There are six groups of essential nutrients that are divided into two categories: micronutrients — containing vitamins, minerals and water; and macronutrients — containing carbohydrates, fats and proteins. The word “essential” means that our bodies do not create these on their own; therefore, they must be consumed exogenously. Underconsuming any of the essential nutrients can lead to a swath of short- and long-term health issues, including fatigue, headaches, poor vision, bad memory, brain fog, poor sleep, general illness and poor athletic performance.

Macronutrient intake recommendations are percentages based on daily calorie requirements. The recommended macronutrient intake formula is to consume 45-65% of your calories from carbohydrates, 10-35% from proteins and 20-35% from fats. Finding your perfect macronutrient balance will never be a constant number, but having the tools to figure out the best starting point will allow you to tweak your meals as needed to best fuel your activities. Then, you’ll be ready to examine nutritional labels and select those foods that best match what your particular physique and activity levels require for optimal health going forward.

How does the body burn calories?

The body uses calories for:

• Mechanical work (muscle movement), such as pumping the heart and breathing
• Transport work, which includes nerve transmission and nutrient absorption
• Synthetic work, like building new cells and tissues

Human bodies are in a constant state of energy expenditure. The ways we burn calories can be categorized into three formulas that together account for our total energy expenditure (TEE):

• Basal Metabolic Rate (BMR) is when your body is burning calories at rest — including lounging, sleeping and general functions like breathing. This is based on a number of factors including metabolism. BMR accounts for 60-70% of TEE.

• Thermal Effect of Food (TEF) accounts for the energy used to digest, absorb and transport nutrients throughout the body. Proteins require more energy (calories) than carbohydrates and both utilize more energy than fat. TEF is 5-10% of TEE.

• Physical Activity includes both unintentional movements (i.e., gesticulating, chores) and intentional movement such as running, biking, walking, weightlifting, etc. Physical activity can be between 15-60% of TEE. 

During exercise, the body uses fat and carbohydrates for energy. The intensity of activity changes the amounts required of each. Our image below gives you an idea of how the body burns calories — and what types — during exercise. Protein is intended for muscle building and repair, and not for exercise energy. If your body doesn’t have enough glucose (the simplest carbohydrate), it will use protein for its energy source; therefore, it’s critical to consume enough carbohydrates to fuel your activity. 

Other factors that impact energy expenditure include amount of rest, stress levels, body composition (muscle mass), hormones and more.  

What are my caloric needs?

In our report, What Should You Eat Before a Workout?, we emphasized that it’s most beneficial for long-term health to consistently engage in a variety of exercises. We also discussed that because there are so many variables affecting the activity and dietary needs of each individual, meal recommendations — and specifically macronutrients — really have to be tailored and personalized. 

It isn’t possible to accurately calculate a person’s TEE outside of a lab, but you can approximate how many calories your body needs on a daily basis, which is called the estimated energy requirement (EER). The EER is the number of calories an individual needs to maintain body weight. To calculate EER, multiply your BMR (see below) by an activity factor (physical activity level, also known as PAL). Once you identify your caloric needs, you can then find a starting point for macronutrients based on the type of activity you’re doing. 

Step 1. Estimating BMR

There are numerous factors that affect BMR: gender, height, weight, age (your BMR decreases by 3-5% each decade after age 30), lean muscle mass, health status, hormones, metabolism, genetics, nutrition status, drug and stimulant use and more. Despite the long list of variables, there is a gold standard formula called the Harris-Benedict equation to use as a starting point, different for males and females. You can also use online calculators such as this one . 

Conversions to remember:
1 kg= 2.2lbs → weight in pounds / 2.2= weight in kg
1cm - 2.54 in → height in inches x 2.54 = height in cm

FEMALE BMR:
10 x weight (kg) + 6.25 x height (cm) - 5 x (age in years) + 5 = BMR calories burned/day

For those who hate math, the equation in Imperial form:
10 x (weight in lbs./2.2) + 6.25 x (height in inches x 2.54) - 5 x (age in years) + 5

For a 35-year-old, 140-lb. female who is 5’5”, the calculation looks like this:
10 x (140 lbs./2.2) + 6.25 x (65 in x 2.54) - 5 x (35 years) + 5
= 10 x 63.64 + 6.25 (165.1) - 175 + 5
= 636.4 + 1031.88 - 180

= 1,486.28 calories burned “at rest”

MALE BMR:
10 x weight (kg) + 6.25 x height (cm) - 5x age (y) - 161

The same equation in Imperial form:
10 x (weight in lbs./2.2) + 6.25 x (height in inches x 2.54) - 5 x (age in years) -161

For a 35-year-old, 170-lb. male who is 5’11”, the calculation looks like this:
10 x (170 lbs/2.2) + 6.25 x (71 in x 2.54) - 5 x (35 years) - 161

= 2,491.13 calories burned “at rest”

Step 2. Incorporating Physical Activity Level (PAL)

Once you’ve calculated your BMR, multiply it by your PAL. Use the table below to estimate your activity level. If our 35-year-old, 140lb., 5’5” female is moderately active, her EER is 2,616 calories per day (BR of 1,486.28 multiplied by 1.76 PAL). 

