Nutrition is a key component of any training program. Without the proper nutrients, the body won’t be able to recover from exercise, and no progress will be made. However, many nutritional profiles, especially in the West, over-rely on simple carbohydrates and subsequently neglect other important nutrients like fiber and diverse proteins. While carbs are important, they aren’t the entire picture when it comes to nutrition and training.
Carbohydrates are a preferred source of energy in the body(1). When ingested, carbohydrates are broken down by enzymes into simple sugars, like glucose. The pancreas releases insulin, a hormone that creates a number of different metabolic changes. Importantly, insulin maintains blood glucose levels by increasing the uptake of glucose into tissue, particularly the liver and muscles(1). Both the liver and muscles store this glucose as glycogen, which is basically a bunch of glucose molecules attached to one another. These glycogen molecules can then be easily accessed when the body needs a quick energy source. Glycogen is converted into ATP during glycolysis, and the ATP formed during that reaction is used to power muscular contractions for movement.
Carbohydrates, can be used positively in a training context if used properly. In particular, carbohydrate ingestion and timing can play an important role in endurance exercise, when your muscles can expend all of the stored glycogen. Particularly in the morning, when your body is in a fasted state, your glycogen stores are likely to be depleted(2). Studies have found performance improvements with appropriate carbohydrate timing and usage. As a game wears on and muscle glycogen stores decrease, carbohydrate intake can provide more glycogen to be converted into ATP. One study found that participants given a carbohydrate solution throughout a period of sprint intervals decreased muscle glycogen utilization, compared to a control group receiving fluids with no carbs(3).
For those of us exercising on multiple days per week, restoring glycogen levels following exercise is also an important consideration. A 2016 study looked into the effect of carbohydrates on fatigue when training multiple times in one day. The training consisted of two moderate intensity runs to complete exhaustion, separated by a four-hour rest period. The subjects in the group given a solution high in carbohydrates saw longer distances run in the second trial compared to a group with a low carbohydrate solution(4). Recent studies have even suggested there may be a connection between muscle glycogen stores and muscular electrolyte levels, which could play a role in fatigue(5). The interplay between carbohydrate intake, muscle glycogen levels, exercise fatigue, and recovery is complex but can be used to an athlete’s advantage.
All of the above scenarios are very particular. Specific carbohydrates timed perfectly around well-programmed training. Anyone who isn’t Tom Brady or an Olympic athlete probably doesn’t have the support staff to perfectly balance their simple sugar intake. Most people already ingest too much sugar, and that can have negative impacts on training
Probably the most well-known downside of bingeing on excess carbs is the dreaded crash. This is a result of the interplay between ingested carbohydrates and insulin discussed above. If you ingest a sleeve of Oreos before training, your body reacts by producing a massive amount of insulin via the pancreas. The insulin does its job and lowers blood sugar, but the level of the response can lead to extremely low blood sugar immediately following, a state known as hypoglycemia(2). The experience of hypoglycemia can include fatigue, faintness, and a lack of mental focus and clarity. Not the best way to start off a training session.
A sugar-heavy diet will always wreak havoc on insulin production, as your body is constantly reacting to massive spikes in blood sugar with insulin production and carbohydrate storage. Consistent insulin activity without management can lead to a condition known as insulin insensitivity. The molecules responsible for reacting to insulin and increasing sugar uptake stop reacting as strongly to insulin. The chronic energy surplus provided by carbohydrate-heavy diets increases the likelihood of insulin insensitivity. Disrupting this pathway can lead to increased fat deposition, as well as interrupting the process of muscular glycogen storage, which causes fatigue and a lack of recovery from exercise(6).
Considering carbohydrate balance can be tricky, other nutritional focuses should come into play. First, a balanced diet is always the most important nutritional foundation. That way, your body won’t have to deal with massive spikes in blood sugar, as you’ll always be fully fueled. Around 96% of American adults miss their daily requirement of fiber, and yet studies have shown that fiber intake (The Greens Party has 2g per serving) has a direct relationship with insulin resistance and fat deposition around the waist(7). Consuming more complex carbs and fiber sources lowers the glycemic index of simple sugars that are consumed alongside them, lowering the body’s insulin reaction and decreasing the likelihood of insulin resistance developing.
Further, amino acids, from whey protein and collagen have been shown to be an important fuel source while training for muscle growth. The combination of muscular contractions during exercise and presence of amino acids in the bloodstream creates an increased state of muscle protein synthesis in skeletal muscle. The key amino acid for this process is leucine, which is abundant in whey protein. Other proteins, like soy, lack leucine in the levels found in whey protein, but create the same stimulus for muscle protein synthesis when combined with an isolated leucine supplement(8). Combining well-rounded nutrition with timely protein supplementation can provide the energy and protein synthesis you might be looking for with carbohydrates.
There are multiple considerations to make when fine tuning nutrition to match an exercise regimen. Depending on what the overall goals are, a different balance of macronutrients and micronutrients should be achieved. However, there always needs to be a solid foundation present. Overconsumption of refined sugars can disrupt the basic systems of energy balance in the body, creating a poor environment for fatigue management during training and recovery afterward. More focus given to simple, balanced nutrition daily and protein around training will give a boost to any training program.
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