Fitness, muscle and fasted training
Read the training studies closely: separate fuel use, muscle size, strength, food intake and recovery before drawing a conclusion.
Fasting Free educational synthesis. Independent clinical review of this site content has not been completed.
THE QUESTION BEHIND THE HEADLINE
Can fasting fit with training—and what would count as evidence that it helps?
Some studied eating schedules coexist with training gains. That is a narrower claim than saying fasting improves muscle growth, workout quality or fat loss. The answer depends on the comparison, the food actually consumed and the outcome measured.
Start with a precise question. “Does fasting work for fitness?” combines several different goals: changing body composition, adding muscle, lifting a heavier weight, completing more work, and recovering between sessions. A useful paper can answer one of these questions without settling the others. Keep the intended outcome visible while reading the methods and results.
This guide follows a chain from the research question to the comparison, the measurement and the uncertainty. The linked source cards supply study details, including population, duration, access and disclosures. The claims below explain how to use those details. A protocol describes what investigators tested; it does not automatically become a suitable routine for the reader.
Give each result the scope it earned. Ask which participants were included, how many remained, what both groups did, and whether the investigators measured the outcome you care about. Then read the limitation before choosing the headline. A qualified conclusion is still useful: it tells us what the study adds and which next experiment would resolve the remaining question.
BEFORE COMPARING RESULTS
Get the terms right.
- Time-restricted eating
A daily window for caloric intake. It does not tell you whether exercise happened before or after food.
Read the evidence2- Fasted training
Exercise undertaken without a preceding meal over the specified interval. Read that interval; an overnight fast is not interchangeable with several days without food.
Read the evidence3- Fat oxidation
Using fat for fuel over a measured period. A fuel-use result and a change in stored body fat answer different questions.
- Fat-free mass and hypertrophy
Fat-free mass includes tissues and water beyond skeletal muscle. Hypertrophy means muscle enlargement; check whether size was measured directly.
- Strength and training volume
Maximal strength tests the heaviest successful effort. Volume records accumulated work; studies may count repetitions or use load and repetitions together.
- Energy availability
Energy remaining for body functions after exercise demands. The IOC distinguishes problematic under-fueling from a brief eating interval alone.
Read the evidence8
CLAIM BY CLAIM
What can the research support?
Do eating-window studies prove that fasted workouts build muscle?
No. First establish when participants trained relative to their meals. A trial of meal scheduling may not test fasted exercise at all.
Tinsley’s women’s trial deliberately scheduled fed workouts. Moro’s earlier study examined a daily eating pattern alongside standardized training. These are useful comparisons, but neither justifies replacing the research question with “Is skipping the pre-workout meal better?”
Draw a simple timeline when reading the paper: meals, training, supplements and testing. If one group changes its eating window but both groups train after eating, the experiment isolates a different decision from moving the workout before breakfast. If several elements change together, the package can be evaluated, but attributing its effect to a single element requires another comparison.
Also distinguish preservation from growth. A study designed around maintaining an existing outcome need not demonstrate its maximum achievable improvement. To claim an advantage, look for a credible difference against the comparator, rather than celebrating improvement within one group. Ask whether the same training and support could explain improvement in both.
Keep this boundary in view
Do not transfer a result across different workout feeding states, training goals or fasting durations without saying that this is an extrapolation.
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Does an overnight fast necessarily prevent training adaptations?
The direct comparison does not support that absolute claim. It also does not establish that fasted training is preferable for every person or workout.
Vieira’s trial compared fasted and fed resistance exercise. Its results support the possibility of adaptation under both studied conditions. Read the participant flow alongside the outcomes: the people represented in the final analysis are not automatically everyone who began.
Suppose two groups improve and their difference is statistically uncertain. There are several possible explanations: their true responses may be close, a difference may be smaller than the study could reliably identify, or the measurements may be too variable. “No clear difference detected” communicates that uncertainty. “Proven identical” requires a different argument and, usually, an explicit equivalence design.
