There is a right time to eat—not only for general activities of daily life, but specifically for pre, mid, and post-workout nutrition. Eating at the right times will give your body the fuel required to push through a challenging workout, activate fatty acids for energy burning, and promote muscle growth.
The International Society of Sports Nutrition (ISSN) recently published an objective, critical review with a full list of details to help you know when to time your consumption of macronutrients. The paper is focused on healthy, exercising adults, providing a full breakdown of how, when, and what to eat in order to maximize body composition and exercise performance.
Nutrient timing is described as “the purposeful ingestion of all types of nutrients at various times throughout the day to favorably impact the adaptive response to acute and chronic exercise (i.e., muscle strength and power, body composition, substrate utilization, and physical performance, etc.).”
Note: This paper focuses entirely on the uptake of proteins and carbohydrates, as the “research examining a specific timing question (for fats) has yet to take shape.” The manipulation of carbs and fat intake is the subject of a great deal of ongoing research, so the ISSN has not included definitive recommendations at this time.
Here are the ISSN’s recommendations for nutrient consumption and the most effective timing of those nutrients:
How much carbs? Carbs are the primary energy source for resistance workouts and moderate to high-intensity endurance activities. The body can only store 380 to 500 calories of glycogen at a time, which limits available fuel during high-intensity resistance training and aerobic exercise. Declining glycogen levels decreases the athlete’s ability to maintain exercise intensity, and causes a reduction in work output.
The recommendation for high-performance athletes is 5–12 grams of carbs per kilogram of bodyweight per day (g/kg/day). Those who train at moderate to high intensity for upwards of 12 hours per week should consume no less than eight g/kg/day in order to maximize glycogen storage.
For a quick glycogen refuel: If you require a rapid restoration of glycogen, there are three routes recommended:
- Aggressive carb loading/refeeding (1.2 g/kg/h), primarily focusing on high glycemic index foods (above 70 GI).
- Caffeine supplementation, roughly 3 to 8 milligrams per kilogram of body weight
- Pairing carbs with protein—carbs: 0.8 g/kg/h, protein: 0.2–0.4 g/kg/h
Adding protein to carbohydrates increases glycogen resynthesis rate, which could minimize muscle damage, accelerate recovery after intense physical exercise, and promote a favorable hormone balance.
Extended High-Intensity Exercise and Carbohydrate Timing
For athletes who engage in more than 60 minutes of high-intensity exercise (above 70% VO2Max), glycogen stores and fluid levels will be sorely depleted. Thus, the ISSN recommends consuming 30 to 60 grams of carbohydrates per hour, preferably in the form of a 6-8% carbohydrate-electrolyte solution. Six-twelve fluid ounces should be consumed every ten to 15 minutes throughout the exercise bout, especially for those that extend beyond 70 minutes.
Increasing carbohydrate intake (along with increased fluid intake) will help to reduce muscle damage, facilitate re-synthesis of glycogen, normalize blood glucose levels, and improve performance.
Resistance Training and Carbohydrate Timing
Research has indicated that consuming carbohydrates during resistance training exercise can help to increase glycogen stores and normalize blood glucose levels. For workouts of three to six sets of 8-12 reps targeting all major muscle groups, it’s recommended to consume either carbohydrates or a combination of carbohydrates and protein throughout the training. This can lead to greater chronic and acute training adaptation, improve muscle glycogen uptake, and reduce muscle damage.
Protein consumption during workouts can heighten the body’s adaptation to exercise and is recommended for those who perform high volumes of exercise.
Protein Throughout the Day
For healthy individuals who engage in physical exercise throughout the day, the ISSN recommends that you place extra emphasis on meeting your total daily intake of protein.
Protein feedings should be spaced out at intervals of three hours to maximally stimulate protein synthesis in the muscles. Consuming 20 to 40 grams of protein (0.25–0.40 g/kg body mass/dose) at a time (every three to four hours) has been proven to maximize muscle protein synthesis compared to other dietary patterns. Not only will this protein intake improve exercise performance, but it can also have visible improvements on body composition (lean body mass versus fat mass).
In regards to essential amino acids, a minimum of ten grams at a time (included in a protein bolus of 20 to 40 grams) has been proven to maximize muscle protein synthesis.
Pre-workout meals may have an impact on the amount of protein required post-exercise. If sufficient protein is consumed prior to a workout, there may be less call for post-workout protein. However, a combination of pre and post-workout consumption of protein or protein plus carbs can lead to visible strength increases and body composition improvements. Post-workout protein consumption should take place no more than two hours after the workout in order to maximize muscle protein synthesis.
Consuming a casein protein supplement (30 to 40 grams) before bed can improve both metabolism and muscle protein synthesis, but will not influence the breakdown of lipids (lipolysis).
When to Eat
The ISSN’s recommendations focus on athletic and exercising individuals, but it indicates that changing the frequency of meals (to every three to four hours) can improve satiety and regulate appetite even among those who do not exercise. However, in non-exercise scenarios, changing up meal times will have limited impact on body composition and weight loss.
In regards to meal structures, the recommendations are:
- Big breakfast
- Decent-sized lunch
- Small dinner
One study found that obese/overweight women who consumed more calories at breakfast lost 2.5 times as much weight as women who consumed high-calorie dinners.
Reference:
1. Chad M. Kerksick, Shawn Arent, Brad J. Schoenfeld, Jeffrey R. Stout, Bill Campbell, Colin D. Wilborn, Lem Taylor, Doug Kalman, Abbie E. Smith-Ryan, Richard B. Kreider, Darryn Willoughby, Paul J. Arciero, Trisha A. VanDusseldorp, Michael J. Ormsbee, Robert Wildman, Mike Greenwood, Tim N. Ziegenfuss, Alan A. Aragon and Jose Antonio. “International society of sports nutrition position stand: nutrient timing.” Journal of the International Society of Sports Nutrition201714:33.
