There is a growing body of scientific evidence to support the idea that diet and acne may be, at least in part, connected. Perhaps the most overlooked dietary factor that may affect acne development is a person’s caloric intake.
Research has shown that a high calorie diet affects hormones that are associated with acne, hypothetically leading to more acne. On the flip side, lowering calories might have the opposite effect.
So when people eliminate foods they heard were bad for acne, their acne may improve, and they may give credit to the "acne diet" they are on for their clearer skin, when in fact, they are simply inadvertently reducing their total calorie intake.
However, the science is not yet conclusive on this topic. Whether or not increased calories directly cause acne, and whether reduced calories could help clear up acne is still up for debate and will require further research.
Let's have a look at how calories affect hormones in the body, specifically insulin, and how this might be associated with acne.
Warning: Deep science ahead! (but it's kinda interesting actually).
Acne and Insulin Hormones
Researchers have associated three insulin hormones with acne development. These hormones include insulin, insulin growth factor 1 (IGF1), and IGF1 binding factor (IGFBP-1). Researchers have identified that the connection between insulin hormones and acne is due to the action of two proteins called FoxO1 and mTORC1. FoxO1 acts to suppress skin oil production and mTORC1 acts to promote skin oil production. Researchers have found insulin acts by decreasing the amount of FoxO1 and increasing the amount of mTORC1 in the body. When FoxO1 levels are decreased and mTORC1 levels are increased, this leads to a large increase in skin oil production that likely plays a role in acne development.3
In support of these findings, a 2016 study compared the IGF-1, FoxO1, and mTORC1 levels in acne and healthy patients. The researchers found that acne patients had higher IGF-1 and mTORC1 levels compared to healthy patients.4
Caloric Intake and Insulin Hormones
As scientists believe that insulin level changes may lead to acne development, researchers have begun investigating whether a person’s caloric intake affects the level of insulin, insulin growth factor 1 (IGF-1), and IGF1 binding factor (IGFBP-1).
Two studies have been performed in order to better understand the connection between high caloric diets and insulin hormone levels. After completing the studies the scientists ultimately concluded that patients consuming the low-calorie diets had decreased blood insulin levels and an increase IGFBP-1 levels, which acts by binding to IGF-1 in the blood. With these findings, scientists believe that consuming a high-calorie diet will lead to greater insulin and IGF-1 levels, which then causes a decrease in FoxO1 and an increase in mTORC1. Decreased Fox01 and increased mTORC1 would lead to more skin oil production that could potentially lead to acne development.2
Extreme Low-calorie Diets Result in Less Sebum Production
Going extremely low on calories is, of course, not a sustainable way to live. However, two studies done in 1970 and 1972 showed that severe caloric restriction decreased skin oil secretion dramatically. This is interesting from a scientific standpoint since increased skin oil production is directly related to acne. If fasting creates significantly less skin oil, would excess calorie consumption create significantly more skin oil? This remains to be seen.
The first study, performed in 1970, looked at the response of the sebaceous (skin oil-producing) glands to caloric restriction in 18 overweight patients for 4 to 8 weeks. They found an average decrease of sebum production of 40%.5
The second study, performed in 1972, followed 4 patients who fasted for 10 days. After 5 days of fasting, all fats in the skin oil on the forehead were reduced, except for a type of fat called squalene. When normal diet was resumed, the change reversed.6
The Bottom Line
When it comes to diet and acne, one of the most overlooked variables is calorie consumption. Lower calories may temporarily decrease acne and higher calories may temporarily increase acne. Therefore, when people remove "bad" foods from their diet in an attempt to help with their acne, they might see a temporary reduction in acne and believe it is due to eliminating those "bad" foods, when in fact, it is simply that by eliminating those foods the person reduced his calorie intake.
While a potential link exists between caloric intake, insulin levels, and skin oil production, more research is needed to determine if low-calorie diets would actually clear acne. In the meantime, rather than eating an extreme diet of very low calories, eating sensible portions of nutritious, low glycemic foods will contribute towards keeping both your body and skin healthy and in good condition.