FitStart Guide
Nutrition Basics
-
Nutrition provides the body with the energy and nutrients needed to support everyday functions, physical activity, growth, and recovery.
-
Understanding nutrition starts with the basics, including calories, macronutrients, micronutrients, and the quality of the foods we eat.
-
The sections below break down these concepts and explain how different nutrients and types of food contribute to a balanced and informed approach to nutrition.
Menu
Calories
What Are Calories?
Calories are a measure of energy. In the nutritional world, this is often represented by “big” calories, also known as kcal or Cal on nutritional labels. Calories are used to provide the energy needed for basic life functions and tasks, such as cellular respiration or protein metabolism. This energy is then used appropriately depending on the body’s needs.
Caloric intake depends on both quantity and quality. Caloric quantity per person depends on various factors, including height, weight, age, gender, and exercise. Caloric quality is also crucial for maintaining good health. Although some foods may have the same amount of calories, their benefit and effect on the body may differ through nutrient, protein, fat, and similar differences. Too much intake of any food group creates an imbalance within the body.
By 2020, most large companies updated their nutritional labels, incorporating a larger font and display for calorie intake. When reading a nutritional label, calories per serving is shown, although this may not be your recommended intake [1] [15] [16] [19] [20].
What are Maintenance Calories?
Maintenance calories refers to the amount of calories necessary to maintain and sustain your current weight. Generally, the average male requires around 2,500 kcal per day, while the average female requires around 2,000 kcal per day. However, this number is not uniform for each individual, and your exact requirements depend greatly on age, weight, height, and exercise in addition to gender.
To maintain a healthy weight, there are various processes and steps you can take, such as counting calories and consuming a variety of healthy foods. Counting calories is not necessary all the time, but it can occasionally give you an approximate idea of your daily intake. To do this, check nutritional labels for Calories per serving and monitor your personal serving size throughout the day. Furthermore, consuming each food group and balancing your diet can ensure that proper nutrients are available to you [1] [15] [16] [19] [20].
What is a Calorie Surplus and a Calorie Deficit?
A calorie surplus means consuming more calories than your body typically burns. This forces the body to store excess calories as fat, contributing to weight gain. On the other hand, a calorie deficit means consuming fewer calories than your body typically burns, forcing the body to burn excess fat. This typically results in weight loss. Overall, to undergo weight loss or weight gain, a calorie deficit or surplus, respectively, may be helpful.
The clinical significance of caloric intake is tied to both physical and mental health. Obesity can lead to an increased risk of harmful effects on the body, including heart disease, high blood pressure, and increased risk of stroke, just to name a few. Beyond that, it can contribute to depression, low self-esteem, and an increased risk of being bullied, worsening these effects. Insufficient caloric intake is tied to similar mental health effects, and can hinder the normal functions of the body [1] [15] [16] [19] [20].
macronutrients
Protein is a vital macronutrient found in many food and drinks that we consume. Individual necessary intake varies based on personal calorie intake, weight, gender, age, and activity level. When food containing protein, such as salmon, egg, or meat, is consumed, the body’s digestive system breaks it down into its components, known as amino acids. This is part of your metabolism.
Proteins serve many important functions, helping to keep the body functioning and moving. Some notable actions proteins do include building new proteins, providing structure and support, breaking down nutrients, sending chemical signals, speeding up reactions through catalysts, and many more.
In terms of fitness, proteins are crucial for exercise, repair, and recovery. The amino acids work to repair micro-tears caused by exercise, allowing the muscle to grow back thicker and stronger. Furthermore, proteins can help enhance endurance, boost the immune system, and fuel recovery [3] [8] [21] [25].
Carbohydrates are also an essential part of the macronutrients, with a primary focus on energy and digestion. There are three main types of carbs, including sugars, which are simple carbs, as well as starches and fibers, which are complex carbs. The best practice is to eat plenty complex carbs, and to moderate simple carbs. This determines the food’s chemical structure and how quickly our bodies can digest it.
These macronutrients are also our body’s main source of fuel and energy. As carbohydrates are ingested, they are broken down by the digestive system into glucose, or blood sugar. Insulin then helps direct and convert carbohydrates into usable energy for cells.
Carbohydrates also play a huge role in fitness, specifically in terms of quick energy, intense sessions, recovery, and endurance. Carbohydrates are the only foods which can be broken down quick enough to provide energy during high-intensity exercise. Without them, the body burns through muscle and protein, relying on other sources of energy for exercise [2] [7] [10].