What are your macronutrient needs?

Now that you know your EER, it’s time to figure out what macronutrients you need to perform at your best, both for exercise and daily living. The beginning of the article outlined the range of macronutrient percentage intakes that are recommended for maintaining a healthy eating pattern. Since carbs, fats and proteins on a food label are listed by weight (in grams), the next step is to take the number of calories you need and convert it into grams of macronutrients. Carbohydrates and protein provide 4 calories per gram and fat provides 9 calories per gram. 

If our 35-year-old female needs 2,616 calories per day, her general recommended macronutrient breakdown looks like this:

Carbohydrates
45-65% of calories
2,616 x .45 = 1,177 calories
1,177 calories / 4 calories per gram = 294 grams of carbohydrates
2,616 x .65 - 1,700 calories
1,700 calories / 4 calories per gram = 425 grams of carbohydrates

Recommended intake: 294-425 grams of carbohydrates/day

Protein
10-35% of calories
2,616 x .10 = 262 calories
262 calories / 4 calories per gram = 65 grams of protein
2,616 x .35 - 916 calories
916 calories / 4 calories per gram = 229 grams of protein

Recommended intake: 65-229 grams of protein/day

Fat
20-35% of calories
2,616 x .20 = 523 calories
523 calories / 9 calories per gram = 58 grams of carbohydrates
2,616 x .35 - 916 calories
916 calories / 4 calories per gram = 102 grams of fat

Recommended intake: 58-102 grams of fat/day

To maximize performance, athletes can adjust their macronutrient ranges to find an optimal range based on activity intensity for carbohydrates and goals for protein. The remaining calories can be consumed with fats. 

Where are macronutrients on a nutrition label?

Finding macronutrients on a nutrition facts panel is simple because they’re in bold font. Calories are listed by serving size at the very top of the panel. 

Total fat is listed next, in bold, and is broken down into categories: saturated fat (bad in excess), trans fat (bad in any amount), monounsaturated fat and polyunsaturated fat (both good for you). 

Carbohydrates are the next macronutrient listed, also broken down into dietary fiber (the more the better), total sugars (stay under 9 grams/serving)  and added sugars (minimize whenever possible). 

Finally, protein is listed at the bottom and has no sub-categories.

Remember that not all macronutrients are created equal:

• For carbohydrates, this means sources high in fiber (14g fiber per 1,000 calories), with minimal processing, are preferable. Think whole grains, non-starchy vegetables (e.g., broccoli), whole fruits and dairy products without added sugars. 

• Protein should be consumed evenly throughout the day, including pre- and post-workout meals. High-quality proteins such as chicken, fish, turkey, eggs and legumes are the best choices.

• Fats from olive and peanut oils, avocados, nuts, sunflower and flaxseeds and fish oil are all great options.

In summary, consuming high-quality, nutrient-dense foods at regular intervals throughout the day is crucial to health and well-being, as well as optimal performance. 

Risks of undernutrition

Athletes run a higher risk of becoming undernourished, whether that’s through not consuming enough calories overall or not consuming the right amount of each macronutrient. Undernourishment can lead to:

• Performance worsening with too little food/not enough carbs
• Inability to sustain prolonged vigorous exercise (directly related to initial levels of muscle glycogen)
• Immune system dysfunction
• Vitamin deficiency: vitamins A, D, E and K need fat to be utilized by the body
• Decreased BMR: a decrease in sympathetic nervous system activity, decreased hormone production, decreased cell regeneration

Understanding your caloric requirements, your activity’s macronutrient requirements and making sure you’re meeting them with nutrient-dense foods is critical to peak performance. 

Key takeaways

To get to peak performance, it’s vital to be nourished with nutrient-dense foods that are tailored to your activities. Calculating your caloric needs can be done by multiplying BMR by physical activity level (PAL). Calculating macronutrient ranges is the most effective way to optimize your workout, but keep in mind that these numbers will be in flux. To get to the best starting point, utilize the dietary recommendation on macronutrient percentages and further zero in on carb, protein and fat intake by considering activity goal and intensity level.  Changing any eating pattern can be tricky, but the key is to give yourself the time to adapt, observe and make small changes — and, most importantly, listen to your body.