The use of oral contraceptives in women alters the differences in substrate oxidation between phases of the menstrual cycle
Bibliographic record
Abstract
We previously reported that women in the luteal (LUT) phase oxidize less leucine, lipid and lipid relative to CHO as a fuel source, whereas they have a more advantageous protein balance, at rest and during exercise as compared with the follicular (FOL) phase ( Hamadeh et al, Physiologist 2004 ; 47 : 306 – 7 ). Moreover, FOL and LUT women oxidize less leucine and have a less negative protein balance at rest and during exercise as compared with men. To investigate whether this is maintained in women taking oral contraceptives (OC), we measured whole body leucine kinetics using the stable isotope L‐[1‐ 13 C]leucine in 6 women taking triphasic OC and compared the results with those for 12 men at rest and during moderate intensity endurance exercise. The women were tested in the FOL (day 9 ± 2; mean ± SEM) and LUT phases (day 21 ± 1) of the menstrual cycle. Following a primed continuous infusion of L‐[1‐ 13 C]leucine in the postabsorptive state, VCO 2 and steady state breath 13 CO 2 and plasma [ 13 C]α‐KIC enrichments were measured at rest and 60, 75 and 90 min during cycling at an intensity of 65% VO 2 max. Menstrual phase had no effect on any outcome measure. Men had higher leucine Ra (P < 0.004), leucine oxidation (P < 0.005) and protein breakdown (P < 0.004), but lower estimated protein balance (P < 0.005), than women. Men had higher protein synthesis (P = 0.046) as compared with FOL women only. We conclude that OC use in women abolishes the differences in substrate oxidation observed in non‐OC users. Studies measuring substrate oxidation should account for the use of OC in women. (Funded by the Hamilton Health Sciences Foundation and NSERC Canada).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".