Trained hard on too little fuel? Why it can still matter now

What low energy availability means

Energy availability is what is left from the food you eat after paying for exercise. When that remainder is too small for long enough, the body economizes. It slows or pauses processes it can postpone, such as reproductive hormone production, bone remodeling and some aspects of metabolism.

The International Olympic Committee first described this pattern as Relative Energy Deficiency in Sport in 2014 and updated its consensus in 2023. The update draws on more than 170 newer studies, adds much more information on male athletes, and highlights the role of low carbohydrate availability and the link with mental health.

This can happen without any intent to restrict. High training volumes, busy schedules, poor appetite after hard sessions, or a sport culture that prizes leanness can all leave intake short of need.

Why it gets misread as a hormone problem

In women, the classic sign was missed or stopped periods, sometimes accepted as a normal part of heavy training. In men, there is no equivalent warning light. Under-fueling can lower testosterone and libido quietly, and a blood test may simply show low testosterone with low or normal LH.

On paper, that can look like a pituitary or testicular problem that needs hormone replacement. In reality, the first treatment may be food, rest and a smaller training load. Starting testosterone in that situation can mask the cause and suppress your own production and sperm output.

What it can leave behind

Missed periods matter because low estrogen weakens bone. The National Institute of Arthritis and Musculoskeletal and Skin Diseases lists absent periods before menopause, including from extreme physical activity, as a risk factor for osteoporosis.

• Bone: low estrogen or testosterone during the years when you should have been building peak bone mass can leave lower density and a history of stress fractures.
• Hormones: suppression may resolve when training eases, but it does not always, so it is worth testing rather than assuming.
• Iron: heavy training, low intake and, in women, menstrual losses can leave depleted iron stores.
• Thyroid and metabolism: energy deficit can lower active thyroid hormone, which usually recovers with adequate intake.
• Relationship with food: some athletes carry restrictive habits or anxiety about eating into later life.

Signs worth mentioning to a clinician

• Periods that stopped or became irregular during training, at any age
• Stress fractures, especially more than one or in the hip, pelvis or spine
• Low libido or low morning erections during heavy training phases
• Persistent fatigue, feeling cold, poor recovery or frequent illness
• Rapid weight change or a strong need to control what and how much you eat

What HealifyMD does, and where we stop

A licensed clinician can take a detailed history and order labs that may include sex hormones, LH and FSH, thyroid function, ferritin and iron studies, vitamin D, calcium and a metabolic panel. The goal is to see what is still affected and what has recovered.

If fueling is the likely cause of a low hormone level, we will say so. Hormone therapy may still have a place, for example for a woman in perimenopause with symptoms, but it should come after the energy question is addressed, not instead of it.

HealifyMD does not treat eating disorders and does not set calorie or macro targets. If you are currently restricting, purging, exercising compulsively or feel out of control around food, we will refer you to specialist care, which can include a physician, a registered dietitian and a therapist. Bone density testing, if indicated, happens in person.

When midlife hormone change lands on an old deficit

For women, the menopause transition brings a natural fall in estrogen and a period of faster bone loss. If you start that transition with bone density already lowered by years of missed periods, you have less margin. That makes a conversation about bone health, strength training, calcium, vitamin D and, where appropriate, hormone therapy more pressing.

For men, testosterone tends to drift down gradually with age, weight gain and poor sleep. A former endurance or weight-class athlete with a history of suppression may notice symptoms sooner. The approach is the same: confirm with repeated morning tests, look for reversible causes, then decide on treatment together.

If you are still training hard

Masters athletes are not immune. Training for a marathon or ultra in your 50s while trying to lose weight can recreate the same deficit. Watch for the same signs, and remember that recovery and adequate carbohydrate around training are part of performance, not a weakness.