For me, weight was an issue right from birth. Fast foods and ready meals werent really available in the 1960’s and 70’s and those that were around were despised by my mum. The foods we ate were healthy home prepared and, because of the weight issues, strictly limited - the medics had no answers despite testing thyroid function and checking for diabetes
Substantial weight loss only came when testing revealed a number of food intolerances and the elimination of those foods - v rapid weight loss (61/2 stone in 6 months) and an overall 10 stone reduction. Some things I came out as intolerant to would fit into high carb end ( white flour, banana, corn) others wouldnt ( dairy, eggs, tomatoes). The weight loss period was accompanied by an overall increase in calories, and , probably carbs - you try doing low carb or low cal on a diet of ,initially exclusively then v much centered on, lamb, lamb fat, brown rice and pears!
The weight loss was 15 -16 years prior to my diabetes diagnosis and was accompnied by several years on medications for food allergies (Nalcrom)