
What If You're Not Overtrained, You're Just Under-Fuelling? | Dr Trent Stellingwerff
Not overtrained – under-fuelled? Dr Trent Stellingwerff, a lead author of the IOC's REDs clinical assessment tool, explains the signs to watch for and what to do about them. Your easy runs feel hard, you're getting sick more often and your sessions are inconsistent. The usual advice: you're overtrained, back off. Trent thinks that advice is often wrong. In his team's review of the classic overtraining studies, 18 of the 21 that reported nutrition showed an energy or carbohydrate shortfall during the overload period. We cover what energy availability is, why the diagnostic tool doesn't measure it, symptoms you can spot without a lab, how under-fuelling leads to stress fractures, and the one simple equation worth knowing. Free 30-minute call with Joost Want a coach to look at your training and fuelling with you? Book a free 30-minute call at Pace Buddies, online running coaching for recreational runners. We'll talk through your goals, your current training and what's getting in the way. Book your free call · pacebuddies.com Timestamps 00:00 Cold open: a month of not eating 00:30 Intro 01:48 Trent's background 04:00 Why Trent studies under-fuelling 06:30 Pregnancy, breastfeeding and under-fuelling 10:17 Overtraining vs REDs 14:01 A quick word about Pace Buddies 15:42 18 out of 21: what old overtraining studies missed 19:48 What energy availability actually is 22:38 Spring classics: bad race days, fine weekly average 25:31 Why you shouldn't calculate it yourself 28:57 Fasted running: risk and reward 31:52 Race weight and the weight-loss trap 34:30 The symptom list 39:14 How under-fuelling causes stress fractures 42:20 What a runner can actually do 47:20 Why your watch is off by 30% 49:48 Why the diagnostic tool ignores energy intake 51:47 One calorie per kilo per kilometre 55:30 How long does recovery take? 57:28 REDs and eating disorders are not the same 59:19 The study he'd run with unlimited funding The quick version Energy availability = energy intake minus the energy cost of training, corrected for fat-free mass. It is not the same as a calorie deficit: one low day is fine, the pattern is the problem. Rough cost of a run: 1 kcal per kg body weight per km. It dates from the 1960s, was built on a flat treadmill, and falls apart on hills and when walking. Don't try to measure your way out: watch and app calories can be off by about 30%. Watch the symptoms instead. First step: add roughly 300–400 kcal of carbohydrate around training, spread food across the day, and see how you feel after a week. Key papers Overtraining vs REDs: shared pathways, symptoms and complexities (the 18-of-21 review) IOC REDs Clinical Assessment Tool (CAT2): scientific rationale 2023 IOC consensus statement on REDs Low energy availability and bone injury in elite distance runners More of Trent's work on PubMed Find Trent Women's Health and Sport Performance Institute (Boston) · Canadian Sport Institute Pacific (Victoria) Disclosure Trent previously spent six years in R&D at PowerBar (Nestlé Research Center) and has no current commercial interest in anything discussed. This episode touches on eating disorders. REDs and eating disorders overlap but are not the same thing. Nothing here is medical advice or a diagnostic tool. If several of the symptoms sound familiar, see a physician.