The training demand also belongs in the conclusion. Before applying a result to a different program, ask whether the frequency, total work, participant experience and opportunity to eat after exercise resemble the experiment. These questions do not invalidate the trial. They define the circumstances to which it most directly contributes evidence.
Keep this boundary in view
A short supervised comparison cannot establish lifelong safety, effects of prolonged fasting, or results in every sport and medical population.
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If strength improves, has performance been preserved completely?
An improved maximum lift settles only the outcome that was tested. Muscle size, repeated work and the experience of training deserve their own results.
Blake’s study is useful because its outcomes did not all move together. Read the training-volume result alongside the body-composition result, and notice that direct muscle imaging was unavailable. Avoid replacing all of these measurements with one broad label such as “better fitness.”
Imagine a hypothetical intervention that raises a person’s best single effort while making the later sets harder to complete. The first result would matter for a maximum-strength goal; the second would matter when evaluating the training program. Neither result cancels the other. A clear interpretation names both and explains which question each addresses.
Look carefully at the test itself. Was performance assessed under the same feeding conditions in both groups? Was the reported number a single exercise, an average across exercises or accumulated work? Were several analyses performed? A result that changes with the analysis deserves a less decisive headline. This is especially important when a paper offers many outcomes from a small sample.
Keep this boundary in view
Neither a maximum-lift test nor a body-composition estimate establishes repeated-sprint ability, competition performance or long-term recovery.
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Does burning more fat during exercise guarantee greater fat loss?
No. A short observation of fuel use cannot substitute for measuring body composition over the period in question.
Iwayama measured fuel use in a metabolic chamber. Schoenfeld tested changes in body composition during a training intervention. Read these as complementary questions rather than treating their different findings as a contradiction.
Keep the unit and time span attached to a result. Energy derived from fat during a session, or over a day, is not the same measurement as kilograms of body fat lost over weeks. A persuasive mechanism helps explain why an outcome might occur. It cannot supply a missing measurement of that outcome.
To evaluate a fat-loss claim, ask whether the comparison followed participants long enough to observe the proposed change, measured that change, and examined food intake and exercise in both groups. Then examine precision: an inconclusive small trial does not prove a universal absence of effect. The defensible conclusion can be that an advertised advantage has not been demonstrated by the evidence being cited.
Keep this boundary in view
A tightly controlled fuel-use experiment and a short free-living training trial each answer a limited question; neither alone settles long-term effectiveness.
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What should “matched calories and protein” mean to a reader?
Check what was matched: the advice, the foods supplied, or the intake actually recorded. Those are different levels of control.
Morton’s review gives protein and resistance training their own evidence base. Its findings are not a direct test of fasting, and its included studies did not examine intentional energy deficits. Using that review to settle every fasting-related nutrition question would extend it beyond its design.
A useful reading sequence is prescription, adherence, then measurement. First identify what researchers asked participants to consume. Next check whether they followed it. Finally ask how the investigators know: provided meals, weighed records, an app or recall. Equal instructions can coexist with unequal intake, while a nonsignificant intake comparison in a small sample is not proof of exact matching.
Treat a fitted dose-response curve with the same discipline. Its estimate summarizes particular studies and assumptions; it does not reveal a precise personal cutoff. The practical educational task is to identify what role nutrition played in the comparison, not to extract a universal gram target from a graph. A strong explanation says what was controlled and what remains uncertain.
Keep this boundary in view
Supplement evidence does not make supplements compulsory or establish a suitable protein, calorie or meal prescription for an individual.
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What does recovery add to the discussion?
A schedule must be evaluated alongside health and recovery, not just the completion of a fast or a change on the scale.
The IOC consensus addresses problematic low energy availability in athletes of both sexes. Its concerns include reproductive and musculoskeletal health as well as performance. It describes a clinical syndrome, not a diagnosis that can be calculated from the length of an eating window.
For education, keep three questions separate: Did the measured performance change? Could participants sustain the intervention? Were concerning symptoms or health outcomes assessed? A paper can answer the first question well while providing little information about the others. Read adverse-event reporting and reasons for withdrawal as part of the evidence, rather than treating them as optional details.
