By Kelly Jones MS, RD, CSSD, LDN

With Americans having more exposure to group fitness instructors and personal trainers, it’s easy for inaccurate information to spread when it comes to fueling the body for physical activity. To better understand how to eat to support exercise, it’s helpful to have knowledge of how the body uses nutrients to support energy levels for exercise as well as recovery.

Macronutrients for Fitness

There are three macronutrients – carbohydrate, fat and protein. All are necessary to optimally fuel your active body and central nervous system, even on rest days. Cutting out any of these nutrients can lead to detrimental effects on health and performance. They are the only nutrients that provide us with energy – otherwise known as calories – and as their name suggests, we need a lot of them!

Carbohydrates for Fitness

Contrary to popular belief, carbohydrates are not the enemy. In fact, they should be the body’s primary energy source. They’re the preferred energy for the central nervous system and muscles, among many other body functions. Carbohydrates also provide a protein-sparing action — they are used for energy so that protein can be used for its critical roles such as tissue creation and immune support. 

Cutting carbs often just leads to craving them more, since the body is wired to use them. Think about “blood sugar”. Its purpose is to have a constant supply of energy running through our circulatory system so that cells are able to obtain it consistently. What happens when blood sugar drops? Well, if you don’t take in carbohydrates when you need them, you may find yourself irritable, overly hungry, maybe even dizzy or with a headache. Later, you may overeat, over-compensating for what you didn’t provide your body with earlier.

If you’re an athlete or an active individual, carbohydrates are especially important. Carbohydrates are stored in the muscles as glycogen so that they’re ready to go when exercise begins. Muscle glycogen and blood carbohydrate are most helpful to fuel exercise of high intensity and long duration. Liver glycogen is also stored to help keep blood sugar levels normal during activity (as well as between meals and when we’re sleeping at night). Therefore, decreased carbohydrate consumption can negatively impact training and performance — you can relate it to a car running out of fuel.

It’s pretty simple to identify carb sources. Was what you’re eating originally a plant? Other than the carbohydrate in dairy – lactose – or honey, all other carbs come from plant foods like fruits and vegetables, whole grains, legumes, nuts, and seeds. Those that are more easily digested, such as fruit, starches low in fiber, and honey, are best for snacks before exercise and for ingestion during activity lasting longer than an hour.

Dietary Protein for Fitness

Rather than be a significant energy source, protein is best suited as a structural and metabolic nutrient. In addition to muscle, it also builds all of our organ tissues, makes the framework of our bones, and creates compounds like immune proteins, hormones, and enzymes to protect the body and regulate metabolism. It’s important to note that over-consuming protein won’t lead to extra muscle gain; instead, it will just be excreted. This is why dietitians recommend eating moderate amounts of protein with all meals and snacks (except for snacks immediately prior to exercise) rather than a lot of protein just post-workout and at dinner.

While the minimum protein recommendation for adults is 0.8g/kg per day, that amount is the bare minimum to support basic body functions and prevent deficiency. For those looking to support a lifestyle with moderate physical activity, 1.0 g/kg may be more beneficial. Still, athletes and those engaging in endurance and strength training programs require somewhere between 1.4-2 g/kg per day. 

It’s no secret you can get protein from meat, but you also obtain high-quality protein from foods like eggs, fish, soy products, peas, beans, and lentils. Grab a few more grams from nuts, seeds, whole grains, and even vegetables! These foods contain varied macronutrients for fitness and health.

Dietary Fat for Fitness

Fats are often ignored when covering macronutrients for fitness, as intake of them isn’t as important immediately before or after exercise. Fats are a necessary energy to store on our bodies. They provide us with energy at rest for basic body functions like temperature regulation and are a good source of fuel for lower intensity and long duration exercise. On top of being an energy source, fats are important for proper inflammatory responses for recovery, joint lubrication and protection, nutrient absorption, and even brain function. They also help us feel satisfied when we eat meals and snacks, so be sure to include a fat source each time you eat. 

There are many classifications of fats occurring in nature – and believe it or not, all can have a place within your diet. Mono-unsaturated, poly-unsaturated, and saturated fats may all be familiar terms. Mono-and polyunsaturated sources are important for improving brain health, joint fluidity, muscle recovery, and have an anti-inflammatory effect when consumed in adequate quantities and appropriate ratios to one another. Saturated fats, which should be limited, are impossible to eliminate from the diet as even our healthiest fat sources – like olives and avocados – contain some saturated fat. It’s all about balance!

By choosing fats coming from plant foods and from fish, such as avocados, olives, nuts, seeds, and salmon, tuna, anchovies, etc., you’ll naturally obtain more of the beneficial fats and less of ones you don’t need much of.  

Saturated fat is found in meats, butter, cheese, many fried foods, and baked goods. These foods can be included in your diet, but in a way that promotes a mindful indulgence. It may be best to avoid these foods in large amounts before a workout or the night before a race, too.

Key takeaways on nutrition for fitness:

-Eat carbohydrate, protein, and fat at all meals and snacks, with a smaller emphasis on protein and fat pre-workout. 

-Spread protein intake throughout the day versus eating a lot at once.

– Before exercise, focus on eating easily digestible carbohydrates to provide quick energy to the body without risking gastrointestinal discomfort.

-After exercise, reach for both protein and carbohydrates. This is so protein can focus on the repair and recovery process rather than risk being used as energy and compromising muscle repair. The carbohydrates will replenish glycogen and provide energy to the bloodstream as well.

-Choose more fats from plant and fish sources rather than animal. This boosts intake of mono-unsaturated and omega-3 fatty acids, which support healthy inflammatory responses.

Kelly is a sports dietitian who also works on the media and communications side of nutrition. She shares recipes and tips for fueling active lifestyles with a plant-forward approach on her website, Instagram, and Facebook. She resides outside of Philadelphia in Bucks County and works with clients both locally and nationally.