Carbohydrates are at the center of fitness industry debate. Popular 21st century diet programs portray carbohydrates as intolerable and bad for body composition, while athletes, doctors, and USDA governing officials praise carbohydrates for their role in energy metabolism and overall health and well-being. Left and right wing nutritional extremist’s exhibit close-minded dietary philosophies that either completely shun or gluttonize carbohydrate consumption. In today’s industry, there is no in-between. As a result, fitness enthusiasts struggle to make sense of and practically apply carbohydrate intake guidelines and bounce back and forth between extreme views. Truth is, carbohydrates are not the innately evil fat-building macro nutrient monsters that most claim them to be. An open-minded, physiology-based nutritional approach can help to set the "carbohydrate and aesthetics" record straight.
Digestion, Absorption, and Delivery
Ingested carbohydrates are broken down into simple sugars (glucose, fructose, and galactose) within the gastrointestinal tract. With sodium’s help, these molecules absorb through the small intestine and circulate the blood stream (Gleeson & Jeukendrup, 2010). The liver converts all simple sugars into glucose molecules and stores glucose in the liver or muscle as glycogen. The liver serves to regulate blood glucose levels and fuel the central nervous system. Muscle glycogen is limited to use in energy metabolism within its stored muscle fiber and cannot reenter blood circulation (Gleeson & Jeukendrup, 2010).
Muscles use a mixture of glucose (carbohydrates) and triacylglycerol’s (fats) to foster energy for contraction (Gleeson & Jeukendrup, 2010). Exercise intensity determines the ratio of carbohydrate to fat utilization within an exercising muscle cell, while training volume AND intensity dictate carbohydrate storage depletion (Baechle & Earle, 2008). As you will read later on, understanding carbohydrate depletion is important for determining intake for repletion when maximizing aesthetics.
- Ex: If you run for 30 minutes at 40% of your VO2 max (a relatively low exercise intensity), you may burn 300 calories. Because both your exercise duration and intensity are short, you will not deplete a large percentage of your muscle’s glycogen stores. In this case, increasing either exercise intensity or duration will result in greater muscle glycogen depletion.
- Ex: Consequently, if you interval train for 30 minutes at an average of 80% of your VO2 max (a high exercise intensity), you may burn 500 total calories. Because you are exercising at a high intensity, you will deplete a larger percentage of your exercising muscle’s glycogen stores. In this case, exercise intensity determines glycogen depletion.
Fat requires oxygen for breakdown, while carbohydrates do not. Complete fat oxidation is, however, carbohydrate dependent. That is, carbohydrate breakdown byproducts must exist for fat oxidation to occur. At rest and during lower exercise intensities, muscles prefer fats over carbohydrates. As exercise intensity increases, however, muscles favor carbohydrates to fats. The fat burning process is oxygen dependent with longer and more detailed processes, while carbohydrate burning is quicker and less involved. Thus, carbohydrates are more readily available than fats for energy production during sudden and higher intensity exercise activities.
- Ex: If you sprint 400m from a standstill, your body will burn more carbohydrates than fat based on its need for immediate energy. Quick and powerful carbohydrate burning pathways fuel your body with enough energy to complete the sprint. Fat burning aerobic pathways cannot keep up with the energy production demands during high intensity anaerobic exercise.
- Ex: During a longer and slower 5 mile run, your body will prefer burning fats to carbohydrates. Lengthy, power restrictive, yet extremely efficient fat oxidation properties fuel your body with enough energy to complete the run.
The Fate of Ingested Carbohydrates
Various research studies indicate that 90-95% of all macro nutrients absorb (Brown & Chandler, 2013). Consequently, a high percentage of ingested carbohydrates function to serve a purpose- glycogen replenishment, MPS stimulation, fat storage, etc. Once liver and muscle glycogen stores are full, excess glucose molecules are deposited as fat. Carbohydrates delicate role in optimizing body composition can make determining consumption needs difficult. Ingesting too few carbohydrates may compromise weight room performance, while consuming too many may deter overall leanness (Brown & Chandler, 2013). Ultimately, your carbohydrate intake is relative to your metabolic efficiency, your total daily energy expenditure, and your training goal.
Practical Carbohydrate Intake Guidelines
Maximizing body composition requires a metabolic-specific macro nutrient intake. Your body's ability to grow, recover, and minimize fat storage varies tremendously from you to the next guy. Quantity is key. Eating carbohydrates in the right amounts will result in goal acquisition and long term aesthetics success. Stick to the numbers!
- Start by calculating your body’s total daily energy expenditure (TDEE). You can estimate this value quickly by using an online TDEE calculator.
- Create a slight caloric surplus if you intend to gain muscle or a slight deficit if you intend to reduce body fat (ex: 100-500 calories above or below, to start)
- Once your caloric intake is set, establish a carbohydrate percentage value (the percentage of your total calories that will come from carbohydrates). This value is dependent upon your training, metabolism, and goal.
