Have you ever been frustrated while exercising with your husband, boyfriend or male buddies because you seem to get hungry and/or thirsty before they do? It just seems like even though you are strong and fit they can go forever and not have to eat or drink. This can be very frustrating for female athletes and some assume this difference somehow reflects weakness. The reality is there are physiological reasons for this phenomenon and they are related to glycogen not weakness.

Glycogen is the storage form of carbohydrate and the main fuel source for moderate to high intensity exercise as well as our brain’s preferred fuel. Our muscle mass determines the amount of glycogen we have on board. Since men generally have more muscle or lean mass than women do, they are able to store more glycogen. Smaller women with less body mass will also have less room to store glycogen than taller or bigger women.

Glycogen is also stored with water so more glycogen also means more stored water. So, without accounting for particular fitness levels men can typically go longer without eating or drinking than women can. The bottom line though is that with less glycogen in our reserves we will need to re-fuel more often than our male counterparts. We must also be savvy about replenishing our glycogen stores after exercise particularly if we plan to exercise the next day.

Many recreational athletes are not well educated about the issue of glycogen stores for physical activity. In the present carbohydrate-phobic culture, many women eschew carbs to manage their weight, assuming their bodies can use its own fat stores for energy. While it is true that carbohydrate, fat and protein may all be used for energy, carbohydrates are more quickly and efficiently converted to energy particularly when oxygen is not abundant. This means when we are working harder during moderate to high intensity activities, exercising at high altitudes (above 5,000 feet) or in hot or cold environments we use more carbohydrate than fat.

The caveat here is that training increases our ability to use fat for fuel at a higher intensity level than less-trained athletes. Training also increases our muscle mass thereby increasing glycogen stores by 20% – 50% making more total fuel available – with or without adequate oxygen. The glycogen issue for more hard-core athletes is related to over training. Without proper rest in training cycles glycogen stores are not adequately replenished. This raises the risk of injury, illness and poor performance. It can take up to 20 hours to fully replenish glycogen stores after an endurance activity or a series of days without proper glycogen repletion. The effects of glycogen depletion are cumulative. If we don’t fully replenish the supply after a work out we enter the next work out partially depleted.

So how much carbohydrate do we need for our glycogen stores? This varies individually but the general recommendation is 4-5 grams of carbohydrate per pound of body-weight. Since most of us have no idea how much glycogen we use during our various activities we need to be conscious of including carbohydrates before and after exercise. For bouts of exercise lasting 90 minutes or more and during high intensity sprinting, athletes may benefit from carbs during exercise as well. This can be in liquid form such as a sports beverage or a gel – both more practical options for high intensity activities.

The type of carbohydrate also matters for optimal performance. Within two hours of or during exercise more simple, easily digested carbs are better. Some examples are bagels, fruit, yogurt and some cereals. Limiting fat, fiber and protein at meals or snacks prior to and during exercise is also prudent for optimal digestion. So high fiber whole-grain bread spread with peanut butter and jelly may be the perfect fuel for post-exercise fuel or while out hiking, climbing, boating, and skiing but not a good choice prior to running, strenuous biking or an ice hockey game. In general, the carbohydrate food chosen depends on the amount of time available for digestion and personal preferences.

So, as female athletes we need to honor our body signals to eat and drink, even if our male companions aren’t on the same feeding schedule. It is not a matter of being weak or wimpy – it is just a biological gender difference. Despite many claims to the contrary, carbs alone are not responsible for excess weight and a high protein regimen is not appropriate for most athletes, male or female. Remember that if you choose not to fuel as needed you will not perform at your best and probably feel crummy afterwards. It is also worth thinking about the old tortoise and hare scenario – slow and steady often does win the race!

Mary Ryan is a Registered Dietitian with a Master of Science Degree in Foods & Nutrition. Beyond Broccoli is her Jackson Hole-based Nutrition Counseling and Education Practice. She enjoys many activities with and without her husband (and he appreciates that she is not crabby if she eats and drinks when she needs to!). If you have nutrition questions you would like addressed contact her at mary@beyondbroccoli.com.