The Formula of Fitness Fueling

By Stevie Lyn Smith, MS, RDN, CSSD, CDN, November 17, 2021



Whether you’re an avid runner, casual gym-goer, or high-level athlete your nutrition habits, practices, and regimen has probably crossed your mind. We have all spent time looking at the latest nutrition trends, pictures, and recommendations that flood across social media channels. With the overwhelming amount of information, it can be challenging to figure out what you should be doing to support your active lifestyle. All activities are not created equal, so we break down how to fuel your body to give it what it needs to perform and recover!



Calories are the first piece of the puzzle when looking at maintaining a healthy and active lifestyle. According to the International Society of Sports Nutrition, those who participate in a general fitness program (30-40 minutes per day 3 times a week) can usually meet their nutritional needs by following a normal, balanced diet as their caloric demands are around 200-400 calories per session.1

 When we look at athletes at moderate intensity levels, the caloric burns are significantly higher at upwards to 600-1200 kcals per hour. This will continue to increase as the t does and during higher volume training weeks. Elite and professional athletes will exceed these levels significantly as the workout intensifies.1 

So what does this all mean? The focus should be to make sure you’re getting enough calories to offset your energy expenditure. When you’re trying to perform at workouts, but remain in a constant caloric deficit, this can result in negative physical and psychological outcomes. These can include illness, reduced sleep quality, incomplete recovery, and hormonal fluctuations increased resting heart rate, apathy towards training and increased stress.1

 Diving deeper than simply just eating enough calories, athletes, in particular, should be mindful of the kinds of foods and more specifically what macro and micronutrients they provide.


Carbohydrates are your friends

There is no lack of research out there that emphasizes the importance of carbohydrates, especially for those athletes who are looking to perform in team sports or endurance racing. When athletes compete in events up to three hours carbohydrates are the predominant fuel source used by working muscles.2 

Endurance athletes are encouraged to consume carbohydrates before, during (depending on the duration of the session), and after exercise to optimize performance and ensure there is enough carbohydrates readily available for your training sessions. Replenishing carbohydrates after moderate to high-intensity exercise will restore glycogen levels, the stored form of carbohydrates, in both the muscles and liver. This will promote adequate recovery after sessions and adequate caloric intake, as energy restriction tends to interfere with an athlete's ability to meet their higher carbohydrate needs.3

While those who participate in a general fitness program can meet their carbohydrate needs by consuming a normal diet (3-5g/kg/day1), moderate and high-volume athletes will need to focus on getting more carbs in; 5-8g/kg/day for moderate levels of training and 8-10g/kg/day for high intensity and levels of training to maintain muscle glycogen levels.4 

These carbs should ideally be coming from a diet rich in vegetables, fruits, legumes, and whole grains to provide a range of vitamins and minerals. When exercising at a moderate to high intensity for longer than 2 hours it is recommended that carbs be taken in session to prevent fatigue and improve performance.2 Ideally, these carbs should come from easily digested sources such as sports drinks, gels, and chews. This has also been shown to be beneficial in athletes participating in intermittent or team sports when the intensity, duration, and pre-competition intake of carbs are taken into consideration.2


Protein is for everyone

  • Getting enough protein in your diet is key to promote muscle recovery, prevent muscle breakdown, and prevent injuries. Athletes who are susceptible to protein malnutrition include runners, cyclists, and triathletes.1
  • Recent research shows that getting twice the RDA, 1.3-1.8 g/kg/day to be beneficial for athletes who participate in intense training.1,5 
  • For general exercisers, protein needs are also recommended to be above the RDA with 1.62 g/kg/day being the recommended staring goal.
  • For athletes training at moderate levels 1.2-2.0 g/kg/day is the goal and 1.7-2.0 g/kg/day for high intensity athletes.1,6

It's not simply about getting enough protein but focusing on getting high-quality sources. Different types of protein are broken down and absorbed at varying rates. Opt for foods like chicken, fish, egg whites, and lean cuts of beef. Protein powders made from whey, egg and pea protein are great for meeting protein needs, but choose food sources whenever you can. Spacing out your protein every 3-4 hours in ~20g portions has been shown to have the greatest effect on muscle growth and repair.1


Fat shouldn’t be feared

In a world where we've gone from low fat to high-fat diets, this brings up lots of controversy for athletes. Getting adequate fat helps to maintain energy balance, replenishes intramuscular triacylglycerol stores, and ensures that we are getting enough essential fatty acids.1 

While past research shows a high-fat diet providing no performance benefits and increased gastrointestinal issues, more recent studies show limited, mixed results on the efficacy of a high-fat diet, ketogenic diet for athletes.1 A moderate amount of fat, about 30% of caloric intake, is recommended for athletes to achieve adequate intake while keeping carbs and protein at ideal amounts.1 

When looking for fat sources in your diet strive for mostly unsaturated fats; think avocados, walnuts, flax, and canola oil while limiting saturated fats found in animal products and processed foods as much as possible!


How do you know if you’re getting enough?

Some simple signs that you may be falling short in getting any or all of these include weight loss, inability to maintain weight and/or lean body mass, failed workouts, lack of performance improvements, fatigue, illness, and poor sleep quality.

Tracking calories and macronutrients with apps like MyFitnessPal can be a helpful tool and strategy for some athletes. Putting a focus on a balanced diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats throughout the day with proper fueling pre and post workout is key. Knowing that when you are training more and with more intensity, you will need more to meet the increased demands you are putting on your body!


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1.     Kerksick C, Wilborn C, Roberts M et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15(1). doi:10.1186/s12970-018-0242-y

2.     Cermak N, van Loon L. The Use of Carbohydrates During Exercise as an Ergogenic Aid. Sports Medicine. 2013;43(11):1139-1155. doi:10.1007/s40279-013-0079-0

3.     Burke L. Energy Needs of Athletes. Canadian Journal of Applied Physiology. 2001;26(S1):S202-S219. doi:10.1139/h2001-055

4.     Burke L, Hawley J, Wong S, Jeukendrup A. Carbohydrates for training and competition. J Sports Sci. 2011;29(sup1):S17-S27. doi:10.1080/02640414.2011.585473

5.     Phillips S, Van Loon L. Dietary protein for athletes: From requirements to optimum adaptation. J Sports Sci. 2011;29(sup1):S29-S38. doi:10.1080/02640414.2011.619204

6.     Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2017;52(6):376-384.

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