“I’m never hungry after a run, is it OK to wait several hours before eating?”
This is not a straightforward answer since it depends on your training schedule and goals. Researchers have often referred to the post exercise timeframe when muscle protein synthesis (MPS) and glycogen synthesis (glycogenesis) are most rapid as the ‘anabolic window’. In other words, this is the time when muscles are more sensitive in building/ repairing muscle and replenishing their carbohydrate stores. The two macronutrients of highest concern for rapid recovery are carbohydrate and protein. Carbohydrate stores, as liver and muscle glycogen, are limited and depleted fairly quickly during exercise (depending on the duration and intensity); while muscle proteins are also broken down or damaged. Therefore, rapid replenishment of both carbohydrate and protein post exercise is desirable, but there are several considerations to make before you stress about eating your post-run meal within the first hour of finishing your run!
Carbohydrate and Timing
In regards to timing carbohydrate consumption post exercise, the ‘anabolic window’ (~1-2 hours post exercise timeframe when glycogen synthesis is most rapid) is only necessary to consider when the time between workouts is <8hours. Whereas, when there is >8 hours between workouts, the specific timing of post exercise carbohydrate ingestion is not necessary to fully replenish stores if total daily carbohydrates are met.
If your training sessions are <8 hours apart (that is, the next session starting <8 hours from finishing the last one), timing is important. It is recommended to consume 1-1.2 g/kg/hr for the first 4 hours post exercise, followed by the general carbohydrate recommendation- considering pre-exercise guidelines and meeting your total daily carbohydrate needs.
If your training sessions are >8 hours apart, timing of carbohydrate ingestion is not important since the time between workouts is sufficient enough for full replenishment. However, as mentioned above, meeting total daily carbohydrate needs is critical. This is good news for those athletes who don’t have an appetite after a run and for those who have always stressed about eating your post run meal in that ‘anabolic window’.
Protein and Timing
The ‘anabolic window’ may have more popularity among athletes involved in resistance training due to muscle protein synthesis (MPS) being most rapid within 1 hour post resistance exercise, but protein ingestion post exercise should also be a consideration for endurance athletes.
Consuming protein before, during, or after exercise may attenuate muscle damage, spare muscle glycogen, and increase glycogen synthesis. Inclusion of protein post exercise has benefits on MPS and on glycogen stores, when consumed with carbohydrates.
If your goal is to increase muscle mass or strength by resistance training exercises, you would benefit from consuming ~20 g or 0.25-0.3g/kg protein within the first hour of resistance training exercise. Maximizing muscle adaptation from training may be best accomplished by consuming ~20g or -.25-0.3 g/kg after resistance training exercises and then again with another meal(s) every 3–5 hours. With endurance training, getting protein within ~1 hour is less important, but should still be part of your post workout meal. The inclusion of protein with carbohydrates can increase glycogen synthesis, so focus on the timing of carbohydrates (per guidelines above), and include ~20 g or 0.25-0.3g/kg protein with your carbs! Keep in mind that including carbohydrates post workout of any kind is a good idea since glycogen is also used in resistance training.
For an estimate of your carbohydrate and protein needs post work-out, see the following pages: Protein and Carbohydrate
Sodium, Fluids, and Timing
As discussed above, carbohydrate and protein are critical for recovery, and timing of ingestion post exercise may be beneficial in some situations. Additionally, sodium and fluid needs should also be considered in your post exercise refueling strategies. The post workout meal is a good way to both rehydrate and consume sodium to replenish losses accrued during exercise. The timing of sodium and/or fluid replenishment may be important depending on the amount lost (without repletion). If you are not able to eat a balanced meal (that contains sodium) post exercise, when losses are moderate/ high, make sure you consume the amount of fluids you lost during exercise, and sodium if necessary; sports beverages will usually do the trick! Check out the hydration and electrolyte page to understand your fluid and electrolyte needs.