Nothing frustrates me more than hearing people say “carbs are your worst enemy,” especially in the very active and athletic population. While I do think carbohydrate restriction is necessary within the context of the modern American diet and especially in those with blood sugar issues, depending on the intensity and frequency of your training, you may need more carbs than you think. I truly find that people are overloaded with information that is often times contradictory, especially when it comes to the role of carbs, fats, and proteins in the diet. That’s why I decided with today’s post to try and explain the role of different macronutrients during different intensities and modes of activity. My hope is that after reading this, you will better understand the roles different energy sources play, both at rest and during exercise.
*Please remember that I am not a biochemist. If you want to dig deeper into substrate utilization during exercise, there are complete textbooks on the topics. This post is meant simply to serve as an introduction to the role of different macronutrients at rest and during training.
Let’s start with the most misunderstood macronutrient of them all, fat. Fat is the most energy dense of the macronutrients, with each gram adding up to about 9 calories. Our body uses fat for a lot of things (many of which I will not cover in this post). For the purposes of today, let’s focus on the role of fat during different levels of activity. At rest, stored fat will be our main producer of energy, especially if we are in the fasted state. This makes sense because fat takes a long time to be broken down and turned into energy (ATP). During exercise, the story is a bit different. At low intensities (mild walking), fat will still be our primary energy producer, as our demand for energy still isn’t too high. However, as the intensity increases to a more moderate level, we being to rely more on stored carbohydrates. Now, here is an important point- we only have so much stored carbohydrate in our muscles and liver and when these stores get depleted (such as during the running of a marathon or a long bout of very intense exercise), fats are then again called upon for energy production (fat in muscle and stored fat). So, if you’re a marathon runner or someone who engages in long-bouts of low-moderate intensity exercise, adding some high quality fat in the form of avocados, nuts, and olive oil to your diet can be extremely beneficial to improve your performance.
**Note- The other population who will benefit from increase far consumption is anyone struggling to manage their blood glucose. In addition to implementing an exercise routine, replacing high amounts of carbs with some beneficial fat is a good step towards controlling spikes in blood sugar. The key point here is to replace carbs with fat, don’t eat large amounts of both.
Everyone’s favorite! When it comes to physical performance during exercise, carbohydrates are the most-rapidly accessible form of energy. Compared to fats, carbohydrates are much more rapidly broken down to produce ATP. This is exactly why I think a moderate amount of stored carbohydrate is necessary for individuals who engage in high-intensity exercise such as HIIT training, CrossFit, anaerobic sports such as hockey, football, basketball, and power lifting. These activities place a massive demand on the body for rapid energy and oxygen. Thus, someone engaging in these activities on a chronically low-carb diet is likely to see some impairments in their performance. The best way to ensure proper replenishment of carbohydrates is to consume them post-workout. In this state, you’ve: 1) depleted your muscles (and potentially your liver) of glycogen and 2) created a state where blood glucose (from the carbs you eat) can be rapidly taken up by the muscles. This means you’re less likely to have a crazy blood sugar spike with the meal, this is a good thing! So I guess my take on carbs is that they certainly have a place in exercise performance, especially high-intensity exercise, but the issue is that individuals often take this to mean that crushing 4 pieces of pizza post-workout is a good idea. I would not suggest this. Lastly, I don’t believe eating carbs immediately before a workout is necessary unless: 1) you’re previous meal was very low in carbohydrates or 2) it’s been more than 15 hours since you’ve consumed carbohydrates. However, tis will vary from individual to individual, so be mindful of how you feel and use that to gauge your nutrient/meal timing.
**Here’s a trick that I find helpful (again, this is highly variable to take it as you please). I train in the morning, so I consume a moderate of carbs following my training. At lunch (3-4 hours later), I don’t eat a ton of carbs to avoid a blood sugar spike. When dinner rolls around, I’ll add some carbs back in to replenish my glycogen stores for the next morning.
Favorite Sources- Sweet potatoes, plantains, blueberries, coconut, bananas, apples.
In reality, I think protein is underappreciated. In the active population, I’ve seen recommendations as low as .8 gram of protein per kg of to bodyweight as high as 2.5 grams per kg of bodyweight. Proteins make up all of the tissues in our body and serve vital roles in immune function, bone strength maintenance and organization of enzymes (which are really just proteins). So, anyone who is active is going to have an increased protein demand. Now, some populations will require higher intakes based on the amount of microdamage that occurs as a result of the training stimulus. For example, Person X who does CrossFit 5 times a week will require a ton of protein while Person Y who goes to 3 Pilates classes will have a much lower need. Additionally, it’s important to realize that protein can be converted to glucose in the liver, making it useful as a secondary fuel source during high-intensity exercise. For those of you engaging in resistance training, protein synthesis (building of new proteins indicating growth and repair) has been shown to remain elevated for 24-49 hours post-workout, so don’t buy into all of the “anabolic window” claims.