New Year’s Resolution: Eat More

It’s January, and as an ultrarunner, you’ve likely been busy locking in your 2025 race schedule and mapping out your goals for the year. That goal-setting probably revolves around race times, total mileage and elevation gain, or finally tackling that bucket-list route that’s been calling your name. But this year, what if you did things a little bit differently? What if you set a goal that is actually the key to crushing big mileage and setting PRs? What if your goal was simply to eat enough?

According to a 2024 study, over 40% of trail runners are at risk of something called low energy availability (LEA).

LEA is defined as a state of “inadequate energy intake to support basic physiological processes after energy expenditure from exercise has been accounted for.” In other words, not eating enough to support your activity level. LEA is the primary cause of Relative Energy Deficiency in Sport (REDs) – more on that later.

There are a lot of reasons why you might not meet your calorie needs as an ultrarunner. While many ultrarunners would deny it, there is still a prevalent “race weight” culture in this sport that focuses on being as lean as possible or “looking fit”. Disordered eating and eating disorders are rampant, with some studies finding as many as half of runners may have eating disorders – but in many cases, under-fueling is not intentional (sources: 1, 2, 3). Even with a perfectly healthy relationship with food, you may still be at risk of REDs.

The reality is, ultrarunners have high energy needs, and practically speaking, keeping up with them can feel downright impossible. This is especially true for those juggling peak training with work and family responsibilities. Fueling often ends up on the backburner, and it’s easy to see why.

But in 2025 (and beyond), what if you made fueling a top priority? Read on to discover why you should add eating more to your list of New Year’s Resolutions – and get practical strategies for meeting your nutritional needs while balancing training, work, and life.

Symptoms of Running on Empty

So, we know that LEA causes REDs, but what is REDs? REDs is a syndrome (a group of symptoms that commonly occur together) resulting from LEA. And these symptoms are bad news… Fundamentally, when your body doesn’t have enough energy available (when you aren’t eating enough to meet your needs), it starts to shut down everything that isn’t essential. Think about a phone running on low battery. In low battery mode, your phone does whatever it can to reduce power usage, like dimming the screen, going to sleep after a short time of inactivity, and slowing down the processor. Your phone still works at 5%, but not very well.

In your body, this shows up in a number of ways:

🥱 Low energy levels

A calorie is a unit of energy, so when calorie intake is low, so are energy levels. Some fatigue is normal, especially while sustaining high training volumes, but being unable to peel yourself off of the couch after a long run or to make it through the day without a nap is not normal.

🤕 Frequent injuries

When available energy is low, bone and tendon health take a backseat, which, when coupled with continued training, can result in bone stress injuries and osteopenia/osteoporosis as well as lingering soft tissue injuries.

🩸 Reproductive dysfunction

If you aren’t able to support your own body’s processes, you can’t support those of another. Your body starts to shut down reproductive function, resulting in menstrual irregularities, low testosterone levels, and low libido (in both men and women).

💩 Gastrointestinal, cardiovascular, and immune system dysfunction

Just like your phone in low power mode slows its processor, your body in a state of LEA slows digestion and heart rate and pulls power away from your immune system. The result is unpleasant GI issues, a weak heart that is less able to pump oxygen to your muscles, and frequent illness.

😞 Depression and anxiety

When your body doesn’t have enough calories, it doesn’t prioritize production of dopamine and serotonin – neurotransmitters that make you happy. LEA also triggers the body’s stress response, leading to higher cortisol levels and anxiety.

🤬 Irritability

Low energy availability puts you in a long-term state of hangry.

🪞 Preoccupation with food and body image

For the half of trail runners who struggle with disordered eating, this one seems obvious. But don’t think you’re off the hook just because you have a healthy relationship with food. When you aren’t eating enough, your body forces you to think about food as a means of forcing you to actually eat more.

If you’re constantly sick and injured and your body doesn’t have any extra energy to spare, it should come as no surprise that your performance will suffer.

Training outcomes of REDs include:

• Poor recovery: Repairing muscle and replenishing glycogen stores requires a lot of energy. A post-run protein shake is only a bandaid if you aren’t eating enough.
• Decreased endurance, strength, and power: Performance isn’t a priority for a starved body. You may be able to check off your miles, but nailing your workouts might be another story.
• Poor performance and training adaptations: Even if you’re making it through all of your workouts, you may find that your race performance is not as expected. This is because, without adequate energy, your body can’t adapt to training (meaning, your muscles aren’t producing more mitochondria, your VO2 max isn’t budging, and your heart isn’t becoming more efficient at pumping blood).

