This is one of those posts where when I begin to write it, I think to myself "Why have I had a blog this long and not made this post" but nevertheless here it is today! I normally stay away from this topic and just give general guidelines for marathon training nutrition because it's so individual (as everything right!) It's hard to give out this information without that person being a personal client of mine.
Before I get into the good stuff, I wanted to give some disclaimers. The recommendations for this are kind of crazy so you might find yourself thinking that you can't eat that much. I think it's important to realize two things. 1) You have trained and most likely trained your nutrition as well, so you want to stick with what has worked for you for your long runs 2) Science and studies are only good if we can also use logic and our brains to work through those things.
Studies are wonderful, but just because a study is there doesn't mean that it's going to be the golden rule for you. On the contrary, just because there isn't a study out there for something doesn't mean that it doesn't work. Use critical thinking and if you think that it will help you, then wonderful!
THE GOOD STUFF
Week leading up to Marathon:
So now that I've talked enough about that, let's move on to the recommendations. You may to consume approximately 3-4g per pound of body weight in carbs starting 3 days out from the marathon. For example, if you were a 120 pound girl, then you would want to consume 360-480g carb. This is obviously a lot (ranging from 1440 calories (360x4cal/g) or 1920 calories (480 x 4cal/g) and that's not including your protein and fat. Therefore, you want to accommodate for this and lower your protein and fat so that you aren't just like putting on excess weight. I would say that maybe you could aim in the middle of these two around 1600 calories of carb and make that 75-85% of your daily calories. That means that your total calories in carb (this is my example for 120 lb girl) would be 1600 (400g). If that makes up 85% of your calories, then the other 15% of calories would be divided between protein and fat and totaling 1882 calories for the day. (1882 x 0.85 = 1600) If you are going backwards to find your total calories then just take your weight x 3.5 = total g of carb. Take that total g of carb x 4 = total calories in carbs. Total calories in carbs divided by 0.85 = total calories for the day!
Once you have your total calories for the day, then you can just divide it evenly in protein and fat. It really doesn't matter all that much. The best way to go about this honestly is if you already know your general caloric intake for the day. I would suggest taking your normal and just switching around the balance. You might would add in like 100-200 extra calories, but nothing excessive. You are tapering so you aren't using that much glycogen and by shifting the balance to 85% carb you are going to fill up those tanks! :)
DAY BEFORE MARATHON:
I'm not going to go into the micros that you need today, but this is important. You want to make sure that you are intaking good foods and electrolytes, and water. You don't want to just drink water only because you could flush out your electrolytes, and that's never a good thing. You want both. Eat salt tablets like candy. You can never really have too much, but too little is bad news bears. Make sure to get potassium and magnesium as well. TAKE A MULTIVITAMIN because chances are, you probably will need more than you'll eat!
I don't recommend that anyone count the day before a marathon. First off, I think that's borderline obsessive, but also because this should be a time that you are relaxing and not worrying about every little gram. I tell my clients normally to eat whatever they want when they are hungry and to aim for dense carbs and fat. You don't want to be eating "diet foods" the day before a marathon, but you don't want to be stuffed either. I always have a meal that is really high in calories, but I just stop when I'm full. You see so many people that have huge bowls of pasta with muffins and such. That's all wonderful if your body is used to that type of volume, and can handle it. I would be sick. I normally love a good sandwich with some protein on it with french fries. French fries are high in fat and carb and last me through the rest of the night. I normally have a small snack before bed.
MORNING OF MARATHON:
The recommendations will tell you if you google that you should wake up at like 3am and have a big breakfast so that it has time to digest before your start. Maybe the pros do this, and maybe you are cool like that, but I would much rather have my sleep then worry about waking up to eat. NO THANK YOU!
The rule of thumb is that whatever you have in the morning when you wake up, you want that to be a long digesting carb. For example, oatmeal. In all honesty, I have the same breakfast I always do which is protein waffles with peanut butter! HA! Again, you don't want to be overly stuffed and your glycogen should be stored from the days leading up to the marathon as well.
Right before you start, you want something that is a fast digesting carb, and this is going to be something like a banana or a cliff bar or a bagel! I know a lot of people have like half of a bagel with peanut butter and a banana. That's a perfect snack right at the start line. It allows you to start off feeling fueled and wonderful!
I think that everyone has a general plan going into the marathon of what they are going to do based on their long runs. You don't want to change this. I've wrote some articles about nutrition for marathons, but generally the rule of thumb is to take in 100 calories every hour which means that if the marathon takes you 4 hours to complete, then you would take in 4 gus (one gu has 25g C and 100 calories). You don't want to save these until the end but rather space them out evenly. You might take a gu at mile 5 and think that you don't need it but it will translate to more energy later on in the race. If you aren't used to taking in that many gus on your long runs, then that's okay and you have to do what works best for you. If you normally take in 250calories per hour which is what I hear from some, then that's fine and you should do that. As much as we love guidelines, we are all very different!!
I hope this gives you a little more insight into what I do, and what you should leading up to a marathon. I'm taking this same approach nutritionally leading up to my half ironman as well. Today, I'm doing my shift to 85% carb so bring on the cereal, bagels, potatoes, and fruit! :)