A well cited trial had reported that women do not have the capacity to accumulate supranormal muscle glycogen. The authors noticed that in that trial the carbohydrate given to the women, relative to body mass, was much lower than what the men received, because the dose had been set as a percentage of what each person already ate.
Their stated primary aim was to re examine the question with the two groups fed comparable amounts of carbohydrate.
Drawn from the paper's introduction.
Endurance trained women and men were fed 12 grams of carbohydrate per kilogram of lean body mass per day for three days while stopping their usual training.
In the women, muscle glycogen rose from 108 to 193 millimoles per kilogram of wet weight in the post menstrual phase, and from 111 to 202 in the pre menstrual phase. In the men it rose from 109 to 183.
The authors conclude that female athletes do have the capacity to accumulate supranormal muscle glycogen, and that when trained men and women are fed comparable amounts of carbohydrate relative to lean body mass there is no sex related difference in that capacity.
| Women, post menstrual phase | 108 (15) to 193 (14) mmol/kg wet weight |
| Women, pre menstrual phase | 111 (16) to 202 (20) mmol/kg wet weight |
| Men | 109 (27) to 183 (25) mmol/kg wet weight |
| Carbohydrate dose | 12 g/kg lean body mass per day for 3 days |
| Sex related difference in loading capacity | none found |
Proposed by the authors This is the explanation the authors offer in their discussion. This study did not test it.
The explanation the authors offer is arithmetic rather than physiological. Prescribing carbohydrate as a percentage of what someone already eats hands a smaller absolute dose to the smaller person, and in the earlier trial the women's intake relative to body mass was much lower than the men's.
Change the denominator to lean body mass, so that both groups receive a comparable amount of carbohydrate for the muscle they are actually carrying, and the reported difference between the sexes does not appear.
Drawn from the paper's introduction and conclusions.
The claim that women cannot carbohydrate load, which came out of a widely cited trial and travelled a long way on its own, does not survive changing the denominator of the dose. This contradicts the earlier finding, and the later meta analysis reads it the same way, noting that the one study reporting a sex difference had given the women far less energy.
Endurance trained women and men fed 12 grams of carbohydrate per kilogram of lean body mass per day for three days while not training.
A single trial feeding both denominators, by percentage of habitual energy and by lean mass, in the same participants, which would put the two prescriptions side by side for the first time.
Newsletter
Each issue by email, when the newsletter launches. Leaving your address puts you on the list, nothing is sent yet.