I'm intrigued by people who eat the mythical 2400 calories a day and don't gain weight.
I'm 43 and can gain weight on over 1400 calories a day. I can eat up to 150g carb, protein I can eat up to 100g and fats around 50g (more than that and I feel sick). I don't walk much (maybe hit 10k once or twice a week) but I go crazy in a spin class, and I swim moderately front crawl about 40 mins and do a couple of conditioning classes with weights and a little bit of HIIT and I do a couple of rounds on the gym machines gradually building up the weight, once a week. Do I just need to drastically do more exercise in order to eat more?