Fats are the third essential group of macronutrients. These are also known as lipids, and are essential to the body. There are different types of fats, and they range in terms of how beneficial they are for the body and how much should be consumed.
-
Saturated fats are the “mixed fats”, and they can raise your unhealthy cholesterol level. Therefore, they should be moderated.
-
Unsaturated fats are the “good fats”, and do not have the same negative effects as saturated fats. This is composed of both monounsaturated fats and polyunsaturated fats.
-
Trans fats are the “bad fats”, and they raise unhealthy cholesterol levels while decreasing good cholesterol levels. In general, you want to avoid these foods.
Fats have many purposes for both health and fitness. They provide energy for the body over extended periods of exercises, keep your skin and hair healthy through vitamins A, D, E, and K, and help with basic bodily functions [11] [13].
-
micronutrients
Vitamins
The micronutrients are made of two main categories: vitamins and minerals. Vitamins are a group of substances necessary for cell function, growth, and development. There are 13 essential vitamins, grouped into 2 categories: fat-soluble vitamins and water-soluble vitamins.
-
The fat-soluble vitamins include Vitamins A, D, E, and K.
-
Water-soluble vitamins include Vitamins C, B1, B2, B3, B5, B6, B7, B9, and B12.
Fat-soluble vitamins tend to dissolve in fat and accumulate in the body, while water-soluble vitamins dissolve in water, and are usually not stored in the body. Instead they are excreted with the sole exception of Vitamin B12, which is stored in the liver. Therefore, water-soluble vitamins should be consumed on a much more regular basis. Neither too little not too much intake of a vitamin is beneficial, and can lead to deficiencies or toxicity in incorrect amounts [5] [14].
mInerals
Minerals are the second group of micronutrients, and are the inorganic elements that are essential for normal bodily development, function, and structure. There are 2 main types of minerals: macrominerals and trace minerals.
-
Macrominerals are the major minerals that your body requires in larger amounts, including calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur.
-
Trace minerals are only required in small amounts, but are still crucial, including iron, manganese, copper, iodine, zinc, cobalt, fluoride, and selenium.
These nutrients help to keep your bones, heart, muscles, and brain working normally, maintaining homeostasis and providing support and structure across the body. Others are responsible for protection, cellular respiration, and the strengthening of the immune system. Overall, these minerals serve a multitude of functions and are essential for optimal health [12] [22].
Food Quality
They have been linked to a reduced risk for chronic disease, including heart disease, diabetes, and cancer. Whole foods may also elicit significant weight loss, and can help maintain your health [4] [18] [24].
Whole Foods
Whole foods refers to food that is consumed in or close to its natural state. This includes food without processing or with minimal processing and additives. Examples of whole foods includes fresh fruits and vegetables, whole grains, unprocessed meats, and nuts. When searching for whole foods, check the ingredient list. Select items that contain little to no unusual ingredients and includes around 100% of the desired product.
These foods provide many benefits, and retain all their natural fibers, vitamins, and minerals.
vs.
Processed Foods
Processed foods include any food that has been altered from its natural state. Some associations define it differently, but the general idea is that any form of washing, cleaning, packaging, heating, etc and any additives, preservatives, or flavors incorporated makes a food processed. In this way, many foods at the supermarket are processing to some degree.
Processing may be beneficial, and may make food safe for consumption, suitable for use, or longer lasting. Additionally, not all processed foods are bad and result in harm to bodily health. Therefore, foods have been broken into different severities, which determine the amount to which a food has been processed [6] [17] [23].
-
Unprocessed or minimally processed foods include whole foods, which are minimally altered and quite natural. This may include refrigerated or preserved natural foods.
-
Processed culinary ingredients include foods that are incorporated into dishes that stem from a minimally processed food, such as certain types of cooking oils.
-
Processed foods derive from the above groups, and may have added salt, sugar, or fat. The flavor and durability of these foods may have been altered
-
Ultra-processed foods go beyond regular measures, and incorporate artificial colors, flavors, or preservatives. They are often mass produced and ultra-cheap [6] [17] [23].