Persistent fatigue, menstrual disruption or recurrent injury deserves assessment in context; these signs do not identify a single cause. A small trial’s average result cannot determine whether a particular person is adequately fueled. A useful conversation with a qualified clinician or sports dietitian brings together the training demand, eating pattern, symptoms and relevant history, rather than relying on a timer alone.
Keep this boundary in view
Short-term tolerance is not proof of long-term safety. The consensus is not a self-diagnosis tool or a fasting protocol.
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COMPARE THE METHODS
Different designs answer different questions.
A controlled feeding trial, a training study, and clinical guidance are different kinds of evidence. Start with the design before comparing their conclusions.
| Source and design | People and duration | What was compared |
|---|---|---|
| 1. An eating window alongside resistance trainingRandomized controlled trial | Men with resistance-training experience34 randomized8 weeks | Three meals within 8 hours versus three meals spread across the day, alongside resistance training. Energy and macronutrients were intended to match and assessed using food diaries and interviews; this was not a controlled feeding study. |
| 2. Eating windows and resistance training in womenRandomized controlled trial | Resistance-trained women aged 18–3040 randomized; 24 in the per-protocol analysis8 weeks | Eight-hour eating windows, with or without HMB, versus a longer eating day; supervised training and whey protein in every group. |
| 3. Resistance training before or after breakfastRandomized controlled trial | Adults aged 20–40 without regular resistance training37 recruited; 28 completed, including 22 women12 weeks | Twice-weekly training after an overnight fast or a carbohydrate-rich meal, with comparable dietary guidance. |
| 4. Eating windows during a muscle-building studySmall randomized controlled trial | Well-trained adults: 10 men and 7 women17 participants8 weeks | TRE with fasted workouts versus fed training; both prescribed energy surplus and matched macronutrients. |
| 5. Protein and the response to resistance trainingSystematic review and meta-analysis of randomized trials | Healthy adults undertaking resistance training49 trials; 1,863 participantsTraining interventions lasting at least 6 weeks | Protein supplementation versus control during resistance training. |
| 6. Measuring fuel use over one dayRandomized repeated-measures laboratory experiment | Healthy young men10 participantsFour separate 24-hour calorimetry conditions | Cycling before breakfast, after lunch or after dinner, and a sedentary condition; energy balance controlled. |
| 7. Fasted cardio and measured fat lossSmall randomized controlled trial | Healthy young women20 randomized4 weeks | Equal aerobic training with a shake before or after exercise; both groups received calorie-deficit guidance. |
| 8. Energy availability, recovery and athlete healthExpert consensus informed by athlete research | Female and male athletes | Consensus synthesis, not a randomized comparison of fasting schedules. |
On a narrow screen, scroll the comparison to see every column.
Compare three core papers in the source libraryTHE PAPERS, WITH A READING PLAN
Read the originals.
Each numbered source connects to the claims above. Open its findings, methods, and disclosures, or go directly to the publication. Access notes describe what we could review.
View all references
These references credit the original publications. The explanations and reading notes in this guide are by Fasting Free.
Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males
Moro et al. · Journal of Translational Medicine
An early reference point for the literature.
Read for: How maintenance goals differ from claims about maximizing growth.
Full text and methods verified.
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Findings, methods, and disclosures
- Design and scope
- Randomized controlled trial. Men with resistance-training experience; 34 randomized.
- Duration
- 8 weeks
- Comparison
- Three meals within 8 hours versus three meals spread across the day, alongside resistance training. Energy and macronutrients were intended to match and assessed using food diaries and interviews; this was not a controlled feeding study.
- What was measured
- DXA fat mass and fat-free mass, anthropometric arm/thigh muscle-area estimates, and bench/leg-press maximal strength.
- Finding
- Fat mass decreased more with time restriction. Fat-free mass and maximal strength were maintained in both groups.
