Gluten intolerance? 🙂
More seriously, I’m on tablets that boost insulin production, they really help pile on the pounds if I’m not careful, I have a tricky a tricky balance of food intake, activity and tablet dose and it all changes with the time of year and temperature. I’ll put on weight more easily when it’s cold and I’m less active than over the summer when it’s warm.
Carbohydrate control is a huge dietary factor. I can eat more carbs over summer as I’ll burn them off, over winter I’ll tend to cut back on the carbs or the extra insulin the tablets produce just stick the carbs straight on as fat.
Without suggesting that you have any odd metabolic issues like mine, ask yourself:
Have you really had the same levels of activity over winter?
Has your diet really stayed the same?
If you can certainly say yes to both, might be worth cutting back on the carb content of meals a little and seeing what happens.