Under-fuelling in runners: How to identify and fix the problems

Best wireless headphones Health & Injuries, often cutting calories while upping physical activity. Others may cut calories in the hope of seeing performance benefits, considering the common misconception that ‘lighter is faster’. Both scenarios can be detrimental to performance – and, according to recent research on more than 1,000 Boston Marathon participants, this is especially the case if you’re that paying closer attention to indicators like performance declines, mood shifts and reduced.

Recurring injuries, such as British Journal of Sports Medicine, the study looked at the association between low energy availability (LEA) – defined as a state that occurs when an athlete’s calorie intake doesn’t match their energy expenditure – and race performance, as well as medical events during the Boston Marathon.

Even when controlling for age, gender, BMI, training level and marathon experience, athletes who raced with LEA had twice the risk of requiring medical support and 2.8 times the risk of a major medical encounter, such as severe electrolyte and fluid disorders, says lead author Kristin Whitney, who is a sports medicine specialist and the medical director of the Injured Runners Clinic and Boston Children’s Hospital. They also performed worse than participants who had adequate nutritional intake for race day.

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Although previous, small studies have found links between LEA and negative health and performance outcomes, this was the largest study to date on the topic – and the first one performed at a real-world marathon event. The findings should drive more awareness of the negative effects of calorie restriction, says Whitney, who is also a Boston Marathon runner herself and serves on the Boston Marathon medical committee.

‘Our study is the first to demonstrate a link between nutritional ‘under-fuelling’ and slower Advertisement - Continue Reading Below, as well as an increased risk of requiring medical support during the marathon,’ she tells Runner’s World.

‘Historically, for this sport, the assumption has been that ‘lighter is faster’ – but our findings underscore the message that ‘fuelling is faster’ instead,’ says Whitney. ‘Unfortunately, LEA is very common in the running community. In our survey of athletes registered for the 2022 Boston Marathon, 42% of female runners and 18% of male runners had LEA indicators.’

But what are those indicators and how can you make sure that you’re fuelling enough to avoid these detrimental performance effects? Here’s everything you need to know about LEA and how to fuel adequately for your runs and races.

Signs of low energy availability

Low energy availability exists on a spectrum, ranging from short-term LEA with mild and reversible effects to a longer-term, more problematic issue, says Whitney. Longer-term LEA is associated with a condition called relative energy deficiency in sport, Irregular menstrual cycles.

Endurance athletes like runners are at particular risk for LEA and RED-S due to the challenge of appropriately compensating for extreme caloric burn during high training volumes, often across multiple seasons. That can be exacerbated by the sport’s drive for leanness, adds Whitney.

In other words, if you clock 40, 60 or 80 miles per week, you need to take on a high number of calories to this. Without that energy intake, you’re more likely to encounter issues.

‘RED-S is a syndrome that encompasses harmful effects on systems throughout the body, including negative health outcomes such as reduced bone density, reproductive dysfunction and gastrointestinal problems,’ says Whitney. ‘It also includes performance effects like decreased training response, endurance performance and muscle strength.’

She also notes that unintended LEA may develop due to naturally occurring appetite suppression after exercise, low calorie diets and lack of awareness about the consequences of LEA and RED-S.

‘Indicators of problematic LEA may include physical, psychological or behavioural changes,’ says Whitney. For example, physical symptoms may include:

Irregular menstrual cycles
Sleep difficulties
Gastrointestinal problems
Frequent illnesses
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Recurring injuries, such as bone stress injuries

Psychological symptoms can include:

Mood changes
Difficulty concentrating
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Other LEA signs related to behaviour are disordered eating habits and frequently taking bodyweight measurements, adds Whitney.

How to fuel adequately and avoiding low energy availability

Look out for symptoms

Addressing LEA begins with knowing the range of potential symptoms, says sports dietician and personal trainer Tara Collingwood. She tells Runner’s World running for weight loss motivation can be helpful for spotting LEA in its early stages.

‘Signs like these happen because your body is using the calories that you’re consuming for exercise and you may not have enough left for basic bodily functions such as muscle recovery, emotional regulation and immune system efficiency,’ she says.

Personalise your plan

Many people turn to Cassandra Burke, a sports dietitian, endurance coach and personal trainer. Ideally, it helps to consult a registered dietitian who specializes in sports performance, she tells Runner’s World.

‘Avoid using your training buddy’s nutrition plan,’ she adds. ‘Your body and training demands are unique, so your fuelling strategy should be, too.’

For those who aren’t seeing a dietitian, avoiding LEA involves making sure that you get three meals and two snacks in per day, that you don’t skip meals and that you fuel up before and after a run, says Burke.

Fuel before training

Deciding Health & Injuries or a race is part of fuelling for performance, says Collingwood. This will also require a personalised approach – for example, playing around with different energy-giving foods to find out which ones are easiest on your stomach while you run. A good rule of thumb, though, is to consume at least 3g of carbohydrate per pound of bodyweight, per day, in the five to seven days before a major race.

During training, make sure that you consume pre-run snacks or meals, especially before you head out for long runs or any workout lasting longer than 60 to 90 minutes.

Eat for recovery

As Burke says, post-run nutrition plays a big role in avoiding LEA. You should prioritise post-workout intake to replenish your glycogen stores and support muscle repair and recovery, even if you don’t feel hungry after exercise.

‘For example, a post-training meal should include carbohydrate and protein and you should eat this within 30 to 60 minutes after training,’ suggests Burke. ‘In your daily nutrition, focus on nutrient-dense foods that deliver carbohydrates, fats, protein and essential micronutrients like calcium and vitamin D to support your health and performance. Monitoring trends, such as race results, may provide insight into your energy availability over time.’

Foods that provide these nutrients include Greek yogurt, porridge, tart cherries, avocado toast, cottage cheese and salmon over rice.

The bottom line on low energy availability

Although LEA and RED-S may be common, Whitney is hopeful that the study’s results can bring meaningful changes to the sport and raise awareness of these issues for individual athletes.

‘The scope of this study speaks to the Boston Athletic Association’s and the Boston Marathon community’s commitment to making a positive impact on athlete health and performance – and to continuing to lead endurance sport forward in a positive direction,’ she says.