Human growth hormone (HGH) is an important hormone produced by the pituitary gland.
All carbohydrates increase your blood sugar and elevate your energy level. Since complex carbohydrates take longer to digest, they increase blood sugar over a longer period of time. You can tell whether or not it is a simple carbohydrate by its Glycemic Index Number. The higher the GI, the faster it will raise your blood sugar. Low GI Foods, or complex carbohydrates, allow for sustained energy as the sugar your body needs to operate is transferred into the blood. Because the sugars are released more slowly, they can be utilized as fuel over an extended period of time.
Simple carbohydrates break down very rapidly. This causes insulin levels to spike. Growth hormone levels increase significantly when insulin levels are low. More precisely, growth hormone inhibition is not caused by high insulin levels but rather high blood sugar. This is because insulin is secreted to bring down blood sugar levels. Consequently, during the day when food is consumed intermittently, growth hormone secretion by the pituitary is suppressed, and insulin release by the pancreas is increased.
This means that by consuming a large amount of high glycemic carbohydrates by themselves, it could completely halt the release of growth hormone.
Generally, a high carbohydrate, low-fat diet is absolutely devastating to growth hormone levels. This is one of the reasons why many people trying to lose weight on such a diet plateau after a period of time. Their inability to continue to lose weight is partly due to suppressed growth hormone levels.
A study comparing a group of boys consuming meals composed of high GI foods versus low GI foods found there were higher levels of the hormones insulin, noradrenaline, and cortisol after the high-GI meals. So a rapid rise in blood sugar and insulin can lead to a rise in cortisol, with its accompanying catabolic and lipogenic properties.
We need insulin, however, to promote the benefits of growth hormone. Studies show that GH fails to promote growth in animals lacking a pancreas, and it also fails if carbohydrates are completely restricted from the diet. The reason for this is that a strict low carbohydrate diet leads to chronically low insulin levels, and insulin is needed to drive amino acids into the muscle cells.
Moreover, Insulin-Like Growth Factor-1 is produced in the body through the combined actions of GH and insulin. And IGF-1 is at least as powerful an anabolic agent as either of its parents. But a low carbohydrate diet would lead to a reduction in IGF-1 levels. So a low carbohydrate diet is not the answer either. In fact, this relationship of insulin, growth hormone, and IGF-1 is one reason why those following a low carbohydrate diet also plateau after a period of time. There needs to be a period of carbohydrate consumption to reset the metabolism and hormones. It’s why I suggest a two-week normalization period between bulking and cutting.
There is a relationship with thyroid hormone here as well. Raising growth hormone levels has a profound effect on normalizing thyroid function. Studies also show that diets that continuously restrict carbohydrates, like the ketogenic diet, for instance, cause a reduction in the conversion of T4 to T3 and that administering carbohydrates can restore higher T3 levels after they have declined. This reduction in T3 is another reason people will plateau on low carbohydrate diets.
Adding to this is The American Physicians’ Association finding that fibers in vegetables, whole grains, and some fruits keep sugars in the intestinal tract for longer periods. This increases your blood glucose level more gradually than if you ate a simple sugar. So, fiber consumption would help to stabilize blood sugar, thus further enhancing growth release. So an ideal growth hormone enhancing diet would include some carbohydrates, but not an excessive amount. And the focus would be on low glycemic carbohydrates, which are mainly vegetables, fruits, and whole grains.