- Limits
- A small, short study in trained men does not establish long-term muscle gain, recovery, or benefits for other populations. Intake differences may have remained despite intended matching. Maintaining measured lean mass is different from proving superior hypertrophy.
- Design and scope
- Randomized controlled trial. Men with resistance-training experience; 34 randomized.
- Duration
- 8 weeks
- Comparison
- Three meals within 8 hours versus three meals spread across the day, alongside resistance training. Energy and macronutrients were intended to match and assessed using food diaries and interviews; this was not a controlled feeding study.
- What was measured
- DXA fat mass and fat-free mass, anthropometric arm/thigh muscle-area estimates, and bench/leg-press maximal strength.
- Finding
- Fat mass decreased more with time restriction. Fat-free mass and maximal strength were maintained in both groups.
- Limits
- A small, short study in trained men does not establish long-term muscle gain, recovery, or benefits for other populations. Intake differences may have remained despite intended matching. Maintaining measured lean mass is different from proving superior hypertrophy.
Original source: https://pmc.ncbi.nlm.nih.gov/articles/PMC5064803/
DOI: https://doi.org/10.1186/s12967-016-1044-0
Time-restricted feeding plus resistance training in active females: a randomized trial
Tinsley et al. · The American Journal of Clinical Nutrition
A clear example of why training timing matters.
Read for: The meal-and-workout timeline and intention-to-treat versus per-protocol results.
Full text and methods reviewed.
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Findings, methods, and disclosures
- Design and scope
- Randomized controlled trial. Resistance-trained women aged 18–30; 40 randomized; 24 in the per-protocol analysis.
- Duration
- 8 weeks
- Comparison
- Eight-hour eating windows, with or without HMB, versus a longer eating day; supervised training and whey protein in every group.
- What was measured
- Four-component body composition, ultrasound muscle thickness, strength and endurance.
- Finding
- Muscle and performance improved across groups. A fat-mass difference appeared only in the per-protocol analysis.
- Limits
- Workouts were deliberately fed. Reported intake was similar, not laboratory-controlled; incomplete follow-up limits certainty.
- Funding and disclosures
- MTI Biotech and Texas Tech support; MTI and Dymatize products donated. Authors reported no relevant conflicts.
- Design and scope
- Randomized controlled trial. Resistance-trained women aged 18–30; 40 randomized; 24 in the per-protocol analysis.
- Duration
- 8 weeks
- Comparison
- Eight-hour eating windows, with or without HMB, versus a longer eating day; supervised training and whey protein in every group.
- What was measured
- Four-component body composition, ultrasound muscle thickness, strength and endurance.
- Finding
- Muscle and performance improved across groups. A fat-mass difference appeared only in the per-protocol analysis.
- Limits
- Workouts were deliberately fed. Reported intake was similar, not laboratory-controlled; incomplete follow-up limits certainty.
- Funding and disclosures
- MTI Biotech and Texas Tech support; MTI and Dymatize products donated. Authors reported no relevant conflicts.
Original source: https://pmc.ncbi.nlm.nih.gov/articles/PMC6735806/
DOI: https://doi.org/10.1093/ajcn/nqz126
Impact of Overnight Fasted State Versus Fed State on Adaptations to Resistance Training: A Randomized Clinical Trial
Vieira et al. · International Journal of Sport Nutrition and Exercise Metabolism
A direct comparison of workout feeding states.
Read for: Participant flow, dietary monitoring and the outcomes named in the conclusion.
Full article reviewed in an author-uploaded copy; publisher fetch blocked.
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Findings, methods, and disclosures
- Design and scope
- Randomized controlled trial. Adults aged 20–40 without regular resistance training; 37 recruited; 28 completed, including 22 women.
- Duration
- 12 weeks
- Comparison
- Twice-weekly training after an overnight fast or a carbohydrate-rich meal, with comparable dietary guidance.
- What was measured
- DXA, quadriceps ultrasound, maximal strength and muscle power.
- Finding
- Both groups improved muscle thickness and strength without clear between-group differences in those outcomes.
