Eating for Endurance

When I started cycling, my ultimate goal was to be able to ride a century. Riding a hundred miles seemed huge and very far away. I had no experience with endurance training and no idea how my body would react to that kind of physical pressure - emotional stress sure - but no idea where to begin. So I started riding more. My longest ride all those years ago was sixty miles, not insignificant, but not a sustained effort. I learned quickly that without proper fuel I would come home and crash, hard. My body would rebel and I would take at least a day to be functional. I don’t believe this experience is mine alone. Women are taught to eat less, to restrict our food, to watch what we eat, to ignore our internal rhythms, and to live in a calorie deficit. Add to this the complexity of our hormone cycle and the ridiculous amount of data that focuses solely on mens bodies and it’s no wonder we sometimes can’t find our way to a nourished, vibrant, and sustainable eating pattern that supports all of us and our goals. 

So let’s break down some of that confusion. I’ll talk about what works for me and what is backed by some of the best (and only) data on women’s sports nutrition. This is focused on women’s health but of course some of it is applicable to folks who don’t have ovaries. 

How to begin. Stand up to the narrative of shame that you might be holding onto around food. Remove yourself from the harmful notion that you are undeserving of nutrients or that you need to measure, monitor, or earn it. I’m serious. Your body is a glorious, beautiful, and powerful machine. Would you not charge your bikes battery because it ran out part way on your ride? Fuck no. You’d make sure that your batteries were fully charged and ready to go. So eat. Eat to support the life and activities you want. 

You cannot fuel yourself effectively without eating on the go. If you can drink water on the bike you can eat there too. Learn how to eat while you’re riding. This is huge. By the time you feel hungry enough to pull over it’s too late and you’re in a deficit. I’ve been there, I get it. You want to be done, you think you can make it the last ten or so miles - whatever the case may be. Any ride that lasts longer than 2 hours should see you snacking. When we take breaks to eat we run the risk of eating too much all at once. This can lead to tummy upset due to decreased blood flow in the gut and liver in support of cooling which impacts nutrient absorption, motility, and the integrity of the GI tract. Eat on the bike, small amounts often. 

My favorite method is to cut up bars (ProBars, Lara, Rx) and put them in a small plastic baggie in my top tube feed bag along with some pieces of jerky or another protein source. For rides over 50 miles I add in some gel blocks and electrolyte gummies. This method gives me variety to break up the miles and small mouthfuls that don’t overwhelm my gut. Its also a lot easier than fishing around in my pockets for a soggy bar and worrying about opening it and then losing the wrapper. Practice on shorter jaunts. Trust me, it’s worth the effort. Don’t just focus on simple sugars aka refined carbs. I see you gummy candy. These will taste delightful and help you for a few minutes but you need to balance them with protein and a little fat and fiber. Food is fuel here. Refined carbs and simple sugars spike your stress response and crash out your blood glucose. Keep it steady with a mix of macronutrients. 

Instead of setting a timer, I start eating at mile 20-25. I’ll have 2-3 bites of whatever is in the bag, and then each 5 miles I’ll have a few more, even if I’m not hungry. I’m looking at my mileage anyways and depending on how fast you are, 5 miles is 15-25 minutes which is perfect for allowing food to exit your stomach and not cause upset. If you’re faster than this, pick a mileage that resonates with you. When I do stop, I eat a bit more but I’m never ravenous. This allows me less time off the bike which is powerful in longer rides and a stable source of glucose and nutrients to keep me going comfortably. Eat more, stop less. It is also important to not overload your system with a large quantity of concentrated carbohydrates like gels or hydration mixes with more than 4% carbohydrate per serving. These pull fluid into the gut which causes diarrhea and can dysregulate your fluid balance.

So how much is enough? The general recommendation for an active woman is 40-45 calories per kg (pounds divided by 2.2) of body weight. Let’s be clear here - I hate calories. They are imprecise and are a driver for disordered eating (historically myself included), I mention them here only as an example and to encourage you to listen to your body and eat more. I weigh 59kg so for me 2360-2655 calories a day is sufficient. See that - over 2000. And definitely not 1200. I am not the exception. Listen to your body and eat until you’re full. If it causes you some anxiety to think about unrestricted eating or you’re concerned about your ability to recognize when you’ve eaten enough, let’s talk. 

One of the biggest issues women confront in sports nutrition is low energy availability (aka consistently not eating enough). This causes disruptions in luteinizing hormone pulsatility which impacts hypothalamic gonadotropin-releasing hormone which causes menstrual dysfunction. Irregular or absent menses along with abnormal pituitary signaling causes reductions in estradiol which is osteoprotective. This is true with or without loss of menses. That’s quite a mouthful; more plainly, your bones and heart depend on hormones to stay functioning effectively. Losing your menstrual cycle is a huge deal and often directly tied to lack of total nutrient intake. You need your menstrual cycle. And your menstrual cycle needs enough nutrients. Your body needs to feel safe in order to feel like it might want to get pregnant (you ABSOLUTELY do not need to have babies but your body doesn’t know this, thanks biology) and safety comes in the form of adequate nutrition. Low energy availability also increases cortisol and general inflammation, both of which are helpful in getting you to want to eat, but detrimental to training goals and life overall. 

