“Should I try to lose weight to run faster? When I was younger I lost weight and ran fast and then stopped having my menstrual cycle and had stress fractures. I never ran that fast again. How skinny should I be for maximal performance? My running buddies are constantly trying a new diet to lose weight. Should I be trying that also?
It is really common, especially among women, to want to be skinnier, both to fit an unrealistic societal ideal and perform better. Wouldn’t it be nice if there was a single resource or equation we could use to know exactly which weight would get us our best performance? Unfortunately, it is more complicated.
Many women are working against themselves and hurting their performance by trying diets and attempting to lose weight instead of using a mindset of fueling their body for performance and practice. This misguided attempt to lose weight to perform better may be counterproductive. Instead of getting faster, a relative energy deficit develops and leads to decreased performance and if severe, can lead to lifelong health conditions.
Relative energy deficiency does affect both women and men, but this article focuses on women (this is the women’s issue after all). If you have heard of the female athlete triad in past years, you could think of relative emergency deficiency in sport (RED-S) as an updated concept.
Components of RED-S are multifactorial. Usually, the condition starts with an athlete not consuming enough calories to meet their caloric loss during training. There are some complicated equations for calculation but the basic calculation is:
Energy Availability = Energy Input — Energy output
Energy input is calories consumed.
Energy output is the calories used for daily living and the calories used in exercise.
It is estimated that an EA (Energy availability) of 45 kcal/kg /FFM/day is sufficient. (FFM is fat-free mass in kg). It is also estimated that an EA of less than 30 kcal/kg/FFM/day is likely to lead to the body becoming stressed.
When the body has low EA it is affected in many ways. A low EA leads to changes in the hypothalamus and stops the LH (luteinizing hormone) surge that prompts menses. With a loss of the normal hormonal changes leading to menses, there is also less estrogen produced. This lack of estrogen leads to bone reabsorption and can lead to osteoporosis and stress fractures. Fatigue is common due to a decreased metabolic rate and training becomes harder and injury more likely. It is difficult to build muscles due to a lack of amino acids and proteins. Mental health changes include decreased judgment and irritability and many athletes can become depressed. The symptoms can overlap with overtraining and this can be difficult to differentiate.
Immunity is affected by low EA because catecholamines (epinephrine and norepinephrine) are suppressed. These hormones regulate immune responses. There are some studies showing higher susceptibility to colds and illnesses among athletes with low EA.
If eating disorders are present, the gastrointestinal system can be adversely affected. There can be constipation and slow digestion. Excessive use of laxatives and diuretics cause problems with bowel and also with electrolyte balance. There are also studies showing high cholesterol and triglycerides in athletes with EA. There is also evidence that low EA in a high-fat low-carb diet is worse than a higher carb diet.
If you are worried about an energy deficit what should you do? First, take a look at where you are at. What is the mindset of your current training buddies or your club? Is it supportive of many different body types? Is the prevailing attitude one that encourages lower weight above all? If there is not a healthy mindset, you might need to change workout partners. Most adult clubs are supportive of a healthy fueling perspective.
You may need to see a sports physician and check basic labs and hormones. If an energy deficiency is caught early, there may be little to no abnormalities and this can be reversed easily. If the body has been deficient for a longer time, there may be hormonal changes, (FSH, LH, and prolactin), low hemoglobin (anemia), elevated markers of inflammation (CRP and ESR), abnormalities of kidney or liver function. A bone density scan (DEXA) may need to be done to evaluate bone density. AN EKG may need to be done to rule out any cardiac issues. Working with a sports nutritionist may be helpful in identifying deficient areas and getting back on track for proper fueling. Even in the early stages of energy deficiency, nutrition is a key component and many females find that a few sessions with a good sports nutritionist are extremely valuable.
Most female athletes can continue to train while their energy availability improves. If symptoms of an eating disorder are present or there are other health concerns associated, a short break may be necessary. Taking appropriate rest weeks and advancing training slowly is essential during the recovery from a low EA. The good news is that once the energy deficit has been corrected, many athletes have faster times and feel stronger.
Here’s hoping you continue running healthy!
Mountjoy M, Sundgot-Borgen J, Burke L, et al. RED-S CAT. Relative Energy Deficiency in Sport (RED-S) Clinical Assessment Tool (CAT). Br J Sports Med. 2015;49(7):421–423. doi:10.1136/bjsports-2015–094873
Burke LM, Ross ML, Garvican-Lewis LA, et al. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiol. 2017;595(9):2785–2807. doi:10.1113/JP273230