- Limits
- Completer results, modest training frequency and self-reported diets. Some fasted participants reported dizziness, tiredness or nausea.
- Funding and disclosures
- Brazilian public research support: CAPES, CNPq and FAPERGS.
- Design and scope
- Randomized controlled trial. Adults aged 20–40 without regular resistance training; 37 recruited; 28 completed, including 22 women.
- Duration
- 12 weeks
- Comparison
- Twice-weekly training after an overnight fast or a carbohydrate-rich meal, with comparable dietary guidance.
- What was measured
- DXA, quadriceps ultrasound, maximal strength and muscle power.
- Finding
- Both groups improved muscle thickness and strength without clear between-group differences in those outcomes.
- Limits
- Completer results, modest training frequency and self-reported diets. Some fasted participants reported dizziness, tiredness or nausea.
- Funding and disclosures
- Brazilian public research support: CAPES, CNPq and FAPERGS.
Original source: https://pubmed.ncbi.nlm.nih.gov/40335157/
DOI: https://doi.org/10.1123/ijsnem.2024-0215
Hypercaloric 16:8 time-restricted eating during 8 weeks of resistance exercise in well-trained men and women
Blake et al. · Journal of the International Society of Sports Nutrition
A useful exercise in reading several outcomes together.
Read for: Whether the headline still fits after inspecting each result separately.
Full article reviewed through a public copy; publisher access intermittent.
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Findings, methods, and disclosures
- Design and scope
- Small randomized controlled trial. Well-trained adults: 10 men and 7 women; 17 participants.
- Duration
- 8 weeks
- Comparison
- TRE with fasted workouts versus fed training; both prescribed energy surplus and matched macronutrients.
- What was measured
- Three-component body composition, maximal strength, endurance, repetitions and energy ratings.
- Finding
- Both groups gained fat-free mass. TRE completed fewer repetitions and gained less fat; squat findings varied by analysis.
- Limits
- Small free-living sample; no direct muscle imaging. Eating windows and workout feeding changed together.
- Funding and disclosures
- International Scientific Research Foundation for Fitness and Nutrition funding; Legion donated whey. Tinsley disclosed an HMB/fasting patent.
- Design and scope
- Small randomized controlled trial. Well-trained adults: 10 men and 7 women; 17 participants.
- Duration
- 8 weeks
- Comparison
- TRE with fasted workouts versus fed training; both prescribed energy surplus and matched macronutrients.
- What was measured
- Three-component body composition, maximal strength, endurance, repetitions and energy ratings.
- Finding
- Both groups gained fat-free mass. TRE completed fewer repetitions and gained less fat; squat findings varied by analysis.
- Limits
- Small free-living sample; no direct muscle imaging. Eating windows and workout feeding changed together.
- Funding and disclosures
- International Scientific Research Foundation for Fitness and Nutrition funding; Legion donated whey. Tinsley disclosed an HMB/fasting patent.
Original source: https://pmc.ncbi.nlm.nih.gov/articles/PMC12006946/
DOI: https://doi.org/10.1080/15502783.2025.2492184
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults
Morton et al. · British Journal of Sports Medicine
A chance to practice reading a meta-analysis.
Read for: Eligibility criteria and the uncertainty around a fitted threshold.
Full text and methods reviewed.
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Findings, methods, and disclosures
- Design and scope
- Systematic review and meta-analysis of randomized trials. Healthy adults undertaking resistance training; 49 trials; 1,863 participants.
- Duration
- Training interventions lasting at least 6 weeks
- Evidence searched through
- Search boundary
- The search strategy reports January 2017 without a specific day.
- Comparison
- Protein supplementation versus control during resistance training.
- What was measured
- Fat-free mass, muscle-size measurements and maximal strength.
- Finding
- Additional protein modestly improved average gains alongside training.
- Limits
- Included studies met or exceeded energy requirements. This is not a fasting or weight-loss review; its dose-response estimate is uncertain.
- Funding and disclosures
- Phillips disclosed National Dairy Council support; that organization supported some included trials.
