I think of feeder insects as "vessels" for nutrients to be delivered to your animals. If that vessel is lacking nutrients or has nutritional imbalances it delivers that to the animal eating  it. If reptiles & amphibians are being fed the same diet every feeding that has nutritional gaps, the animals overall health will start to decline and develop nutritional deficiencies resulting in illness and sometimes even death if not treated. A great example of this is the ever so common House Crickets that are often thought of as “staples” as feeder insects for pets. Crickets have a higher Phosphorus to Calcium ratio making it unbalanced and in turn causes the consumer (the reptile/amphibian) to have to use more calcium to metabolize this Phosphorus to Calcium ratio imbalance. This results in your animal actually “losing” calcium from consistently eating a calcium negative food source as opposed to gaining calcium for the body to absorb to be able to function properly. Over time the animals' calcium stores will deplete and this leads to what is called Metabolic Bone Disease (which oftentimes is irreversible if left too late and can result in an incredibly painful death). 

That is just one example of nutritional deficiencies. This is commonly seen in captivity and not in the wild because in captivity we tend to have very limited access to variety in terms of different feeder insects species. This is different than in the wild because reptiles & amphibians have access to all sorts of insect variety and each insect has different levels of nutrients within them. The more variety the animal eats, the more opportunity it has to “fill” these nutritional gaps that come from eating only one or two types of bugs that lack certain types of nutrients. For example, while crickets may have a “improper” Calcium to Phosphorus ratio, Soldier Fly Larva have a higher Calcium to Phosphorus ratio making them an ideal source for calcium as opposed to crickets. Gutload works to prevent nutritional imbalances by offering the feeder animals an ideal balanced diet packed with all essential vitamins, amino acids, minerals and just overall nutrition to “correct” these imbalances before being delivered to your pet. Keeping in mind a lot of nutrients are absorbed by the bugs themselves so this is why we wait 48 hours after offering the gutload to ensure the insects have had plenty of time to eat as much of the gutload as possible.

 The Super Greens gutload has been a big success for not only keeping feeder insects alive & healthy but they thrive on this diet, but mainly it hugely benefits the animal being fed the bugs being raised on this diet.