Disagree., low-fat and diet products are just a symptom not the cause. The cause is always eating unhealthy snacks between meals, particularly in the evening, usually crisps and chocolate. Show me a fat person and I guarantee they sit on the sofa in the evenings eating crap. Taking in calories when your body doesn't need it just before sleep means it goes straight on as fat. 

 "The cause is eating unhealthy between meals"

Yes but WHY do people get trapped by these constant cravings for snacks 24/7 in the first place?

Answer: Their satiation signals are out of whack, because they're deficient in protein and fat.