By: Steve Born
Prefatory comments: The information in this article is something I've written about before. However, with the number of emails I continue to receive questioning Hammer Nutrition's use of maltodextrin in our fuels--primarily coming from athletes who are following a carb-restrictive diet, and convinced that it is some kind of "evil" substance--it's time to set the record straight again.
It takes more than just a quick internet search to understand why maltodextrin--when used at the right times (key point right there)--is actually the ideal fuel to use during exercise and immediately after.
With that said, let's start with the latter, post-exercise refueling...
When you finish an exercise session, two things are highly active for a relatively short period of time--one is an enzyme known as glycogen synthase and the other is insulin. Glycogen synthase is responsible for taking your carbohydrate intake and converting it into glycogen for storage in the muscles. You have depleted your bodily stores of glycogen, so it's crucial to "refill the tank" so that you have those stores replenished and ready for tomorrow's workout. Insulin, along with glycogen synthase, is what drives this glycogen into the muscle cells.
One reason why maltodextrin is ideal for post-workout carbohydrate replenishment is precisely because of its high glycemic index rating. With the activity of insulin and glycogen synthase only remaining at high levels for a very short time, a quick-acting carbohydrate source is not only ideal, it's quite necessary (think "striking while the iron is hot"). The quicker acting the carbohydrate source, the sooner you will kick-start the glycogen restoration process.
Additionally, complex carbohydrates like maltodextrin will match body fluid osmolality parameters in more calorie-dense solutions as compared to simple sugars like glucose, sucrose, and fructose. This simply means that you will be able to digest more calories--without any delay from entering and exiting the GI tract--with maltodextrin than you can with any one- or two-chain simple sugar.
The other time when a high glycemic index carbohydrate is ideal is during exercise, and it is for exact same reasons that it's the right choice for post-workout glycogen restorage. As mentioned before, the carbohydrate source in our fuels is maltodextrin, which is a high-glycemic index (GI) carbohydrate source so it will spike your blood sugar. That doesn't sound like a benefit, but this is EXACTLY what you want when you’re engaged in exercise. You don’t want your carbs to take forever to increase your blood sugar/energy levels; you want that energy quickly, and that’s what maltodextrin does. Its GI rating is the same as pure glucose (100) so it definitely increases blood sugar/energy levels quickly. What it doesn’t do, however—and you can’t say this about glucose, sucrose, fructose, and other short-chain carbohydrates/simple sugars—is drop those levels quickly or precipitously.
Sugar is more of a “flash and crash” type of energy, while maltodextrin—because it is MANY saccharide molecules weakly linked together—provides a “quick-acting, long-lasting” energy. Another great thing with maltodextrin, as mentioned earlier, is that your body is able to digest a greater amount of calories—with no delay from entry to exit of the digestive tract—and make them available for energy production. You can efficiently digest up to 3x more calories with maltodextrin than you can with any simple sugar, and that basically eliminates stomach distress issues.
As far as insulin is concerned, maltodextrin does elevate blood sugar levels very rapidly and will cause an insulin release. This is not a significant factor during exercise, however, as Dr. Bill Misner explains: "During exercise insulin release is inhibited because sympathetic nervous system hormones are released and, concurrently, exercise augments muscle uptake of glucose from exogenous intake accompanied by lower insulin levels and effects."
Basically, what Dr. Misner is saying is that because energy turnover is high, and with the release of specific central nervous system hormones, the body is able to deliver glucose to the muscles with less insulin.
IMPORTANT NOTE: Aside from just prior to exercise, during exercise, and immediately following exercise, we do not recommend consuming high-GI carbohydrates, including maltodextrin.
As far a restricting carb intake in general is concerned, we are not advocates of a low-carb diet for pretty much anyone, especially endurance athletes. Carbohydrates are the main source of fuel to produce energy, and it is our position that when we purposely cut back too much on our carbohydrate intake it can have a negative impact on performance. We understand that ketogenic diets, at least in the short term, are purportedly beneficial for losing weight; however, there has been an increase in studies that show that this diet is not a healthy practice. Check out these links:
https://www.sciencedaily.com/releas…/2018/…/180828085922.htm --- Study author Professor Maciej Banach, of the Medical University of Lodz, Poland, said: "We found that people who consumed a low carbohydrate diet were at greater risk of premature death. Risks were also increased for individual causes of death including coronary heart disease, stroke, and cancer. These diets should be avoided."
http://www.drmirkin.com/…/keto-diet-may-lead-to-diabetes.ht… --- Dr. Gabe Mirkin writes: “A keto diet may increase risk for developing diabetes by preventing your body from responding to insulin, presumably by causing fat to be deposited in the liver.”
As far as low-carb diets/low carb intake during exercise is concerned, at one site (https://www.trainingpeaks.com/…/why-athletes-need-carbohyd…/), Dr. Rick Kattouf states, "Many athletes avoid carbohydrates in an attempt to teach their body to burn fat as the major fuel source. The thinking has become that consuming carbohydrates and the ability to burn fat do not go together. The truth is that athletes can burn fat and consume carbohydrates. Always keep this statement in mind, 'Fat burns in the carbohydrate flame.' Not only do carbohydrates provide energy for working muscles, they also assist in enabling fat metabolism. In short, carbohydrates need to be present in order for fat to be utilized for energy." 
A good article that explains this in more detail can be found at https://www.jackkunkel.com/…/why-do-fats-burn-in-the-flam…/…
Research  has shown that when carbohydrate levels are low, a substance known as pyruvate—which is formed during glucose metabolism—is unable to perform its job in the process of creating energy using oxygen (i.e. cellular respiration). When pyruvate is unable to perform its tasks—which it can only do in the presence of carbohydrates—the body’s ability to use fat as a fuel source significantly slows down or halts altogether. This same research shows that without replenishment of adequate amounts of carbohydrates, the body will cannibalize specific amino acids (BCAAs, alanine) from muscle tissues, which not only slows down metabolism, it also causes excess production of fatigue-causing ammonia.
Perhaps the most compelling argument against low-carbohydrate diets comes courtesy of an excellent article by Dr. Mirkin . A key piece of the article reads:
Some people believe that if you restrict carbohydrates, you will teach your muscles to burn more fat and preserve their small store of sugar (Metabolism, 2016;65(3):100-10). That is correct, but burning more fat and less sugar for energy slows you down (Nutrients, 2014;6.7:2493-508). The limiting factor to how fast you can move over distance is the time it takes to move oxygen into muscles. Since sugar requires about 20 percent less oxygen than fat does to fuel your muscles, you need to slow down and have less power when your muscles burn fat rather than sugar.
 McArdle WD, Katch FI, Katch VL. Exercise Physiology Nutritional. Energy, and Human Performance seventh, edition. 2010
 “Low-Carbohydrate Diets Harm Athletic Performance” at http://www.drmirkin.com/…/lowcarbohydrate-diets-harm-athlet…
Despite all of the fanfare surrounding the keto diet, we remain 100% convinced that this particular diet, especially if used long term, DOES NOT enhance exercise performance. We remain equally convinced that carbohydrates are vitally important—they are the key component—when it comes to fueling your body during exercise, especially in regards to being able to use fat as an energy source most efficiently and effectively. We also believe that carbs are extremely important to consume (protein as well) after your exercise session has been completed. The carbs are needed to replenish the muscle cells and the liver with fuel, and the protein will provide the amino acids needed for muscle tissue repair and immune system support.