This is such an important question because there isn’t as much research done on female endurance athletes. Much of the studies that we see regarding fueling and carb intake have been done on men.

And as Dr. Stacy Sims says,” Women are not small men. Stop eating and training like one”. There are a few variables that influence how our bodies process fuel and that includes our hormonal cycle.

For example, during the luteal phase (where hormones are high from days 15-28 of the cycle) your blood sugar will fluctuate more, breathing rate increases, plasma volume and sodium levels decrease, and you may feel weaker. To combat some of this you’ll need more sodium, fluids, and carbs during training. Women who deal with GI distress find that they can deal with more bloating and GI issues during this part of the cycle.

An important thing to remember for both men and women is that you’re not looking to replace all the calories you burn while running. The body can only process so many calories per hour (and this is reduced while running because much of the blood flow is shunted away from digestion to the larger muscle groups).

Typically a range of 120-200 calories per hour works for most runners (women will be on the smaller end of this equation). Larger persons and those with extremely high metabolic rates may need a bit more.

In her book Roar- How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life, Dr. Stacy Sims goes into female specific research. She says that women should aim for 0.9-1.3 percent of their body weight per pound in calories per hour. I’d definitely recommend that you read that helpful book.