How is your sleep? Caffeine intake? Stress?
Weight gain especially around the middle is more an overload of stress (or under recovery lifestyle)....which can come from excess exercise (especially increasing endurance), not eating enough, high stress lifestyle, lack of real sleep....etc. Many factors.
You will need to dial in nutrition around your workouts to make sure you can recover and do not promote excess cortisol output (esp with increased inflammation). Also need to make sure you are getting enough sleep...as that is the most important activity for recovery.
High inflammation will also lead to more cortisol output, so also make sure to take some fish oil.
Might want to take a week at lower intensity to let the body start to heal and recover, and then judge what happens next. Personally I would also cycle the carbs....go low for a few days and then up it for a day or so (and stick to real food carbs such as sweet potatoes, not bread and cereal). Helps to reset Leptin levels which do have metabolic influences (as carb refeeds are what reset them, not prot/fat refeeds).