From the Chattanooga Times Free Press
Q: I've always heard that you should lay out for short periods of time and get a base tan before spending any significant time in the sun so you don't burn. Is that true?
A: The simple answer is no. If you're going to be out in the sun, you will need to use a good sunscreen to prevent sunburn.
The concept of the "base" tan has been tested by numerous scientists and physicians, and the results have been the same. The base tan offers no protection again sunburn and can even lead to more problems. Some of the researchers on these studies have found that people who abide by the base-tan theory are more likely to engage in riskier behaviors like tanning without sunscreen or reapplying sunscreen less frequently because they feel their base tan is protecting them.