If you are training hard and eating less, do one quick check this week: write down what you eat and how much you train for seven days, then ask whether your fuel plausibly covers your workload. If you are tired, stalling, or sleeping badly while that gap is large, bring the log to a sports-minded registered dietitian or your clinician.
The gap has a name. Relative Energy Deficiency in Sport (REDs) is a syndrome of health and performance problems in female and male athletes who live with low energy availability, which means eating too little for the energy their exercise burns. The International Olympic Committee’s 2023 consensus statement updated the model and added a clinical assessment tool for detecting it.[1]
Why it is not just an elite-athlete problem
The consensus statement was written for athletes, and I did not find evidence in the sources I checked that it applies the same way to recreational exercisers over 40. What it does show is that the idea is wider than it used to be. Since the 2018 version, more than 170 original research papers have appeared, including more data in males, evidence for a growing role of low carbohydrate availability, and further links with mental health.[1] A hard new training plan layered on a diet or a very low appetite is a plausible way to end up on the wrong side of the line, which is why a one-week check is worth doing.
A threshold, and its limits
Energy availability is what is left of your food energy after exercise: (energy eaten minus energy spent exercising) divided by your fat-free mass (everything that is not fat). In a classic lab study, 29 young, regularly menstruating women spent five days with energy availability set at 45, 30, 20, or 10 kcal per kg of lean body mass per day. Hormone pulses that drive the menstrual cycle were unaffected at 30, and below 30 they were disrupted.[2]
That is why you often see 30 kcal per kg of lean mass cited as a floor. It is not a rule for body weight. As an illustration only: with 60 kg of fat-free mass, eating 2,400 kcal and burning 600 kcal in exercise gives (2,400 minus 600) / 60 = 30 kcal per kg.
Treat that number as a prompt, not a diagnosis. It came from one short study of young women and one hormone outcome. It has not been shown to be the right line for men, for people over 40, or for you. You also need a measure of fat-free mass, such as a DEXA scan, which most people do not have, and food logs are imprecise.
What to do
- Log seven days. Food, workouts, sleep, mood, and how your training numbers move. A phone note is enough.
- Look for the pattern, not the number. Several weeks of stalled lifts, poor sleep, low mood, or a drop in motivation while you are eating very little is a reason to eat more and ask for help.
- Match fuel to the plan. When you raise training volume, raise food with it. Do not start a hard program and a deficit in the same week.
- Include carbohydrate around hard sessions. The consensus flags low carbohydrate availability as a growing area, so do not drop it to zero while training hard.
- Ask for a professional. A sports-minded registered dietitian can estimate your needs and check your numbers. If you have missed periods, repeated injuries, or persistent low mood, tell your clinician as well.
- Check on medication. If you take an appetite-suppressing medication such as a GLP-1, ask your prescriber how much you should be eating while you train. Do not change the dose on your own.
What this does not tell you
- The consensus statement is expert guidance built on available research, not a randomized trial, and I could only verify its abstract, not its full text.
- The 30 kcal per kg figure comes from a five-day study in 29 young women and is not a universal cutoff.
- I found no primary data that tests whether recreational exercisers or GLP-1 users develop REDs at a given intake, so treat the GLP-1 point above as a precaution, not a finding.
The takeaway
Fuel is part of the training plan. A seven-day log takes five minutes a day and tells you whether your intake plausibly covers your workload. If it does not, change the food before you change the workout, and get a dietitian involved.
References
↑︎ Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023. Finding as used: REDs is a syndrome of health and performance outcomes in female and male athletes exposed to low energy availability; more than 170 original research papers since 2018, including more data in males, the growing role of low carbohydrate availability, and the interplay with mental health; a REDs Clinical Assessment Tool-Version 2 was introduced. DOI: https://doi.org/10.1136/bjsports-2023-106994
↑︎ Loucks AB, Thuma JR. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab. 2003. Finding as used: in 29 young women over 5 days, LH pulsatility was unaffected at 30 kcal/kg lean body mass per day and disrupted below it. DOI: https://doi.org/10.1210/jc.2002-020369
Kurt Greiner
Kurt is a digital strategist and IT professional blending emerging technology with practical application, exploring how individuals can leverage modern tools to navigate the second half of life with purpose.
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