Have you ever wondered if eating at specific times mattered? Does science truly exist behind the manipulation of specific foods and feeding times? Well, the answer is yes… it's called nutrient timing. Nutrient timing is defined as the "manipulation of nutrient consumption at specific times in and around exercise bouts to improve performance, recovery, and adaptation." As implied in the definition, nutrient timing is mostly used to augment physiological responses to exercise and promote recovery (I.E., muscle strength, body composition, substrate utilization, power, and physical performance). Let’s break down and discuss what nutrient timing is and how it can benefit not only your weight and nutrient goals but your overall fitness performance as well.
WHAT IS NUTRIENT TIMING?
To effectively implement nutrient timing, an understanding of macronutrient metabolism, energy systems, and exercise physiology is important. The metabolic rates of proteins, fats, and carbohydrates during rest, exercise, and recovery are imperative to science. While nutrient timing has developed to include recommendations in 24 hours, specific windows before, during, and after training are largely the focus since many athletes are involved in multiple pieces of training/competitions per day, and frequently experience small windows of opportunity for feedings.
THE SCIENCE BEHIND TIMING
While research on the manipulation of fats exists, specific timing strategies have yet to show clear and repeated success when augmenting performance or recovery. Pre-workout windows largely focus on 3-time points: consumption 4-6 hours before exercise, 30-60 minutes before exercise, and/or 15 minutes before exercise. These windows focus largely on glycogen availability in the muscles, or how saturated the muscles are with carbohydrates. It also considers the digestion and absorption rate of specific nutrients, and substrate utilization during exercise. Moderate to high-intensity exercise relies heavily on carbohydrates as a fuel source, however, glycogen stores in the body are limited and can only supply the body with energy for up to a few hours during continued high-intensity bouts. Therefore, "filling up the gas tank" is imperative to improve performance and prevent fatigue. It takes roughly about 4-6 hours for carbohydrates to be fully digested and assimilated into muscle and liver glycogen. Therefore, the first feeding priority before exercise is a meal at least 4 hours before competition to fully saturate muscle glycogen stores. It is often recommended to consume 1-4g/kg of carbohydrates at this mealtime before engaging in high-intensity exercise (>70% of Vo2 max) lasting greater than 90 minutes.
The purpose of post-workout feedings at specific times is to augment the recovery process, which in turn implies muscle recovery. Muscle recovery goals will vary based on the sport an athlete is participating in but can include muscle strength, muscle growth, or prevention of muscle soreness. Since muscles store carbohydrates and amino acids make up the structure of skeletal tissues, feedings are largely focused on carbohydrates and proteins. When studies compared the effects of carbohydrate or protein feedings on muscle protein synthesis, they found that together they have the greatest effect on increasing muscle protein synthesis. Regarding promoting recovery, it is suggested that following intense exercise an individual should consume 1g/kg of carbohydrates and 0.5g/kg of protein within 30 minutes after exercise and continue to feed carbohydrates at a rate of 0.7-1.2g/kg/hour to accelerate glycogen re-synthesis.
MUSCLE GROWTH AND STRENGTH
Regarding muscle strength and growth, it has been found that the greatest effect of protein consumption is largely dependent on the last dose consumed. Regular protein feedings every 3-4 hours in doses of 20-40 grams have shown the greatest benefit in improving muscle growth, and strength and leading to favorable changes in body composition. However, regarding specific feeding windows, muscle protein synthesis is greatest immediately after up to 2 hours post-exercise. How much protein should be consumed in that time frame? 20-40 grams or 0.25-0.4g/kg! Can essential amino acids also do the trick? Yes! Doses of 10-12g of essential amino acids can also maximally stimulate muscle protein synthesis.
IMPROVED ATHLETIC PERFORMANCE
Before exercise, consumption of at least 30-60g of carbohydrates + 5-10g of protein about 30-60 minutes before exercise leads to improved exercise performance and increases in amino acid availability. This can improve recovery and leads to favorable changes in body composition such as increases or maintenance in lean mass and decreases in fat mass. During exercise, frequent feedings of 30-60g of high GI carbs per hour of training can help increase performance, maintain normal blood glucose levels, and prevent early fatigue. Post-exercise, protein should be consumed as soon as possible after exercise. However, you can still maximally stimulate muscle protein synthesis up to 2 hours post-exercise by consuming 20-40g of a rich protein. When it comes to strength, recovery, and improved body composition it is recommended that protein be consumed in intervals of every 3-4 hours to promote a positive state of nitrogen balance. If your goal is to build muscle, carbohydrates, and protein should be consumed together. Aiming for at least 1g/kg of carbohydrate + 0.5g/kg of protein will maximally stimulate muscle protein synthesis. Nutrient timing can be employed at any level, however, if you are looking to gain a competitive edge and boost your performance, nutrient timing may be the key to your success.