REF-1205 · Tarnopolsky et al., 2001 · Journal of Applied Physiology · Paper · PubMed

Do women need a different carbohydrate load than men?

Not a different one, enough of it: in 12 trained athletes, women's glycogen rose only when total energy rose with the carbohydrate share. Set it in g/kg, not %. Abstract only.

Blimited evidenceMeasured on trained to highly trained athletes

An earlier study by the same group (Tarnopolsky et al. 1995, J Appl Physiol 78:1360-8) had found that trained women did not raise muscle glycogen when their diet went from 58% to 74% carbohydrate, while men did. That could reflect a lower energy or carbohydrate intake in the women, or a true sex difference in storage capacity.

Here 6 well-trained men and 6 well-trained women were randomly allocated to three 4-day diets before a biopsy: habitual (Hab), high carbohydrate at 75% of energy (CHO), and high carbohydrate with about 34% extra energy (CHO + E). Total glycogen was higher than habitual on both CHO and CHO + E in the men (P < 0.05), but only on CHO + E in the women (P < 0.05).

Proglycogen and macroglycogen proportions and hexokinase activity did not differ between the sexes. The authors conclude that a low energy intake may explain the lower capacity to load reported in women.

Our reading: the abstract is consistent with the later finding of no sex difference when intake per kilogram is matched (REF-1206; summarised descriptively across studies in REF-1204, which did not pool or test sex) and argues for prescribing a load in grams per kilogram rather than as a percentage of energy, as the current consensus does (REF-748); with six per group and no numbers in the abstract, it is a direction, not a dose.

Protocol

Design (from the abstract): n = 12 well-trained endurance athletes (6 men, 6 women), randomly allocated to three diets, each for a 4-day period before a muscle biopsy (the abstract's wording); analyses of total, pro- and macroglycogen and hexokinase activity.
Diets: Hab = habitual; CHO = 75% of energy from carbohydrate (up from 58%); CHO + E = 75% carbohydrate with about 34% more energy.
Not given in the abstract: the order and spacing of the diets, menstrual phase or contraceptive use, the training or depleting exercise before and during the diets, the absolute carbohydrate intakes (g/kg/day), the biopsy site, the statistics beyond P < 0.05, and funding.

Key Results

Diet (4 days)Men (n = 6)Women (n = 6)
Habitualreferencereference
75% carbohydratetotal glycogen higher than habitual (P < 0.05)not different from habitual
75% carbohydrate + ~34% extra energyhigher than habitual (P < 0.05)higher than habitual (P < 0.05)
No sex difference in the proportion of pro- and macroglycogen or in muscle hexokinase activity.
Glycogen values, intakes in g/kg and between-diet differences are not given in the abstract.
Secondary source, not this abstract: the Jones 2026 review (REF-1204, full-text Table 1) tabulates this study as 6 men and 7 women, with intakes and dry-mass glycogen of 6.1, 7.9 and 10.5 g/kg/day → 537.2, 660.2 and 741.1 mmol/kg in the men (habitual, CHO, CHO + E) and 5.1, 6.4 and 8.8 g/kg/day → 629.1, 650.6 and 737.7 mmol/kg in the women. On those figures the women's "75% carbohydrate" diet was only 6.4 g/kg/day, while the men's was 7.9.
A number that does not add up: the abstract gives 6 women; the review's table lists 7. Which is right cannot be settled from the abstract.

Mechanisms

Measured: hexokinase activity and the pro- and macroglycogen proportions did not differ between men and women.
Authors' interpretation: the women's earlier failure to load reflected a low energy intake rather than a lower capacity to store glycogen.
Inference: a percentage of a smaller energy intake is a smaller amount of carbohydrate. At 2,200 kcal a day, 75% from carbohydrate is about 410 g, or 6.9 g/kg for a 60-kg athlete (our arithmetic) — below the more than 8 g/kg/day that the REF-1204 authors give as their practical loading rule (their synthesis, not a pooled estimate; the pooled threshold was 6.5 g/kg/day).

Practical Application

Do women need a different carbohydrate load than men? Not a different one, enough of it: in 12 trained athletes, women's glycogen rose only when total energy rose with the carbohydrate share. Set it in g/kg, not %. Abstract only.
Prescribe in grams per kilogram: the consensus states daily carbohydrate in g/kg (REF-748, A: 10-12 g/kg/day for 1-2 days before a single-day event), and SYNTH-69 already says g/kg, not a share of energy. This study is the reason that matters most for women and for any athlete eating little.
Check total energy before blaming biology: a woman who "cannot carb-load" may simply be eating too little overall; screen for low energy availability (SYNTH-54). Not from this study; the base's own practice: write the load as a menu in grams and check it against body mass.
Menstrual phase: not reported in the abstract; at about 10 g/kg body mass REF-1206 reported similar rises in both phases (no statistics in its abstract), and the cycle is coached by symptoms in SYNTH-37.
Does loading pay at all: only for events beyond about 90 min (REF-819, B+).

Limitations

Abstract only. The full text (APS) could not be retrieved, so diet order, washout, menstrual phase, exercise during the diets, absolute intakes and the size of every difference are unknown here; the g/kg figures above come from a review's table, not from this abstract.
Six per sex (or seven women by the review's count); a non-significant change in the women on the 75% diet is no evidence of a difference, not proof of no rise.
Glycogen only, biopsy site not given in the abstract; no performance outcome.
Energy and carbohydrate rose together in the CHO + E diet, so the abstract cannot say whether the extra carbohydrate grams or the extra energy did the work; the authors' reading is energy.
Funding and conflicts: not given in the abstract.
How this entry was checked and changed
Why this level

from the abstract; small trial (n = 12: 6 men, 6 women), glycogen outcome only, no performance test