Exercise vs. Diet for weight loss during the holidays

We are well into the holiday diet advice season.  What to eat and not eat,  when,  how often, how much, columns are in every paper, magazine, and on a million online sites.  From my reading,  it seems that the food intake process is more important than exercise.  Being mindful of my diet will be more effective than clocking more time working out.  Or,  I will lose if I think I can exercise more to compensate for the typical holiday diet.  I just read that the average person gains 5-10 pounds from Thanksgiving to New Year's Day, and that even with dieting in the new year 1 of those pounds will never go away.  That is a disturbing thought.  Is that saying that a 30 yr old guy weighing 160 lbs. will weigh 190 at age 60 if nothing changes except he eats a typical holiday diet every December?  I wonder about that.