Key Strategies to Avoid REDs

When it comes to REDs, the best treatment is prevention. Although the risks of under-fueling are significant, the good news is that preventing REDs and staying healthy and injury-free boils down to a few very unsexy strategies:

1. Eat enough calories

By now, this should be clear: to avoid REDs, you must eat enough. If you aren’t eating enough calories, it doesn’t matter how many antioxidants you eat or how carefully you choose ingredients you can pronounce… you are at risk.

Calorie needs vary greatly from person to person and depend not only on activity level but also body size, muscle mass, and individual genetic and metabolic factors. Because of this, it is very difficult to offer a general recommendation. If you’re worried you may not be meeting your calorie needs, consider scheduling a session with a sports dietitian.

2. Eat enough carbohydrates

While eating enough calories is essential, it may not be sufficient to prevent REDs. Research indicates that even athletes who eat enough total calories can be at risk if they don’t eat enough carbs. This condition, known as low carbohydrate availability (LCA), can lead to outcomes similar to those seen in REDs. This is because carbs are the muscles’ and the brain’s preferred source of energy… and ultrarunners need a lot of energy.

Most ultrarunners will need between 2 and 5 grams of carbs per pound of body weight each day to support training and recovery. For a 150 pound runner, this is the equivalent of about 35 slices of bread per day. When it comes to low-carb diets like keto, just say no.

3. Eat consistently

Our bodies are constantly at work, repairing muscle, rebuilding bone, producing hormones, circulating blood, breathing, and so on. All of these vital processes require a steady supply of energy. While our bodies can store energy in fat, athletes thrive on a consistent stream of fuel from food. The more hours you spend in a relative calorie deficit – in other words, the more time you spend burning calories but not eating them – the greater your risk of bone stress injuries, menstrual dysfunction, and illness. Sound familiar? This is a concept known as “within-day energy deficiency” and it can occur even if your total calorie intake is sufficient. For this reason, Intermittent Fasting is not runner-friendly. Aim to eat a meal or snack every 3-5 hours while you are awake.

How to Eat More (Without Overthinking It)

Feeling overwhelmed? Take a deep breath. Fueling enough can feel really scary but it doesn’t need to be complicated. Here are some simple, practical tips to help meet your needs without stress:

• Eat early, eat often: A favorite race-day fueling mantra applies to day-to-day nutrition too. Eat breakfast within an hour of waking up and then continue to eat every 3-5 hours after that.
• Fasted is NOT faster: The research on fasted training hasn’t panned out. It increases injury risk (remember the within-day energy deficit from earlier?), makes it harder to meet your energy needs (before and during a run are critical opportunities to fuel), and doesn’t actually make you any faster. Aim for 40-80 grams of carbs before your morning workouts.
• Don’t skimp on the intra-run fueling: We are running through a carb revolution where elite ultrarunners are taking in as many as 130 grams of carbs per hour during races. Do the rest of us mere mortals need that much? No. But the less you eat on the run, the deeper the hole you dig yourself into – and the harder it will be to climb out. Rather than eating the bare minimum, what if you pushed your boundaries to take in as much as possible? 60-90 grams per hour is a good goal for most of us.
• Think liquid: Just as a sports drink may go down easier at hour 12 of an ultra, liquids such as smoothies or juice may be an easier source of fuel for those moments at home that you really don’t feel like chewing.
• Simple carbs are your friend: Do whatever you have to do to eat enough. I would rather you eat a bowl of ice cream every single day than put yourself in a state of LEA.

Conclusion

Researchers at Harvard University recently examined the link between LEA and race performance at the 2022 Boston Marathon, and the results come as no surprise: a large proportion of runners –  42.5% of women and 17.6% of men – are at risk of LEA. But here’s the kicker: runners with LEA finished nearly 500 places lower than those who were properly fueled, even after adjusting for things like body composition and training history. That’s 500 positions you could gain (and who knows what percentage in your Ultrasignup score) – without running a single extra mile or doing a second more of speedwork. The only thing you’d have to do differently is eat more.

In 2025, whether you’re aiming to toe the line of your first 100 miler, chasing a 50K PR, or simply wanting to play outside more, fueling is a game-changer. Make 2025 the year that you fuel up and eat enough. The research is clear: fueled is faster.

Alyssa Leib, MS, RD is a registered dietitian and owner of Peak to Peak Nutrition. She works with runners and mountain athletes of all levels to help them dial in their nutrition to perform and feel their best. She believes that every athlete deserves to fuel to meet their potential in sport and in life.