@ElTortilla Overweight MiL would go for a pub lunch Saturday, drink beer.
All in all they had a dreadful diet, cheap shop bought bread, cake, biscuits, fish and chips once a week, would sit and peel a satsuma and share it, no raw food, salad, fruit, fresh vegetables, tinned only, cheap meat,
nothing to give her vitality, mostly carbs, she was in the same situation as yourself, stiff and in pain.
Dietwise, try improving your energy levels, multivitamin with iron and zinc, vit C to aid absorption.
When MiL retired she sat a great deal, knitting, watching tv, drinking tea with biscuits, so after a couple of years she developed a pyramid shape, ballast, hence the difficulty rising from the sofa, then the stiffness moving.
My Gran always used a pouffe (remember those) to rest ner legs so ner feet would not swell and never had difficulty standing up
Also, you could try daily Magnesium, good for leg cramps, musculature, speak to someone knowledgeable in your local Health Store, if you are concerned as @Fraaahnces pointed out, a gp would lecture you about your weight without delving into cause and effect.