By Coach Matt Russ

We are all creatures of routine, and our diets are no exception. Time-strapped athletes, in particular, tend to gravitate toward the same foods and supplements that allow them to fuel their bodies quickly and conveniently.

But a properly designed training plan is not static. Training intensity and duration change throughout the day, week, and season, which means an athlete's energy requirements change as well.

This is where nutrition periodization becomes important.

The basic concept is to match your nutrition to the demands of the training phase you are in. An athlete may need more energy and carbohydrate during periods of heavy training and less energy when training volume and intensity are reduced.

It is equally important to make smaller adjustments to your diet from day to day. The difference in energy expenditure between a rest or recovery day and a demanding training day can be substantial. Adjusting your food intake accordingly can help maintain energy balance and your desired race weight throughout the season.

Reduce Energy Density on Rest Days

On a rest day, your caloric expenditure may be significantly lower than it is on a heavy training day. If you consistently consume more energy than you use, even relatively small daily surpluses can accumulate over time.

One way to compensate is to reduce the energy density of your meals and snacks without eliminating important nutrients.

For example, on lower-volume days, you can emphasize foods such as fruits, vegetables, yogurt, cottage cheese, and other nutrient-dense foods while reducing portions of more calorie-dense carbohydrate foods such as pasta, bagels, bread, and potatoes when those larger portions are not required to support training.

The goal is not to eliminate carbohydrates. Carbohydrates remain an important part of an athlete's diet. The goal is to adjust the quantity to match the day's training demands.

Watch the Sports Nutrition Products

Energy bars, gels, sports drinks, recovery shakes, and other sports nutrition products have an important place in an athlete's training program. However, they are designed primarily to provide convenient energy and nutrients before, during, or after training.

If you are having a recovery day with little or no training, you may not need the same supplemental calories you would consume after a demanding workout.

On lighter training days, consider reducing the serving size of sports nutrition products when appropriate. For lower-intensity workouts lasting less than roughly 60–90 minutes, water may be sufficient for hydration in many circumstances, although heat, humidity, individual sweat rate, and other factors can change those requirements.

You can also modify calorie-dense recovery shakes on rest days by using water and ice rather than higher-calorie ingredients such as milk or yogurt when those additional calories are not needed.

The important point is to distinguish fueling for training from eating out of habit.

Portion Control Matters

Portion size is one of the simplest ways to adjust daily calorie intake. On rest and recovery days, reducing portions can help lower overall energy intake while maintaining an appropriate balance of protein, carbohydrates, and dietary fat.

Athletes may also find it easier to manage their weight when their everyday diet is built primarily around minimally processed, nutrient-dense foods.

Fresh or frozen fruits and vegetables, whole grains, and lean protein sources such as fish, poultry, eggs, tofu, and other soy products can form the foundation of a well-balanced athletic diet. Vegetarian athletes have numerous options for obtaining adequate protein while managing overall calorie intake.

Reducing calories on a recovery day can also mean passing on some of the desserts, snacks, and other discretionary foods that may fit more easily into the diet on a demanding training day.

Plan Your Meals

Planning is one of the most effective tools for managing nutrition.

When you already know what you are going to eat, you are less likely to make decisions based solely on convenience or hunger. Planning can be as simple as making a grocery list, preparing meals ahead of time, or choosing a restaurant that offers nutritious options.

The objective is not to create a rigid diet. Rather, planning gives you control over your available choices and makes it easier to match your food intake to your training.

What About Glycogen?

Glycogen is the stored form of carbohydrate found primarily in the muscles and liver. Glycogen stores can become depleted during prolonged or intense exercise and can be replenished through carbohydrate intake and recovery.

One reason athletes may see their body weight change noticeably after several rest days is glycogen replenishment. Glycogen is stored along with water, so restoring depleted glycogen stores can result in a relatively rapid increase in scale weight.

This is important when monitoring race weight.

An athlete may step on the scale after several days of rest and see several additional pounds without having gained the equivalent amount of body fat. Some of that change can be explained by replenished glycogen and associated water.

You may also notice that your workout quality improves after several rest days. That improvement can be the result of recovery as well as restored energy and glycogen stores.

This is why athletes need to understand their fully replenished body weight rather than reacting to every short-term fluctuation on the scale.

Don't Cut Calories When You Need to Replenish

Maintaining an appropriate race weight while consuming enough energy to support training can be a delicate balance.

If you have been training heavily and find yourself several pounds below your normal, fully replenished weight, cutting calories simply because it is a rest day may not be appropriate. Your body may need those calories and carbohydrates to restore energy and glycogen stores.

On the other hand, if you consistently consume the same amount of food regardless of whether you are completing a three-hour workout or taking a complete rest day, you may be taking in considerably more energy than you need on low-activity days.

The goal is to understand your individual requirements rather than applying the same calorie target every day.

Find Your Individual Calorie Requirements

Weight maintenance for an endurance athlete is ultimately a balancing act between energy expenditure and energy intake.

Every athlete has different requirements based on body size, training volume, exercise intensity, metabolism, occupation, daily activity, recovery, and other individual factors. There is no single calorie target that works for everyone.

Metabolic testing can provide information about an athlete's individual energy requirements, while tracking training volume and estimated exercise energy expenditure can provide another useful reference point.

Many heart-rate monitors and training devices estimate calories burned during exercise. These estimates are not perfect, but they can provide useful information when considered alongside your body weight, training performance, hunger, recovery, and overall energy intake.

It is also helpful to understand the approximate calorie content of the foods you regularly eat. You do not need to weigh and measure every bite for the rest of your life. Having a general understanding of portion sizes and energy density can make it easier to adjust your intake as training demands change.

There is considerable room for flexibility, but the objective is to avoid tipping the energy balance too far in either direction.

Nutrition Should Match the Training

Nutrition periodization does not mean following a complicated diet. It means recognizing that your nutritional requirements change as your training changes.

Heavy training requires adequate fuel. Recovery requires adequate nutrition. Rest days may require less energy than demanding training days.

Learning to make these small adjustments can help an endurance athlete maintain energy availability, support recovery, replenish glycogen, and manage body weight throughout the training season.

The key is to stop thinking of nutrition as a fixed daily routine and instead view it as another component of the training plan—one that should change as the demands placed on the body change.

Matt Russ enjoyed a professional coaching career spanning over two decades of working with professional endurance athletes. His athletes have achieved numerous regional, national, international and championship titles under his direction. Matt achieved the highest level of licensing by both USA Triathlon and USA Cycling, and was a licensed USA Track and Field Coach. His accomplishments include being named "Team USA" Coach for the 2011 Beijing World Championship. Head Coach and founder of The Sport Factory, a USA Triathlon Certified Performance Center, he has authored many articles on a wide variety of endurance related topics.