groder wrote (see)
Thanks everyone
Just to clarify I am 40 years old, 5.5 tall and weigh 11 stone 10 pound.
Ok, so assuming you aren't a body builder, i'd say you probably are a stone or two heavier than you could be. I'm 6ft 1" and around 11 stone but I have the reverse problem to you. I struggle to prevent myself losing weight as my miles grow. This is not down to some magic metabolism I have or being "naturally thin" (no such thing exists) it's because I hate junk food and drink sensible enough levels of booze. I don't have a monster appetite so 3 "square meals" a day is usually enough for me (so I now force myself to graze on nuts and seeds to keep the weight on).
That's why I question whether you really do eat as healthily as you think. Even then, you may eat healthily but not low in calories. Nuts, seeds and oily fish are all fabulously good for you and definitely healthy food. They are all also extraordinarily high in calories. Healthy does not always mean low calorie.
The only sure-fire way to do it is to start to properly log approximate calorific values of all food and drink (including snacks of all types) and how much you should expect to burn off for a person of your size and then subtract the rough calories you are burning from exercise. If you are still in positive calories, do more and eat less/better. If you are in negative calories, you'll lose weight. If you are in negative calories and still gaining weight - your calculations are wrong so do even more and eat even less or do the maths work again
Good luck!