When Is The Best Time to Eat Before a Workout? (A Review of the Science & Evidence)
Let’s take a few minutes to talk about how to time your pre-workout meal. The metabolic activity and demands of your body after you eat versus when you exercise are different. It requires an understanding of how that works to appreciate how to time your meal. Additionally, your goals are the gym are another influential factor in determining how to time your meal; for example are you looking to lose weight and burn fat or to gain muscle?
This all starts with a basic understanding of the autonomic nervous system. It’s extraordinarily complicated and I did my best to summarize that in another lecture. If the autonomic nervous system, sympathetic and parasympathetic state are new to you; I would encourage you to watch that video. It will help you understand what’s happening to your body when you exercise versus when you eat a meal. If you think you have a good understanding of how it works, feel free to continue watching.
Autonomic Nervous Systemic & Workout Explained: https://youtu.be/OOEUJftQQHw
Let's look at the research..
A 2003 study looking at the effects of varying amounts of pre-exercise carbohydrates found that “ the ingestion of 0, 25, 75 or 200 g of glucose 45 min before a 20 min submaximal exercise bout did not affect subsequent performance.”
Another 2003 study looking at the effects of timing of pre-exercise carbohydrates on metabolism and performance concluded “Altering the timing of the ingestion of carbohydrate before exercise resulted in differences in plasma glucose/insulin responses which disappeared within 10 min of exercise and which had no effect on performance.”
2008 study looking at effects of different glycemic index pre-exercise meals on running performance “in conclusion, our results indicate that compared with an isocaloric high GI meal, the consumption of a low GI meal 2 h before a 21-km performance run is a more effective means of improving performance time.”
A 2010 study looking at the effects of a high- versus low- glycemic index meal prior to exercise concluded “The low GI meal led to an increase in the availability of carbohydrate and a greater carbohydrate oxidation throughout the exercise period, which may have sustained energy production towards the end of exercise and led to the improved TT performance observed.” (For those who don’t know about glycemix index, lower GI usually indicates more complex carbs although that’s definitely not a hard and fast rule)
A 2010 meta analysis looking at the myths surrounding pre-exercise carbohydrate feeding concluded “ that advice to avoid carbohydrate feeding in the hour before exercise is unfounded. Nevertheless athletes may develop symptoms similar to those of hypoglycaemia, even though they are rarely linked to actual low glucose concentrations. An individual approach may therefore be necessary to minimize these symptoms even though they do not appear to be related to exercise performance.”
2011 study looking at effects of low glycemic index and high glycemic index food on running capacity concluded “results suggest that lentils, the LGI food, ingested 15 min before prolonged exercise maintained euglycemia during exercise and enhanced endurance running capacity.”
A very interesting 2012 study looked at the effects of a high fat meal after 3 days of carb loading on endurance performance and concluded “following 3 days of glycogen loading, a HFM and subsequent ingestion of a small portion of carbohydrate jelly prior to exercise enhances the performance of athlete endurance running.”
The research on the subject is somewhat underwhelming.
It appears that low glycemic index meals are better than high glycemic index meals (i.e. complex carbs are better fuel than simple carbs). You can also loosely conclude that the amount and timing of carbs under one hour may not influence performance. Unfortunately, there are too many other variables in that equation such as intensity and duration of workout, people don’t usually eat strait glucose, etc, etc to really draw any hard conclusions.
One other thing to mention is rebound hypoglycemia. This is a real phenomena. If you eat too many carbs prior to exercising, it can lead to hyperglycemia and hyperinsulinemia and subsequent rebound hypoglycemia 15-30 after you start exercising. Keep that in mind.
Here are a few more things you should know before I draw the conclusions.
Regarding macros, carbs are digested the fastest, followed by protein then fat. Carbohydrates translate most directly to energy during working out; they are utilized most readily by skeletal muscle.
The closer you get to your workout, the simpler your meal should be. This will help you avoid getting stuck in a parasympathetic state (rest & digest) and allow your body to mobilize the simple sugars.
Your goal(s) at the gym should dictate when you eat. There’s a big difference between building muscle and strength and trying to burn calories and fat and lose weight.
Ok so in conclusion: How do you time it properly?
- Large meals. Eat these at least three to four hours before exercising. This can consist of whatever macro nutrient combination you want: simple or complex carbs, protein and/or fat.
- Small meals. Eat these two before exercising. You should begin leaning towards simple carbs, moderate in protein and relatively low in fat. This can help facilitate gastric emptying, minimize gastrointestinal distress, and help maintain blood sugar.
- Small snacks. Eat these an hour before exercising. This meal should be much closer to a small sugary snack with minimal amounts of fat or protein.
Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance. European Journal of Applied Physiology (2003). Jentjens et al.
Effects of timing of pre-exercise ingestion of carbohydrate on subsequent metabolism and cycling performance. European Journal of Applied Physiology (2003). Moseley et al.
Effect of the glycaemic index of a pre-exercise meal on metabolism and cycling time trial performance. Journal of Science and Sports Medicine (2010). Moore et al.
The Myths Surrounding Pre-Exercise Carbohydrate Feeding. Annals of Nutrition and Metabolism (2010). Jeukendrup et al.
Significant Effect of a Pre-Exercise High-Fat Meal after a 3-Day High-Carbohydrate Diet on Endurance Performance. Nutrients (2012). Murakami et al.
The Effects of Pre-Exercise Glycemic Index Food on Running Capacity. International Journal of Sports Medicine (2011). Karamanolis et al.
Effect of the glycaemic index of pre-exercise carbohydrate meals on running performance. European Journal of Sports Science (2008). Wong et al.