Do you exercise to lose fat? You’re not alone – getting lean is a major goal for many people who exercise regularly. But attaining a very low body fat percentage – or a level that is unnaturally low for your genetic make-up – carries big health risks. What most people don’t know is that cutting body fat too rapidly or too severely can wreak havoc with your hormones and result in missed periods (amenorrhoea), reduced fertility and weakened bones.
In a study of regular exercisers, half of the women were found to have subtle menstrual hormone disruption. A third had no periods at all. While the idea of not having the hassle of periods each month may sound appealing, it’s important to understand that this is not healthy! All women of reproductive age, whether an athlete or not, should have regular periods, otherwise there are potential serious health and performance consequences.
It’s all down to a concept called low energy availability (EA). This is the amount of energy available to the body to perform all its essential functions after exercise expenditure is subtracted (i.e. energy intake minus exercise energy expenditure). When this drops too low – either by intentionally or unintentionally restricting energy intake below the level required to meet demand or by increasing your training volume without a corresponding increase in fuel intake – then your body goes into deficit and your periods can stop. In healthy adults, a value of 45 kcal/kg fat-free mass /day equates with energy balance and optimum health.
Amenorrhoea is one of the most obvious external symptoms of Relative Energy Deficiency in Sport (RED-S), defined as a mismatch between your food intake and the energy demands of your body. RED-S developed from the concept of the Female Athlete Triad (relationship between three inter-related components: energy availability, menstrual function and bone health) when it became apparent that low EA had multiple effects on health and performance, and also affects men. In men, it can lead to a drop in testosterone levels.
Researchers believe RED-S is caused by low energy availability but a combination of many lifestyle-related factors are often involved, including stress, poor sleep and rapid weight loss. Doctors sometimes call it lifestyle-induced amenorrhoea or functional hypothalamic amenorrhoea.
Why do periods stop? It has been suggested that it’s an energy-conserving adaptation by the body. When there is insufficient energy available, the body goes into an energy saving mode. The body fat threshold that triggers hormonal disruption and amenorrhoea varies from one person to the next – but is thought to be between 17 and 22%.
The body mechanism is as follows: low energy availability increases cortisol production by the adrenal glands, which disrupts the release of gonadotrophin-releasing hormone (GnRH) from the brain. This, in turn, reduces the production of luteinising hormone (LH), follicle-stimulating hormone (FSH), oestrogen and progesterone, and stops you having periods.
One of the most severe health effects of this hormone disruption is the reduction in bone density and increased risk of early osteoporosis and stress fractures. Oestrogen and progesterone both act directly on bone cells to maintain bone turnover, so when levels drop, the breakdown of old bone exceeds the speed of formation of new bone. The result is loss of bone minerals and a loss of bone density. In men, low testosterone has a similar effect on bones and causes bone mineral loss.
RED-S can severely disrupt your fertility (thus reducing your chances of getting pregnant), slow your metabolic rate, impair immunity, increase fatigue and affect cardiovascular and gut health. Thyroid hormone, growth hormone and IGF-1, are also severely reduced.
RED-S also results in many performance-hindering effects. These include an increased risk of soft tissue injuries, stress fractures, decreased strength and endurance, prolonged healing of injuries and reduced ability to recover from hard training sessions.
However, the good news is that once your body fat level increases over a certain threshold and your training volume is reduced, your hormonal balance, periods and fertility generally return to normal. Studies show that when amenorrhoeic athletes improve their diet and restructure their training programme to improve energy balance, normal menstruation resumes within a few months (depending on the severity of the energy deficiency and the duration of amenorrhoea) and performance improves consistently. This is perhaps the most persuasive reason to seek treatment if you have amenorrhoea.
You should definitely seek advice if you have suffered amenorrhoea for longer than 6 months. An initial consultation with your GP will rule out medical causes of amenorrhoea, such as polycystic ovary syndrome. You should then get a referral to a specialist, such as an endocrinologist or sports medicine doctor.
- Treatment will centre on increasing energy availability and restoring ‘normal’ body weight and body fat. This usually means increasing your food intake (usually by 300 – 600 kcal a day) and you may be advised to reduce your training frequency, volume and intensity, incorporate periodisation to your current programme or include more recovery.
- As well as energy intake, focus on improving the nutritional quality of your food intake to ensure you’re meeting your macronutrient and micronutrient needs. Consult a registered dietitian (RD) or registered nutritionist (RNutr) if you would like more detailed advice.
- Avoid any diet that eliminates entire food groups or centres around a set of strict rules – restrictive eating plans are likely to be deficient in nutrients that you need for proper endocrine functioning and may lead to unhealthy obsession with food. If you suspect a food allergy or intolerance, seek a medical diagnosis and professional guidance. Do not self-diagnose or use high street or home test kits.
- Focus on your recovery nutrition – replenishing energy and consuming sufficient protein after training sessions are key for the prevention and treatment of RED-S.
If you enjoyed this post and want to find out more about sports nutrition, then check out the new edition of The Complete Guide to Sports Nutrition , the definitive practical handbook for anyone wanting a performance advantage. It’s the 8th edition (the 1st edition came out in 1993!) and it has been fully updated and revised to bring together the latest research and information on sport and exercise nutrition. It covers topics such as
- Maximizing endurance, strength and performance
- Carbohydrate, protein and fat requirements
- Sports supplements
- Improving body composition
- Eating plans to cut body fat, gain muscle and prepare for competition
- Hydration and fluid intake