Alan Thicke Was Picture of Health at Christmas Party

Alan Thicke went to a Christmas party at John Paul DeJoria's house on Sunday ... and people there say he was happy, healthy and looking forward to the holidays.

Alan, his wife, Tanya, and his son, Brennan, mingled with celebs like Smokey Robinson, Jane Seymour and Clint Eastwood at the Malibu shindig which had everything -- live band, petting zoo, photo booth, Santa Claus, real snow AND an In-N-Out truck.

When it came time to chow down, we're told Thicke ditched his burger bun and ate it with just lettuce. His pal Ron White was also there and tells us Alan was health conscious about his diet, and avoided carbs.