- Design and scope
- Systematic review and meta-analysis of randomized trials. Healthy adults undertaking resistance training; 49 trials; 1,863 participants.
- Duration
- Training interventions lasting at least 6 weeks
- Evidence searched through
- Search boundary
- The search strategy reports January 2017 without a specific day.
- Comparison
- Protein supplementation versus control during resistance training.
- What was measured
- Fat-free mass, muscle-size measurements and maximal strength.
- Finding
- Additional protein modestly improved average gains alongside training.
- Limits
- Included studies met or exceeded energy requirements. This is not a fasting or weight-loss review; its dose-response estimate is uncertain.
- Funding and disclosures
- Phillips disclosed National Dairy Council support; that organization supported some included trials.
Original source: https://pmc.ncbi.nlm.nih.gov/articles/PMC5867436/
DOI: https://doi.org/10.1136/bjsports-2017-097608
Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast
Iwayama et al. · EBioMedicine
An example of a tightly defined mechanism question.
Read for: The measurement, its unit and its observation period.
Full text and methods reviewed.
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Findings, methods, and disclosures
- Design and scope
- Randomized repeated-measures laboratory experiment. Healthy young men; 10 participants.
- Duration
- Four separate 24-hour calorimetry conditions
- Comparison
- Cycling before breakfast, after lunch or after dinner, and a sedentary condition; energy balance controlled.
- What was measured
- Measured energy expenditure and substrate oxidation.
- Finding
- Pre-breakfast exercise increased 24-hour fat oxidation in this experiment.
- Limits
- Meal state and clock time differed together. This measured fuel use, not a long-term change in body fat.
- Funding and disclosures
- Japanese public research grants; authors reported funders had no role in the research or manuscript.
- Design and scope
- Randomized repeated-measures laboratory experiment. Healthy young men; 10 participants.
- Duration
- Four separate 24-hour calorimetry conditions
- Comparison
- Cycling before breakfast, after lunch or after dinner, and a sedentary condition; energy balance controlled.
- What was measured
- Measured energy expenditure and substrate oxidation.
- Finding
- Pre-breakfast exercise increased 24-hour fat oxidation in this experiment.
- Limits
- Meal state and clock time differed together. This measured fuel use, not a long-term change in body fat.
- Funding and disclosures
- Japanese public research grants; authors reported funders had no role in the research or manuscript.
Original source: https://pmc.ncbi.nlm.nih.gov/articles/PMC4703705/
DOI: https://doi.org/10.1016/j.ebiom.2015.10.029
Body composition changes associated with fasted versus non-fasted aerobic exercise
Schoenfeld et al. · Journal of the International Society of Sports Nutrition
A companion to the mechanism experiment.
Read for: The distinction between an uncertain comparison and established equivalence.
Full text and methods reviewed.
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Findings, methods, and disclosures
- Design and scope
- Small randomized controlled trial. Healthy young women; 20 randomized.
- Duration
- 4 weeks
- Comparison
- Equal aerobic training with a shake before or after exercise; both groups received calorie-deficit guidance.
- What was measured
- Body weight, fat mass and fat-free mass.
- Finding
- Both groups lost weight and fat; the study did not detect a difference between groups.
- Limits
- Short follow-up, small groups and self-reported intake cannot establish equivalence or exclude smaller differences.
- Funding and disclosures
- Dymatize supplied shakes. Authors declared no competing interests.
- Design and scope
- Small randomized controlled trial. Healthy young women; 20 randomized.
- Duration
- 4 weeks
- Comparison
- Equal aerobic training with a shake before or after exercise; both groups received calorie-deficit guidance.
- What was measured
- Body weight, fat mass and fat-free mass.
- Finding
- Both groups lost weight and fat; the study did not detect a difference between groups.
- Limits
- Short follow-up, small groups and self-reported intake cannot establish equivalence or exclude smaller differences.
- Funding and disclosures
- Dymatize supplied shakes. Authors declared no competing interests.
