Despite their bad reputation, carbs are not the enemy.
The media floods women with confusing and even conflicting messages around diet and exercise. Popular trends such as intermittent fasting, low carb, and ketogenic diets can leave women wondering if limiting the amount of time dedicated to eating or the amount of carbohydrates they are consuming can help them fast-track their fitness goals.
Despite their bad reputation in certain circles, carbs are not the enemy. In fact, skipping carbs can be detrimental to overall performance and fitness goals. Female athletes need carbs and will achieve their performance and body composition goals more effectively by fueling for performance.
Why Carbs Are Essential For Performance
No matter what your training goals — building lean muscle, increasing power, strength, or endurance— adequate carbohydrate consumption improves performance towards these outcomes. Carbs provide 50% of energy that athletes need for moderate intensity activity, and up to 100% for high intensity activity. The more vigorous the activity, the more the body relies on glucose and glycogen (the body’s form of stored carbohydrates). Glucose availability is the single biggest limiting factor for going strong and maintaining effort and intensity for any type of exercise. Studies consistently show an improvement of 2-6% in performance after athletes ingest carbs compared to water alone during intensive exercise lasting longer than 2 hours. With the right fuel on board, athletes can maximize their training adaptations and extend their ability to go longer, harder and burn more calories in each training session.
Intermittent Fasting
Historically many people used fasting as part of a spiritual or religious practice, but today many people start fasting for health reasons. Intermittent Fasting (IF) is a pattern of eating that switches between periods of fasting and eating. Fasts can range in length from multi-day fasts to “eating windows” of 12, 8, or 4 hours a day. Many women engage in Time Restricted Eating (TRE) hoping to improve their metabolic markers, blood sugar control and cardiovascular risk factors.
However, “women need to be aware of the origins of the research. The intermittent fasting and time-restricted (TRE) eating trends originated in obese, sedentary individuals, mainly men, who needed to lose weight quickly for surgery and/or to have some semblance of blood sugar control to start diabetic therapy," says Dr. Stacy Sims, an exercise physiologist and nutrition scientist.
"What has not been studied in depth is the effects of IF and TRE on healthy, physically active women. What we do see is an increase in low energy availability, an increase in sympathetic drive, and an increase in thyroid and endocrine dysfunction in healthy, physically active women following these trends,” Dr. Sims adds.
One recent study, (West 2012), showed that women performed better in endurance exercise after having a morning meal that included carbohydrates versus a fasted training state. For active women this means having adequate nutrition before engaging in tough training sessions will result in better performance outcomes. Although it is possible for female athletes to engage in intermittent fasting, it appears better for overall health and performance if they aren’t exercising in a fasted state.
Low Carb Diets and the Keto Diet
The case for low carb diet trends is usually made with the promise that the body will burn more fat. Low carb diets simply aim to reduce the overall amount of carbohydrates within the diet. Conversely the ketogenic diet is a high fat diet with drastic carbohydrate restriction in the attempt to burn more fat for energy. However, due to sex differences in women that "tell" the muscles to use more fatty acids, it's not necessary to do a special diet to make this happen, according to Dr. Sims. Women who are focused on performance goals, a leaner physique, or health benefits such as insulin sensitivity and blood glucose control would do better to focus on high intensity exercise because it’s a stronger adaptive stress for these type of results.
Moderate to high-intensity training sessions produce a strong, sharp stimulus that helps build lean muscle, power and speed development and burns more calories in a shorter period of time. When training at peak levels of intensity the body needs its optimal fuel source, carbohydrates, to perform well. Low carb diets impair the body’s ability to perform at these high intensities, and are counter-productive to achieving performance goals. By going low carb, not only are women undermining their goals, but training in this fasted state puts a tremendous amount of stress on women’s bodies.
“Women of reproductive age need to be particularly careful with intermittent fasting as their bodies are more sensitive to stressors like prolonged fasting and caloric restriction” explains Jillian Greaves M.P.H., R.D., L.D.N Integrative Functional Dietitian at Prevention Pantry Nutrition. She goes on to explain that “IF might do more harm than good. Fasting increases cortisol which can lead to blood sugar dysregulation, increased insulin resistance, lean muscle loss, fatigue and disruptions to thyroid over time.”
Fueling for Performance
When fueling for performance, it’s important to strike a balance. It's well established that consuming too many calories results in weight-gain, but failing to consume adequate calories also has negative outcomes like reduced performance and risk factors associated with Low-Energy Availability (a state where there is not enough energy left to support the body optimally). The best approach is to “fuel for the work required” by ensuring that daily caloric requirements are being met and there is sufficient amounts of muscle glycogen to support high-quality training sessions. Fueling properly both before and after exercise sessions helps maximize training adaptations and recovery. Daily carbohydrate needs are determined by the intensity, duration and frequency of the work being performed.
From a body-composition and performance standpoint it’s generally best to aim for a daily carbohydrate intake of 40-45% of your total calories. However athletes engaging in long endurance sessions of 4+ hours may need upwards to 8-12g/kg/day. This doesn’t necessarily mean that athletes need to pile their plates high with bread and pasta. Colorful fruits and vegetables are filled with vitamins, minerals, and phytonutrients which support overall health. Great carbohydrate choices include ancient grains, which tend to be less refined, starchy vegetables like sweet potatoes, yams, winter squash, beets, parsnips, and carrots. These veggies are packed with fiber and antioxidants. Cruciferous vegetables are also a great choice since they help lower the risk of cardiovascular disease, strokes, cancer, and helps reduce high estrogen levels.
For female athletes engaging in moderate to high intensity activities, it’s a balanced diet with adequate calories that includes carbs that will give you the real training advantage.
LISTEN: Biohacking Hormones for Training Advantage with Dr. Stacy Sims
Kristy Appleton is a NASM Certified Personal Trainer and Sports Nutrition Coach who enjoys teaching Power Cycle & Rounds in San Ramon and Berkeley, California Equinox Clubs. Outside of teaching, you’ll find Kristy rock climbing, hiking, biking and kayaking all over Northern California as part of the Women’s Outdoor Adventure Club she founded.