Gels are defined as biphasic colloidal systems: a liquid phase embedded in a solid phase.
Energy gels can be considered as a concentrated source of carbohydrates. The latter must be both simple and complex carbohydrates, to give the body available energy both in the short and medium term. The speed difference in the energy supply lies in its structure: the simple ones consist of single or maximum a double sugar and provide energy in the form of glucose (dextrose) in the bloodstream in a short time as they are rapidly absorbed. Complex sugars are instead longer chains of sugar joined together and, consequently, the absorption time is longer. In addition, the simultaneous intake of different types of carbohydrates accelerates the intestinal absorption of these carbohydrates because they take advantage of different entrance ports within the bloodstream (Currell & Jeukendrup, Med Sci Sports Exerc, 2008). The complex glucose combination of simple sugars and complex carbohydrates allows the body to supply energy as soon as a few moments after taking it for up to a couple of hours later (depending on the exercise exerted and the person’s characteristics). Additionally, some useful molecules may be added to the energy gels. An example of this is Branch-chained Amino Acids (BCAAs): BCAAs (in particular L-isoleucine and L-valine) can be a source of parallel or alternative energy to carbohydrates, in particular conditions such as fasting or particularly intense and protracted efforts over time. This is very useful, for example, during workouts and during ultra-long trials. In addition, BCAAs act at the level of the nervous system by alleviating the sense of perceived fatigue (Newsholme & Blomstrand, J Nutr, 2006). The gels can also contain caffeine, which through researched biochemical mechanisms enhances the effect of adrenaline and noradrenaline neurotransmitters, increases basal metabolism and fat metabolism, and reduces symptoms of fatigue (Meeusen et al, Nestle Nutr Inst Workshop Ser, 2013).