Indeed, temptation exists, immoral marketing campaigns with large sums of money behind them exist and children are more susceptible to these things. I still hold people responsible for their own actions though. I just don't find it acceptable that people can claim that they're not in control of what they eat. It's not always easy, but then that's life.
But this is the problem isn't it, it feels like there's a cognitive dissonance occurring;
If you accept that large sums of money are being spent deliberately to target children in selling unnecessarily high-energy, hyper-palatable junk food that only harms them (which you agree with). Which ultimately leads them to engage in behaviors which they carry on into later life, resulting in them being obese into adulthood, (which you agree with) then it's simply illogical to say 'they're responsible for making those choices, so it's ultimately their fault'
It's illogical, because left to their own devices, in a world where they're not targeted and bombarded by the food industry, they wouldn't become obese and there wouldn't be this problem - because obesity didn't exist as a problem until the processed fast-food industry was created in the 1980s, it's the environment we've created which is the driving force behind the issue, not personal choice, surely you can see this?