As I mentioned above, we need all macronutrients. The one that gets the most play in sports is carbohydrates. This is with good reason, we literally run on glucose. However, women store and use carbohydrates differently than men. Shocking I know. All this time you’ve been told to train and eat the same. Mercifully data is catching up and we have good evidence that we are in fact, not smaller versions of folks with testes. We tend to need a more consistent intake to support our activity levels and this is increased in the luteal phase (after ovulation) of the menstrual cycle when gluconeogenesis (making glucose out of other substrates) rates are higher. Your body doesn’t process glucose the same and can end up feeling deprived as your metabolism is impaired. This is part of why you crave carbs later in your cycle, you actually need them.

Math wise, early in your cycle you need about .35 g/lb/hour of carbohydrate while riding. This increases to .45g/lb/hour in the luteal phase. Without enough carbohydrate we run the risk of fatiguing early and having impaired cognition due to low blood glucose.

What about carb loading? There is no good data to support carb loading in women. We burn fat and blood glucose rather than glycogen from our liver or muscle relative to men. Straight carb loading (big pasta dinner before an event or long ride) has been shown to boost glycogen in muscle tissue in men by up to 41% while women in the same study gained zero. Men’s lactate threshold also increased by 45% while women gained 5%. When overall intake of  macronutrients was increased the gap narrows to 17% women and 23% men. Eating enough is more important and more beneficial than carb loading. But, carb intake should increase with intensity and time. This should also correlate with overall energy intake. Light active or recovery day - 2.5 g/kg, rides 1-2 hours - 3-3.5 g/kg, rides 2-5 hours - 4.5-6 g/kg, 5+ hours - 6-7 g/kg. This makes sense. We burn more fuel so we need to fill the tank. Refined carbs will go up and out like a match. Mixed macros and complex carbs will burn much longer with less intensity. 

Cyclists tend to be carb lovers, I get it. But we also need protein. Progesterone is catabolic, meaning it’s literally breaking down your muscle tissue, and is higher in the luteal phase. We need 1-1.6 grams per pound of body weight daily and 30-40 g protein w/in 30 minutes of completing exercise to build, replace, and maintain muscle mass. Muscle mass is important as we age, to manage blood glucose, and keep us active. In addition, taking 5-7 grams of a BCAA’s or leucine prior to exercise helps reduce fatigue during training. I’m not advocating for a strictly high protein diet (no dry chicken breast please) but we do need to prioritize a balanced eating pattern that supports amino acid metabolism. 

While you’re riding its often helpful to minimize (but not avoid) fats. For general health you need at least 20% of your intake from fat (I tend to advocate for 30-35% for those with ovaries). However, fat slows transit time which can cause you to feel full but also heavy and nauseous on the bike which is exacerbated if you’re training in the heat. So get a little bit.

Another aspect of endurance riding is hydration. Folks with ovaries tend to be smaller which is important in thinking about the size of our internal organs and blood volume. It is vital that you keep your blood volume up via hydration so that your heart and lungs can perform effectively. I start hydrating in the days before a long effort. The night before I will increase my sodium and potassium intake so I have some reserve going into the day. This is especially helpful in the luteal phase or in heat. High estrogen and progesterone in the luteal phase cause fluid retention outside of your vasculature (bloating) and increase your core temperature by .5-1 degree Celsius. Your ability to hydrate and cool down effectively are significantly impacted. Hydration can also be an issue as the longer you exercise, the poorer your sense of thirst is. Aim for .4-.8 liters per hour and add electrolytes that focus on sodium and potassium. I’ve used Nuun, Liquid IV, and Trace Minerals with good results. 

Four years after I made the original goal to ride a century, I finally did. I rode and I ate and I listened to music and I had an amazing time. No headaches, no cramping, no bonking, just me vibing on my bike and finishing faster than I thought I would. I had energy at the end of the day and I wanted more. A month ago I completed the Seattle to Portland ride with the same energy and success. Riding distance doesn’t need to be scary or mysterious, you just need some good information and a little planning. 

Sources:

Sims, S. The Fine Art and Science of Fueling for Hot Races. Triathlete. July 12, 2022. Accessed July 26, 2023. https://www.triathlete.com/nutrition/the-fine-art-and-science-of-fueling-for-hot-races/

Holtzman B, Ackerman KE. Recommendations and Nutritional Considerations for Female Athletes: Health and Performance. Sports Med. 2021;51(Suppl 1):43-57. doi:10.1007/s40279-021-01508-8

Sims, S., Yeager, S. Roar: How to Match Your Food and Fitness to Your Unique Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life. Rodale Publishing. July 5, 2016.