- Bulking: use a slightly higher carbohydrate percentage (35-60%). Your metabolism and training status will determine where you fall within this range. If your body tends to process carbohydrates well (you eat a lot of carbohydrates and do not store a bunch of fat) AND your training regularly depletes glycogen stores, then stick to the higher end of the range. If your body does not process carbohydrates well AND your training does not regularly deplete glycogen stores, then stray towards the lower end of the range. “Classic bodybuilding training” (one large muscle group per day) does not regularly deplete systemic muscle glycogen stores.
- Leaning: use a slightly lower carbohydrate percentage (15-40%). See the “Bulking” bullet point above to gauge range rules.
- Multiply your total caloric intake value by your chosen carbohydrate percentage (in decimal form) to yield your total daily carbohydrate intake. Divide by 4 to convert from calories to grams (ex: 0.45 x 3000 = 1,350 carbohydrate calories, and 1,350 / 4 = 337.5g carbohydrate)
- Divide your daily total carbohydrate intake value by however many meals you plan on eating throughout the day to yield a net carbohydrate total in grams per meal, or use any of the advanced carbohydrate intake techniques listed below in the "additional tips" section to creatively distribute your carbohydrates throughout the day (ex: 337.5g / 6 meals = 56.25 grams per meal).
- Carb cycling- alternate between low, moderate, and high carbohydrate days throughout the week (not necessarily in that order). Carb cycling is a proven and tested body composition alteration method. Add carbohydrates to priority training days and subtract carbohydrates from non-priority days. You can carb cycle during both bulking and leaning phases. (Ex: If your primary goal is to develop a larger chest, then increase carbohydrate consumption during chest days).
- Nutrient timing- consume carbohydrates when your body can best use them. Intra and post workout carbohydrate consumption enhances muscle protein synthesis and replenishes glycogen stores. Increasing carbohydrates here means decreasing consumption in other meals. By bounding carbohydrate intake to your workout’s surrounding meals, you minimize fat storage opportunities throughout the day.
- The body is good at manufacturing glucose from non-carbohydrate sources. This process, termed gluconeogenesis, increases during periods of inadequate carbohydrate consumption to help regulate blood glucose levels and fuel the central nervous system. During periods of intense leaning or “contest prepping”, it is okay to dip down below daily recommended carbohydrate intake values (within reason). The human body is very adaptive and will find a way to maintain homeostasis. Don’t sweat it, temporarily.
- Glycemic index- measures the effect of carbohydrate intake on blood sugar levels. Meals containing simple sugars and lacking in fiber and healthy fats digest quickly and spike blood sugar levels. This phenomenon is optimal post workout and during long duration events (lasting in excess of 90 minutes). Consume meals lower in simple sugars and higher in complex carbohydrates, fiber, healthy fats, and protein at all other meals throughout the day to optimize the endocrine’s response to feeding.
- Carbohydrate absorption is sodium dependent. Most physique competitors cut sodium and increase carbohydrate feeding before a competition to “dry out” and “look full”. Since carbohydrates require sodium for transport across the intestinal wall, most competitors end up not benefitting from “day of” carbohydrate intake and look flat on stage. Do not completely attempt to eliminate sodium from your diet, period. Serious health complications can and will result.
- Avoid intolerances. Avoiding intolerable foods prevents systemic inflammation and optimizes gut health. An impaired GI tract can hinder nutrient absorption and negatively affect the metabolism. Gluten and lactose are common intolerances.
- Avoid "no carb" diets. "No carb" diets often yield immediate and rapid weight loss, and thus appeal to fat loss driven trainees. However, under such circumstances, weight loss is deceptive and does not truly reflect fat loss. Muscle glycogen draws water into muscle cells. Consequently, depleted glycogen stores reflect intramuscular water loss. That is, extreme carbohydrate restriction results in more water loss than fat loss.
- Consume an adequate amount of fiber. Fiber maintains intestinal health and moves waste through the colon. The small intestine is where macro nutrient absorption flourishes. Inadequate nutrient absorption can alter the metabolism and hinder goal progressions.
- Eat to fit your macros. As mentioned above, quantity is key. Hitting targeted macro nutrient numbers epitomize aesthetics success. With that said, some carbohydrate sources are more energy dense than others. For example, 100g of brown rice may provide 40g of carbohydrates, while 100g of broccoli may only yield 10g of carbohydrates. In this case, you must consume 400g of broccoli to reach the 40g of carbohydrates found in only 100g of brown rice. That is a lot of broccoli! Thus, low carbohydrate meal plan breakdowns may better suit lower energy dense options like fruits and vegetables, while high carbohydrate meal plan breakdowns support higher energy dense options like brown rice, yams, whole grain bread, and pasta.
Baechle, T. R., Earle, R. W. (2008). Essentials of strength and conditioning (3rd ED). Champaign, IL: Human Kinetics.
Brown, L., Chandler, T. (2013). Conditioning for strength and human performance (2nd ED). Philadelphia, PA: Lippincott Williams & Wilkins.
Gleeson, M., Jeukendrup, A. (2010). Sports nutrition: An introduction to energy production and performance (2nd ED) Champaign, IL: Human Kinetics.