Your workout is complete and now the real race begins. As you wipe off the last bead of sweat from your forehead, you rush to the locker room to grab your shaker bottle. Your “anabolic window” is closing so you chug your protein mix before you even sit down to catch your breath. 

Does this sound familiar? As trainers and athletes, we have been told for years that nutrient timing is crucial and that we are “wasting our workout” unless we ingest a post-workout shake immediately. The classic nutrient timing train of thought has been to consume carbohydrate before a workout and protein afterward. While this approach is logical, is it supported by current research? 

Some may argue that we actually have it backwards, and that protein is more effective prior to a workout. Furthermore, timing is not crucial as long as we consume adequate calories and nutrients within a 24-hour period. 

To help clear up some of the confusion, here’s what you need to know about nutrient timing. 

Digestion and Absorption

Digestion, which is the process of breaking large food molecules into smaller ones, takes place primarily in the stomach. Absorption, which is the process of up-taking nutrients into the blood stream and lymph system, takes place primarily in the small intestine. Utilizing nutrients (carbohydrate, fat, protein, water, vitamins and minerals) is directly related to the rate of gastric emptying, which is the time it takes to digest foods and release them from the stomach into the intestines. Meals that are high in protein, fat or fiber and concentrated meals stay in the stomach longer and therefore absorb more slowly. Carbohydrates, liquids and semi-solid foods leave the stomach relatively quickly and absorb more rapidly. 

Enzymes at Work

Enzymes are proteins that speed up reactions in the body and are essential components to digestion as well as exercise metabolism. Physical activity triggers a number of reactions in the body and activates enzymes such as glycogen phosphorylase and glycogen synthase, which are responsible for turning glucose (blood sugar) into glycogen (stored carbohydrate). These enzymes remain active in the muscles for 30 to 60 minutes following exercise, and fuel consumed within this window can restore glycogen twice as fast as a meal consumed two hours later. The aforementioned anabolic window is a result of heightened enzyme activity following a workout. During this time frame, your body is more likely to turn your shake or food into carbohydrate (both in the muscles and liver) rather than fat. 

The Roles of Carbohydrate and Protein

Intense or long-duration exercise depletes muscle glycogen and breaks down muscle tissue (protein). Therefore, the goal of post-exercise fueling is to replace muscle glycogen and begin regenerating muscle tissue. Adequate carbohydrate and protein feeding post-exercise helps restore glycogen and protein stores, respectively. An important consideration, however, is how long it takes to utilize the energy we consume; carbohydrate can digest, absorb and subsequently raise blood glucose within 15 to 30 minutes. Protein, on the other hand, digests more slowly and does not lead to peak amino acid levels in the blood for up to three hours. Thus, consuming protein two to three hours before the end of your workout (one to two hours prior, in most cases) could result in more rapid tissue regeneration post-workout. 

But protein still plays an important role post-exercise, as it helps carbohydrate with its role. The addition of protein to carbohydrate increases insulin production. Insulin is a hormone that facilitates the uptake and storage of carbohydrates and amino acids (read more about hormones here). Thus, you can restore glycogen more quickly and prepare for your next workout, when you consume a combination of carbohydrate and protein (and for the record, a few grams of fat does not delay absorption significantly). 

The conclusion: Both carbohydrate and protein are valuable before and after workouts. 

Real Foods vs. Supplements

A recent trend in fitness and athletics is a push for real food instead of pills, powders and bars. Supplement manufacturers lead you to believe that liquid calories are superior to solid foods because they are absorbed more rapidly. And in a laboratory setting, this may be the case. But the only reason to use a supplement over a food is convenience. Few of us have live-in chefs and all of us have busy schedules, so quite often carrying a bar or shaker bottle are the only viable options. When you do have the opportunity to prepare a meal, the extra digestion time (compared to a shake) will not hinder glycogen or protein resynthesis. In fact lean meats, fruits, vegetables and whole grains have the benefit of more vitamins, minerals and antioxidants than the contents of your shaker bottle (and may be considerably less expensive). 

Transportable food options such as chocolate milk, fruit, yogurt, trail mix, homemade energy bars and sandwiches may provide the best of both worlds. As whole foods, they are nutrient dense and unprocessed, yet easy to take to the office or gym. High-water foods such as melons, apples, pears, cucumbers and bell peppers provide the benefit of assisting with re-hydration as well (but you still need to drink water before, during, and after exercise). 

A quick note regarding chocolate milk, which some tout as the best post-workout option. Low-fat chocolate milk has a great ratio of macronutrients, provides vitamins and minerals and is incredibly cost-effective. However, most of the research involving chocolate milk is flawed (as it has been compared to lower-calorie drinks) and it is no more or less effective than a similar drink or food providing the same amount of calories, carbohydrates and protein. 

Energy Balance

Your goals are an incredibly important consideration when making pre-, during, and post-workout food choices. Two different people, for example—one with weight-loss aspirations, one with healthy weight gain ambitions—should have two different fueling plans. For a weight-loss plan, total calories and carbohydrate should be less compared to a hypertrophy plan; protein, however, should remain relatively constant (see below for more details). 

Practical Recommendations

Research studies will recommend something to the effect of “consume 1.2 grams of carbohydrate per kilogram of body weight immediately following exercise and then each hour thereafter for four to six hours post exercise.” Or, “to maximize muscle protein synthesis, consume 0.4 grams of protein per kilogram immediately following exercise.” These numbers are accurate, but the implementation is incredibly unpractical. No one lives in a laboratory and almost no one measures every ounce of food or calculates carbohydrates and proteins down to the tenth of a gram. For a 160-pound individual (with the goal of maintaining or gaining weight), these recommendations boil down to 90 grams of carbohydrate and 30 grams of protein (a 3:1 carbohydrate-to-protein ratio).

Take-home Messages

• Consume a combination of carbohydrates and protein before and after workouts.
• Consuming 20 to 30 grams of protein (pre- and post-workout) is effective for muscle protein resynthesis.
• If the goal is to maintain or gain weight, consume a combination of carbohydrate and protein before and after workouts, with a 3:1 or 4:1 carbohydrate-to-protein ratio.
• If the goal is to lose weight, also consume a combination of carbohydrate and protein before and after workouts, with a 1:1 or 2:1 carbohydrate-to-protein ratio.
• Always hydrate before, during and after workouts.
• Supplements provide convenience, but real food provides better overall nutrients.
• Choose foods or supplements that work for you.
• Allow enough time before a workout for food to settle.
• The perfect ratio of nutrients is meaningless if you do not like the taste, cannot afford the product or experience gastrointestinal discomfort.