Case Study 2 — The Wrong Person: Devi, Fasting, and Low Energy Availability

Devi Raghunathan is an illustrative composite carried through this book — a competitive distance runner first seen in Chapter 14 with ferritin 11 and a falling haemoglobin trend. ⚠️ RED-S, low energy availability and the clinical features described are real; the person is constructed.

Setup

Chapter 14 left Devi mid-correction. Ferritin 11 µg/L, haemoglobin trending 13.1 → 12.8 → 12.6, iron started, training adjusted, and — the finding that mattered more than the iron — ⚠️ energy availability of about 31.8 kcal/kg fat-free mass per day.

She came back nine months later. The iron had worked. Something else hadn't.

"I've been doing 16:8. Everyone in my club does it. It's supposed to be good for endurance — you get fat-adapted."

She had been doing it for five months.

Why this is the wrong intervention for this person

Energy availability is the quantity that matters here, and it's worth restating because it's not intuitive:

Energy availability = (energy intake − exercise energy expenditure) ÷ fat-free mass

⚠️ It is the energy left over for everything your body does that isn't the training session — hormones, bone turnover, immune function, menstrual cycling, repair.

Reference figures commonly cited: around 45 kcal/kg FFM/day for optimal function; below about 30 is where clinical consequences are consistently observed.

Devi was at 31.8 nine months ago. She had since added a protocol that removes eating opportunities.

⚠️ She had moved from borderline to clearly deficient, while doing everything her club recommended.

What was actually happening

The presenting complaints were not what she came in for. She came in about the iron.

The last row is the one I'd underline. ⚠️ Athletes present when performance drops, and performance is one of the last things to go. By the time the times slow, the bone, the hormones and the immune system have been running a deficit for months.

Why the protocol was especially badly matched

Four reasons, and they compound.

1. ⚠️ Training is not optional and neither is fuelling around it. Devi ran at 6:15am. On 16:8 with a noon start, she ran fasted and then didn't eat for six more hours. The single most important window for glycogen resynthesis and protein delivery — the hours after a hard session — was inside her fasting window.

2. She physically could not fit the calories in. ⚠️ An athlete needing 3,000+ kcal in an eight-hour window is a mechanical problem, not a willpower one. Large meals in a compressed window cause GI distress, particularly around training. She was under-eating because the container was too small.

3. Protein distribution collapsed. Chapter 8: muscle protein synthesis responds to distributed doses. ⚠️ Three eating occasions in an athlete with high turnover and elevated requirements is not enough, and her total protein had fallen to around 1.1 g/kg — well below the range for a heavily-training endurance athlete.

4. ⚠️ And "fat-adapted" is a real phenomenon being asked to do a job it can't do. Fasted training does increase fat oxidation (Chapter 6 §6.4) — this is genuine. But her races are run at intensities where glycogen is the limiting substrate, and increased fat oxidation at low intensity does not raise the ceiling at high intensity. ⚠️ She had adapted to burn more fat during exactly the sessions where it didn't matter, at the cost of fuelling the ones where it did.

💡 Aha moment. ⚠️ Every argument for intermittent fasting in the general population inverts for an athlete in heavy training.

§21.10's case is that IF helps people eat less. ⚠️ Devi's problem was that she was already eating too little.

The intervention did exactly what it does. It was aimed at the wrong person — which is Chapter 18's fourth slot, in whom, and it is the slot that gets left empty most often and costs most when it does.

What changed

⚠️ The fasting stopped. That was not a negotiation.

Four months later: periods regular, no illness since, and — the part she cared about — ⚠️ her times came back and then went past where they'd been.

She said: "I ran faster eating more. That still doesn't make sense to me."

⚠️ It makes complete sense and it is the hardest thing to convey in endurance sport.

The club

The uncomfortable part, and the reason this is a case study rather than a note.

⚠️ Devi didn't invent this. Her whole training group was doing it, and several of them were young women in heavy training with the same risk profile.

The protocol had spread through the club as performance advice, carrying the "fat-adapted" justification, from people with no ill intent and no idea about energy availability.

⚠️ And in a sport where thinness is widely believed to improve performance, a socially endorsed protocol that reduces intake is a serious problem — not because everyone doing it has an eating disorder, but because it removes the friction that would otherwise make under-eating noticeable.

§21.12's eating-disorder subsection applies here at full strength. ⚠️ "I'm doing 16:8" is a sentence that makes not eating look like training.

Analysis

1. ⚠️ EA fell from 31.8 to ~26 while she followed advice she'd been given as performance guidance.

2. The post-session window was inside the fasting window — the single worst placement available for an athlete training in the morning.

3. It was a container problem, not a willpower problem. ⚠️ 3,000+ kcal does not comfortably fit in eight hours around training.

4. Performance declined last. ⚠️ Bone, hormones and immune function had been in deficit for months before the times moved — which is why "my times are fine" is not reassurance.

5. "Fat-adapted" is real and was irrelevant. ⚠️ Increased fat oxidation at low intensity does not raise the glycogen-limited ceiling at race intensity.

6. ⚠️ Training was reduced as well as intake raised, because energy availability has two terms and the food side alone was too slow.

7. And the club transmitted it socially, in a sport with a pre-existing thinness culture. ⚠️ The protocol didn't cause that culture; it gave it a vocabulary.

Discussion Questions

1. ⚠️ Every argument for IF inverts for an athlete in heavy training. Name two other populations where a mainstream dietary recommendation inverts, and say what the general rule is.

2. Performance declines last. ⚠️ What should endurance athletes monitor instead, and how often? Design a four-item self-check that a club could actually use.

3. Devi's club spread the protocol as performance advice. ⚠️ Who should have intervened? What would you say to a coach who's been recommending it for two years?

4. ⚠️ "I'm doing 16:8" makes not eating look like training. Is that an argument against the protocol, or against the culture? Can you separate them?

5. She ran faster eating more. ⚠️ Why is that so hard to convey? What would change a performance-focused athlete's mind — and does that answer worry you?

6. Training was cut for six weeks. ⚠️ That's the intervention athletes resist most. Make the case for it in three sentences, to someone with a race in ten weeks.

Your Turn

⚠️ This section is for anyone who trains more than about five hours a week, and for anyone who coaches someone who does.

Step 1 — Estimate your energy availability. Roughly is fine.

(Intake − exercise energy expenditure) ÷ fat-free mass (kg) = ____ kcal/kg FFM/day

⚠️ Reference: ~45 for optimal function; below ~30 is where consequences are consistently observed. Estimates are crude — Chapter 2's measurement problems apply — so treat this as a flag rather than a number.

Step 2 — The RED-S checklist. ⚠️ Tick anything true in the last six months:

• [ ] Menstrual irregularity or absence (⚠️ and note: this is not a normal consequence of training)
• [ ] A bone stress injury
• [ ] Recurrent illness or slow recovery from it
• [ ] Persistent fatigue, or "dead legs" on second sessions
• [ ] Poor sleep
• [ ] Low ferritin or haemoglobin (Chapter 14)
• [ ] Reduced libido
• [ ] Frequent minor injuries
• [ ] Performance plateau or decline

⚠️ Two or more, with training load high: this is a conversation with a sports dietitian or physician, not a protocol adjustment.

Step 3 — The window question.

When is your hardest session, and is the hour after it inside your eating window? ____

⚠️ If no, that's the finding, and it doesn't require any of the rest of this.

Step 4 — And the honest one:

⚠️ "Am I doing this to perform better, or to be lighter?"

If it's the second, say so — to yourself first, and then to someone. In endurance sport those two answers get deliberately blurred, and the blurring is where the harm lives. Chapter 34.