REF-954 · Lange et al., 2026 · The Journal of Physiology · Paper · PubMed

Effects of exercise followed by a low-carbohydrate diet on peak fat oxidation and mitochondrial coupling control and efficiency in healthy trained men

C+thin evidenceMeasured on trained athletesWritten before October 2026, being re-checked

The question was how much muscle glycogen content matters for peak fat oxidation (PFO), for the intensity at which PFO occurs (Fatmax), and for mitochondrial coupling control and efficiency (MCCE).

In a randomized crossover, ten trained men did two interventions, each spread over two consecutive days: on Day 1 a graded exercise test and then a glycogen depletion protocol, followed by a high- or low-carbohydrate diet, and the graded test again the next day; muscle biopsies were taken on both days.

PFO rose after both interventions, and rose further after the combined exercise-plus-low-carbohydrate intervention, in which muscle glycogen was low. Only that combined intervention increased Fatmax. Neither intervention changed MCCE.

Participants

Ten trained men (n = 10), healthy. Age, body mass and fitness values are not given in the abstract.

Protocol

Randomized crossover; two interventions, each conducted over two consecutive days; the experiment was repeated after 7-14 days.
Day 1: anthropometric measurements, a blood sample and a muscle biopsy, then a graded exercise test and, after it, a glycogen depletion protocol.
Between the days: a diet high or low in carbohydrate, to manipulate glycogen levels (amounts not given in the abstract).
Next day: a repeat of the blood sample, the muscle biopsy and the graded exercise test.
Muscle samples analysed for glycogen and triacylglycerol content and MCCE.

Key Results

Both interventions raised PFO; the gain was larger after the combined exercise-plus-low-carbohydrate intervention, the condition in which muscle glycogen was low.
Fatmax increased only following the combined exercise and low-carbohydrate intervention.
MCCE was unaffected by the interventions.
Authors' conclusion: glycogen depletion by exercise, combined with a low-carbohydrate diet, raises PFO and Fatmax but leaves MCCE untouched; changes in mitochondrial function are not what regulates this.
The abstract gives no effect sizes, rates or p-values.

Practical Application

"If I do a hard, glycogen-emptying session and then eat low-carbohydrate, will I burn more fat the next day?" In ten trained men (randomized crossover), yes: peak fat oxidation in a graded test the following day rose after the depleting session with either diet and rose further after the low-carbohydrate diet, and the intensity at which fat oxidation peaks (Fatmax) rose only after the low-carbohydrate diet — while mitochondrial coupling control and efficiency did not change. The fuel mix shifted; the mitochondria, as measured here, did not.
This is an acute, next-day measurement. Inference, not tested here: it does not show that the athlete rides or runs faster, and it does not show a training adaptation.
Not from this paper; the base's own practice: keep low-carbohydrate-availability sessions to easy days inside an adequately fed week and fuel the key sessions (SYNTH-69, REF-543); training low also raised the protein requirement in REF-726.
Not from this paper: a multi-week sleep-low block with a performance outcome is in REF-003.

Limitations

Ten men; no women; "trained" is not quantified in the abstract.
Acute design over two consecutive days; no training block, no performance test.
No numbers for the size of the PFO or Fatmax change, and no diet composition, are given in the abstract.
Online ahead of print. Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

crossover with ten men; mechanistic (whole-body and muscle measurements), no performance outcome