References
[1] Centers for Disease Control and Prevention. (2026b, March 27). Tips for maintaining healthy weight. https://www.cdc.gov/healthy-weight-growth/about/tips-for-balancing-food-activity.html
[2] Cleveland Clinic. (2024, March 8). Carbohydrates. https://my.clevelandclinic.org/health/articles/15416-carbohydrates
[3] Cleveland Clinic. (2025, June 24). Proteins. https://my.clevelandclinic.org/health/body/proteins
[4] Esquivel, M. K. (2022). Nutrition benefits and considerations for whole foods plant-based eating patterns. American Journal of Lifestyle Medicine, 16(3), 284–290. https://doi.org/10.1177/15598276221075992
[5] Harvard T.H. Chan School of Public Health. (2023a, March). Vitamins and minerals. The Nutrition Source. https://nutritionsource.hsph.harvard.edu/vitamins/
[6] Harvard T.H. Chan School of Public Health. (2023b, August). Processed foods and health. The Nutrition Source. https://nutritionsource.hsph.harvard.edu/processed-foods/
[7] Holesh, J. E., Aslam, S., & Martin, A. (2023, May 12). Physiology, carbohydrates. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK459280/
[8] Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., Purpura, M., Ziegenfuss, T. N., Ferrando, A. A., Arent, S. M., Smith-Ryan, A. E., Stout, J. R., Arciero, P. J., Ormsbee, M. J., Taylor, L. W., Wilborn, C. D., Kalman, D. S., Kreider, R. B., Willoughby, D. S., . . . Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Protein and Exercise. Journal of the International Society of Sports Nutrition, 14. https://doi.org/10.1186/s12970-017-0177-8
[10] Kanter, M. (2017). High-Quality carbohydrates and physical performance. Nutrition Today, 53(1), 35–39. https://doi.org/10.1097/nt.0000000000000238
[11] Lowery, L. M. (2004). Dietary Fat and Sports Nutrition: a primer. Journal of Sports Science and Medicine, 3(3), 106–117. https://pmc.ncbi.nlm.nih.gov/articles/PMC3905293/#sec1-2
[13] National Library of Medicine. (2024, July 24). Dietary fats explained. MedlinePlus. https://medlineplus.gov/ency/patientinstructions/000104.htm
[12] National Library of Medicine. (n.d.). Minerals. MedlinePlus. https://medlineplus.gov/minerals.html
[14] National Library of Medicine. (2025, January 21). Vitamins. MedlinePlus. https://medlineplus.gov/ency/article/002399.htm
[15] NHS. (n.d.). Calories and weight loss. nhs.uk. https://www.nhs.uk/better-health/lose-weight/calorie-counting/
[16] NHS. (2023a, April 17). Understanding calories. nhs.uk. https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/understanding-calories/
[17] NHS. (2023b, June 12). Processed foods. nhs.uk. https://www.nhs.uk/live-well/eat-well/how-to-eat-a-balanced-diet/what-are-processed-foods/
[18] NYC Health. (n.d.). Whole foods. https://www.nyc.gov/site/doh/health/health-topics/whole-foods.page
[19] Osilla, E. V., Safadi, A. O., & Sharma, S. (2022, September 12). Calories. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK499909/
[20] U.S. Food and Drug Administration. (2024, March 5). Calories on the Nutrition Facts Label. U.S. Department of Health And Human Services. https://www.fda.gov/food/nutrition-facts-label/calories-nutrition-facts-label
[21] Watford, M., & Wu, G. (2018). Protein. Advances in Nutrition, 9(5), 651–653. https://doi.org/10.1093/advances/nmy027
[22] Weyh, C., Krüger, K., Peeling, P., & Castell, L. (2022). The role of minerals in the optimal functioning of the immune system. Nutrients, 14(3), 644. https://doi.org/10.3390/nu14030644
[23] Yale School of Public Health. (2025, September). Ultra-processed foods information sheet. https://ysph.yale.edu/research/information-sheets/ultra-processed-foods/
[24] Yang, P., & Cohen, L. (2012, March 26). Whole foods or supplements? UT MD Anderson. https://www.mdanderson.org/cancerwise/whole-foods-or-supplements.h00-158749167.html
[25] Zhao, S., Zhang, H., Xu, Y., Li, J., Du, S., & Ning, Z. (2024). The Effect of protein intake on athletic Performance: A systematic review and meta-analysis. Frontiers in Nutrition, 11, 1455728. https://doi.org/10.3389/fnut.2024.1455728