Original source: https://link.springer.com/article/10.1186/s12970-014-0054-7
DOI: https://doi.org/10.1186/s12970-014-0054-7
2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs)
Mountjoy et al. · British Journal of Sports Medicine
The health context around performance discussions.
Read for: Definitions, clinical limits and the linked correction.
Original full-text sections and correction reviewed; direct publisher access intermittent.
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Findings, methods, and disclosures
- Design and scope
- Expert consensus informed by athlete research. Female and male athletes.
- Comparison
- Consensus synthesis, not a randomized comparison of fasting schedules.
- What was measured
- Health and performance consequences of problematic low energy availability.
- Finding
- Prolonged or severe under-fueling can impair multiple body systems and performance.
- Limits
- Clinical assessment requires context and exclusion of other causes. Neither a fasting duration nor one symptom diagnoses REDs.
- Funding and disclosures
- IOC-supported consensus; author editorial and institutional relationships are listed in the article.
- Design and scope
- Expert consensus informed by athlete research. Female and male athletes.
- Comparison
- Consensus synthesis, not a randomized comparison of fasting schedules.
- What was measured
- Health and performance consequences of problematic low energy availability.
- Finding
- Prolonged or severe under-fueling can impair multiple body systems and performance.
- Limits
- Clinical assessment requires context and exclusion of other causes. Neither a fasting duration nor one symptom diagnoses REDs.
- Funding and disclosures
- IOC-supported consensus; author editorial and institutional relationships are listed in the article.
Original source: https://bjsm.bmj.com/content/57/17/1073
DOI: https://doi.org/10.1136/bjsports-2023-106994
PUT THE EVIDENCE TO USE
Practice asking the better question.
Hypothetical: a “fat-burning” headline
A fictional article promotes a morning routine because a laboratory test found a greater proportion of energy came from fat. Its illustration shows a dramatic body transformation, but the study only observed a brief test period. A friend asks whether the photograph represents the result that researchers measured.
- What outcome does the photograph imply, and what outcome did the experiment actually measure?
- What additional comparison and follow-up would be needed to connect those outcomes?
- How would you rewrite the headline while preserving the useful finding?
The missing link is the claimed transformation. A faithful description names the measured fuel-use result and the tested conditions. It leaves the longer-term body-composition question open until a suitable comparison addresses it. Notice that this interpretation does not require dismissing the experiment: a mechanism result can be valuable without answering every downstream question. This is a reading exercise, not a proposed morning routine.
Hypothetical: “muscle preserved” in a small trial
A fictional trial reports improvement in a maximum-lift test in both groups. The groups received the same dietary instructions, but food records are incomplete. Some participants did not finish. A summary calls the two approaches equally effective and safe, without discussing the missing records, training workload or health assessment.
- Which parts of that summary are supported by the stated measurement?
- What would participant flow and recorded intake add to the interpretation?
- What information would help distinguish strength, muscle growth, tolerability and safety?
Begin with the narrow finding: the measured lift improved among the people represented in the analysis. Then ask for the between-group estimate and its uncertainty, the measurement of muscle size, reasons for missing follow-up and the method used to assess adverse outcomes. Equal dietary instructions alone cannot confirm equal intake. The next step is to inspect those details, not to invent either a benefit or a harm. The scenario illustrates evidence appraisal rather than a training decision for an individual.
WHERE THE EVIDENCE STOPS
What would make the answer more convincing?
- Would longer studies with larger samples detect meaningful differences that short trials cannot resolve?
- What changes when workout feeding state is varied while the eating window, food provision and training are otherwise held constant?
- How well do these results transfer to older adults, different training demands or clinical populations?
- Which measurements best capture recovery, sustained participation and repeated high-intensity performance?
Questions worth taking into a conversation.
Use these to prepare for an individual discussion with a qualified clinician, sports dietitian, or coach as appropriate to the question.
- Which outcome would you choose before reading the results, and would the paper actually answer it?
- Where does the paper describe what participants did rather than what they were instructed to do?
- What is the strongest conclusion you can write without removing the uncertainty?
- What single design change would most improve confidence in the next study?