A healthy diet does a body good inside and out, and a dermatologist at Baylor College of Medicine says that this especially true for the skin, but not in ways that most people think.

"Some people believe eating a greasy dinner or a chocolate bar will cause an acne break out overnight, but there is no scientific evidence that supports that a meal can trigger acne," said Dr. John Wolf, professor and chair of dermatology at BCM. "Diet affects overall health, which includes the skin, but the effects take time to appear."

A diet high in sugar and fat is bad for the body – including the skin, Wolf said. Foods high on the glycemic index, meaning foods high in carbohydrates and sugars, can create fluctuations in blood glucose and insulin levels.

"There is good evidence these fluctuations cause a rise in androgen levels. That leads to more oil production on the skin, which can result in more acne," he said. "I've read studies that follow people who transitioned from a traditional diet to a Western diet and that aggravated acne problems over time."

Wolf added that three recent studies have demonstrated a relationship between cow's milk and acne possibly due to the high hormone content of milk.

Foods that are considered healthy for the body will also benefit the skin, he said. For example, foods containing antioxidants are believed to fight free radicals that damage cells and accelerate the progression of illnesses.

Current studies are looking into whether resveratrol, a substance produced naturally by certain plants, fights free radicals.

"Resveratrol is found in dark colored foods such as grapes, blueberries and pomegranates," Wolf said. "These may help slow the signs of aging, in the body and on the skin. There is also evidence that resveratrol may help prevent skin cancer formation."

Wolf said eating healthy is a good lifestyle choice to help prevent many illnesses, but won't replace daily skin care.

"It is still important to properly clean and moisturize the skin," he said. "Most importantly, always wear sunscreen regardless of the weather."