The British digestive tract has presumably developed in such a way that it can process the traditional British diet of red meat and green vegetables.
Accordingly, it might not digest curry sauce, pasta or the fodder disguised as watered-down processed poultry as efficiently as the previous indigenous diet. The consumption of such materials (I hesitate to call them foodstuffs) leaves the consumer unsatisfied; perhaps unsurprising, given that their body is looking for something else. Accordingly, those who eat them need to eat more than those who do not.
It's not dissimilar to the act of putting unleaded petrol into a diesel engine. The wrong fuel gets you nowhere.
Even with the providence of the supermarKKKets, a constant basic diet of red meat and green vegetables is well beyond the purse of a low-income, two-wage British household like mine; and there are only two of us here, no nippers to feed as well. Many of those who decry obesity are well-paid at our expense. It would be interesting to see just what foodstuffs they put into themselves and their families. I would bet that even when they think they are cooking adventurously, they are using ingredients that their bodies are programmed to handle.
The chicken nugget is capitalism's injunction to the people to 'Eat Shit And Die' - quite literally. It is not a foodstuff. It is a weapon of class war.