Firstly to ensure your overall marathon training diet is balanced, read Nutrient Balance for Athletic Performance. You also need to figure out what you can / should eat before each run. During your training, use this time to practice what you will eat on race morning.
Don’t overdo it
You may not need to eat before every training run. My rule of thumb is I don’t take in any calories if the run is under 10 miles (unless the workout is a speed workout or other intense session).
You want to start each workout fully fueled. Think about how long you are running and what energy it will take to get you through the workout. If I am running 10 miles or less first thing in the morning I will have a banana before leaving home OR a sports gel just before the run starts. (assuming I am driving to a group run) Between 10-14 miles I base my decision on what I had for dinner the night before and if I have any hunger. Over 14 miles I follow the suggestions below.
For your weekly runs if you run after work, follow these instructions. You will probably be running 5-7 hours after lunch which will approximate the overnight fast.
Your objectives during your training season are to:
- find out what works for you and
- stay optimally fueled for the workout.
Beyond that, there is a school of thought that you need to teach your body to use nutrients wisely by running on “empty” occasionally.
When planning your marathon training schedule, also plan when / what you plan to eat.
When planning what to eat before your run think about these things:
Satisfy your hunger
This seems obvious but is so often overlooked. If you run first thing in the morning, don’t skip breakfast. You need to BREAK the FAST to fuel your workout.
How much you eat depends on the distance / intensity of your workout.
Skipping breakfast can make it harder to maintain your blood sugar level and can deplete your limited stores of carb muscle fuel (glycogen) even faster. This can hamper your ability to get in a full workout and reduce the effectiveness of your training.
If you have trouble eating first thing in the morning, get over it. This is mostly a mental problem and you can overcome it.
One method to get over the problem of not being able to eat first thing in the morning is to have a liquid breafast. You can blend a smoothie or try Ensure High Protein drink. You can find this is the baby section of most grocery stores.
Replenish carb stores
The second goal is to restock your carb stores. This is most important for early morning runners
During the night your body works to repair tissue and regenerate cells. All of this work creates energy demands during the night. Plus you were breathing and digesting dinner. The most readily available source of energy is glycogen. This is your precious energy source you stored up in your muscles for your morning run. By the time you get up your carbohydrate store has been reduced by 140 – 260 calories. That should give you an idea of how much you need to eat before your run.
As mentioned earlier, the longer the workout the more important this is. The idea is to replenish carbohydrate fuel stores without overtaxing your digestive system.
Reestablish fluid levels
During the night you likely lost as much as ounces of fluid. Replace this to ensure you start your workout hydrated.
Every workout has a training stimulus. Or it least it should. Suppose you have a 8 mile tempo run on your schedule. The training stimulus of a tempo run is increasing one’s lactate threshold. If you start the run depleted, it is highly unlikely you will train at your optimum level, thereby missing the improvement in your training you were supposed to get from the tempo run.
Prepare for recovery
Recovery is one of the most overlooked aspects of training. Yet it can be the difference in dragging through workouts and sailing through them. We will have a separate discussion on recovery nutrition but for now understand that if you start the workout depleted, your recovery will be affected.
You can set yourself up to recover quickly by starting each workout optimally fueled.
Those are the general pre-workout nutrition goals.
What are the specific recommendations for eating before marathon training?
Try to take in 200 – 300 calories for every hour between now and when you run
If your run is starting at 7:30 and you get up at 6:30, eat 200 – 300 calories. If you can get up at 5:30, then you can take in more. What did you have for dinner last night and when did you eat? This will make a difference in how many calories you will want in the morning.
Eat mostly carbohydrates
Since your goal is to replenish glycogen stores, it makes sense to eat the foods that will most easily be converted to glycogen – carbohydrates. If you choose the right carbs, your food will digest quickly and you won’t be carrying it around in your gut during the run.
Eat from the low end of the glycemic Index
The Glycemic Index (GI) has to do with how fast the carbohydrates in a food are digested and absorbed into the bloodstream.
You have two decisions to make regarding the GI of your pre-run snack.
- High GI – blood sugar crash
- Lower GI – tend to have fiber and might be hard to digest quickly
Low GI foods are generally not ideal in the pre-exercise meal. Since these foods are processed more slowly by your digestive system and typically contain more fiber, the danger is that you could end up with gastrointestinal discomfort while running. (This is why you practice what you plan to eat. An apple might work for you while be too much fiber for your neighbor.)
- Lower GI – give the food time to digest
- Higher GI – eat immediately before running
Keep your pre-run food low in fiber
As just mentioned, lower GI foods are often high in fiber. That fiber will absorb the water in your gut and swell. Not what you want during your long run.
Include some protein
It’s wise to include a bit of protein in your pre-run meal.
Several studies show that a mix of essential amino acids (protein) and carbs taken before strenuous exercise stimulates protein synthesis after exercise. This is great news for endurance training as it sets you up for recovery.
Even without the promising results from the studies, the protein will blunt the affect of a high GI food, delaying the release of sugar into the bloodstream and delaying fatigue.
Surely you know this by now. Don’t start your run at risk for dehydration. Research has shown beginning your workout fully hydrated may reduce protein breakdown during training. If you are not sure why this is important, google “ammonia smell during exercise”.
Water only the last hour before your run
Many marathoners guzzle Gatorade in the last hour before the race (or training run) but this is not ideal. The sugar in sports drinks sends sugar into the bloodstream, followed by the release of insulin to control it. Such a reaction is likely to leave you low on blood sugar at the start of the run.
However, 10 minutes before your run, go ahead and have that Gatorade. When the insulin rush happens you will be running and the exercise will blunt the effect.
If you need some help choosing foods that fit this profile, read this article titled “Ideal pre-marathon foods“. In addition to ensuring your overall marathon training diet is sound, you need to monitor what you eat before each run. During your training, use this time to practice what you will eat on race morning.