Sorry to say, tanning your backside at the beach won’t help you lose weight (unless you count complications from cancer).
Brown fat, also known as baby fat, acts more like muscle than fat. It helps babies regulate their body temperature by burning calories.
It had been thought that brown fat was present only in infants, but a study of 2,000 patients at the Joslin Diabetes Center found 7.5% of women and 3% of men retained some brown fat. And some goes a long way. Just 2.2 ounces of brown fat is capable of burning off 9 lbs. of white fat (the bad kind) a year!
The only downside: brown fat is only active in cold weather so technically I guess you can lose weight by going to the beach, you just have to go in the winter.