Off-season or the time after the completion of an important race (Ironman) can be an excuse for athletes to eat as much and whatever they want. I did it, too. Did it help? No, not really. Yes, I enjoyed being lazy and “unstructured” with my diet. I ended up putting on too much weight,though, which took me months to lose again.
Gaining weight isn’t necessarily a bad thing as long as it is kept within manageable limits. It is perfectly fine to put on a couple of extra pounds during a resting period.
Athletes will lose some fitness (power, endurance, strength), too. That is normal!
Remember that a rested body is able to absorb the right training stimuli just like a sponge.
I have learned, if I kept my body weight within a reasonable range I would find it a lot easier to get back into training and running particularly.
The bottom line is that a period of rest and weight-management can boost base training performance (reduced risk of (overuse)-injuries …) and your race results in 2016.