate consumed plays an important role in determining how long an endurance-type of physical activity can be performed and how quickly recovery can take place afterward.

High-energy carbohydrates enter the blood stream quickly, providing energy for higher intensity activities, while lower energy carbohydrates are absorbed slower, enabling longer performance at a lower intensity. The energy level of the carbohydrate consumed should match the intensity of the activity. However, one can only absorb so much of a particular type of carbohydrate at a time. Intake of 60 to 90 grams of carbohydrates per hour of activity is a safe estimate.³

When you’re deciding on your carb source, identify the type of sugar in your favorite culinary delight. For example, when a label reads sugar (glucose) and fructose, this means there are two types of carbohydrate that will be transported via separate transport mechanisms. What sets high- versus low-energy carbohydrates apart is the transport process. For example, glucose (high-energy) is transported via sodium-dependent transporter called sodium-glucose-linked transporter 1 (SGLT1), while fructose (low-energy) is absorbed through another sodium-dependent transport called glucose transporter 5 GLUT5.⁴ When SGLT1 becomes saturated and cannot move any more glucose through, fructose can still enter the system by way of GLUT5, which in turn increases the total amount of carbohydrate you can digest within an hour to maintain the intensity of your physical activity. A note about fructose: If too much is ingested too quickly, it has the potential to cause gastrointestinal upset. If preparing for a competition, it is important to practice nutrient timing as part of the routine for competition preparation.

Reflecting back on the question posed in the beginning: What are your goals and/or intentions? If your current goal is to drop a few pounds, you might want to consider eating a slightly lower number of calories than your total energy expenditure. If you’re trying to break a personal best time on a specific run distance, try incorporating more high-energy carbohydrates into your prerun meal. You may have to play with and adjust the timing, as the optimal time could be anywhere from 2 hours to 30 minutes before your run. Finally, consume protein following your resistance training workout if your goal is to build muscle. Your window here is about 20 minutes to a couple of hours.

The bottom line is that the way we eat should fit our lifestyle, our tastes, desires, and goals. These nutrient timing guidelines do not negate the importance of a whole-food diet.

Until next time, live well and live active