Studies of the diets of ethnic groups that have a low incidence of acne form the basis of most of the acne diets. Studies of the diets of tribes in New Guinea, Paraguay, and the Bantu of South Africa, all of whom have little or no acne, show that they eat a primarily plant-based diet. Similarly, in other countries where the diet is plant-based such as Japan, there is a relatively low occurrence of acne.

Studies have shown that half of acne patients tested had abnormal glucose levels, and in another study, 80%of premenstrual women with acne had abnormal glucose metabolism These data and others that show a high carbohydrate diet increases the levels of testosterone in the blood of both men and women, have lead to the recommendation of reducing the amount high carbohydrate foods or foods containing high levels of refined sugar to treat acne.

Researchers have developed a method for measuring how quickly carbohydrates are converted into glucose. The more rapidly a food is converted to glucose, the higher the level of insulin is secreted into the blood. The scale is called the glycemic index. Eating lower glycemic index foods may help reduce the number and severity of acne breakouts.

A large study of over 45,000 nurses found a link between the amount of dairy products these women consumed and the severity of acne they experienced. Women who reported consuming higher amounts of dairy products reported more severe acne. Similarly, the two ethnic groups with little or no acne also consumed no dairy products.

Several studies have compared the results of zinc supplementation with oral antibiotic therapy to resolved acne and found zinc to be almost as effective as the antibiotic tetracycline.

Opinions vary in the medical community as to whether or not diet plays a significant role in acne. Some common misconceptions about the connection between food and acne breakouts have been disproved. For example, according to several studies, chocolate does not cause acne.. Acne is caused when glands in the skin called sebaceous glands begin to form sticky oil called sebum. These glands are stimulated by hormones that become active at puberty which is why acne occurs most often in adolescence when these hormones are produced in abundance. The oils formed by the sebaceous glands hold dead skin cells preventing them form being sloughed off. As these cells die, they create the perfect environment for bacteria to grow. When these bacteria called Acne Vulgaris become too plentiful, they will attempt to erupt from the skin causing a pimple. Sometimes, when the bacteria grow, the body sends white blood cells to fight the infection. This natural reaction can cause painful, large cysts to form in the deeper layers of skin. Chocolate may not cause acne, but the fat and sugar that usually accompanies chocolate may.

Eliminating certain foods from the diet and increasing the amount of specific vitamins and minerals may help reduce the amount of sebum produced and prevent acne breakouts. However, the interaction between diet and acne is not a simple cause and effect relationship. If an oily food is eaten, the oil does not travel to the skin or cause it to be oily, but high levels of fat in the blood may effect the production of hormones such as testosterone. Higher levels of hormones may cause acne to worsen.

Many high carbohydrate foods are believed to worsen acne. Researchers have discovered that high carbohydrate foods increase the levels of insulin in the blood. High levels of insulin can raise hormone levels in the blood.

Researchers recognize that not all carbohydrates are bad. Some carbohydrates digest more slowly than others, causing a gradual rise in blood sugar after eating. Researchers have developed a glycemic index to rank carbohydrates and other foods according to the effect they have on blood sugar.

The glycemic index is a scale of 0–100. Foods with higher glycemic index ratings break down quickly and cause a sharp spike in blood sugar. When blood sugar rises quickly, the body produces a surge of insulin to lower the amount of glucose in the blood. Insulin is a hormone that helps the body take sugar (glucose) out of the bloodstream and put it into cells, where it can be used for energy or stored in fat. Foods with lower glycemic index ratings break down more slowly. They cause a more gradual rise in blood sugar, which means less insulin will be needed.

Foods that have a high glycemic index rating include: white bread, white rice, white potatoes depending on how they are cooked, beer, corn products and some products containing refined sugars. Foods with moderate glycemic index ratings include: whole grain breads and pastas, brown rice, sweet potatoes, green peas, many fruits (especially when eaten alone) and yogurt. Many of these foods are on the list of foods to avoid in the acne diet.

Low glycemic index or no GI foods include: rye grain, nuts, legumes such as black beans and lentils, green vegetables, apricots, and cherries. These foods may be enjoyed an may not worsen acne.

Foods that are high in fiber tend to have lower glycemic index numbers, because fiber takes longer to digest. Studies have shown that the presence of other foods such as fats like olive oil, can also slow digestion and keep blood sugar from rising too quickly. The glycemic index can be used along with the acne diet, to help choose which carbohydrates can be eaten with the least effect on blood sugar.

Definition

The acne diet or more accurately, the acne-free diet, is simply a way of eating claims to improves or eliminates acne. There is some debate in the medical community about the impact of diet on acne; however, there is a body of evidence to support the idea that what is eaten may affect the skin.

By reviewing research from over 40 years, doctors such as dermatologist, Dean Goodless have developed a set of recommendations regarding foods that may prevent acne. In his book The Acne-Free Diet Plan, Dr. Goodless presents his recommendations. He suggests eating a diet low in fat and high in fiber along with avoiding peanut product, fried foods, excessive salt, dairy products, foods that are high in refined sugars, and high carbohydrate foods.