You’ve heard it a million times: fitness is not just about what you lift, but also about what you eat. Nutrition is a critical part of any physical endeavor. Nutrient partitioning is the key to getting maximum results from everything you eat.
Every time you eat something, your body will use the calories, proteins, carbohydrates, and fats that you ingest. They will either be used by muscles for fuel, or stored as fat. Nutrient partitioning is how your body chooses where the nutrients will go, and how they will be used. A nutrient that goes to muscle is being “partitioned” to muscle. The same is true for nutrients that contribute to fat gain. This partitioning can be manipulated for better results.
You probably know someone who never seems like they need to diet. This fortunate person can also eat whatever he wants and muscles just seem to sprout no matter what he does. He probably has ideal testosterone and cortisol levels, and his nervous system seems to have been calibrated just to make everyone envy his physique. He probably also has genetics that make nutrient partitioning a breeze. The good news is, even though you may not have won the genetic lottery, you can improve your ability to partition nutrients as well as anyone.
Nothing matters as much as insulin when it comes to nutrient partitioning. Insulin is a hormone with many jobs, but here’s the least you need to know when it comes to insulin and fat loss: if you have too much insulin in your body, the body will stop burning its stored fat. Your body could not function without insulin, but too much of it is detrimental. The primary culprit for insulin spikes is the carbohydrate.
When you eat a food containing carbohydrates – think of starchy carbohydrates for this discussion, not the carbohydrates in vegetables – the breakdown of the carbs releases sugar into the blood. Blood sugar is regulated by the release of insulin. High levels of blood sugar produce high levels of insulin, and, as discussed above, high levels of insulin prevent fat loss. The manipulation of carbohydrate intake (and the ensuing insulin release) is the key to effective nutrient partitioning.
Carbohydrates are fuel. If you’ve ever been on a low carb diet you may have lost fat, but you probably noticed a drop in strength as well, depending on how much time you spent in a carb-depleted state. If you ingest most of your carbs within an hour window before and after your workout, your body will use the resulting blood sugar for fuel and attack the fat in your body. You’ll have high energy for performance, and your insulin levels will quickly return to normal after the post-workout carbohydrates. This is nutrient partitioning in action.
Tracking your food intake is the best thing you can do to improve your nutrient partitioning. Unless you know how many grams of protein, carbs, and fats you consume each day (your macronutrient ratios), you won’t be able to make adjustments. These ratios can make or break your performance and physique.
A 2004 study in Sports Medicine found that, while there are exceptions, bodybuilders would do best by parsing daily caloric intake into 55-60% carbs, 25-30% protein, and 15-20% fat. By following these guidelines, nutrient partitioning would be optimal for goals. Obviously, in order to construct a macronutrient ratio for yourself, you must be willing to know how many calories you need in a day. Once you know that, you can make changes based on your results. You can use the macro nutrient calculator on our site to find a starting point for your body type, activity level and goals.
In a nutshell, anyone can improve their nutrient partitioning abilities. It is largely a matter of regulating insulin through carbohydrate manipulation (and carbohydrate timing, ingesting most of them in the periods before and after a workout), and then ensuring that you get an adequate amount of protein and fat while consuming your daily calories. If you are willing to pay attention, keep a food diary, and experiment, you will be able to make sure that your body treats food as a muscle-building fuel, not as a signal to flood your system with insulin that will work against your goals.