This is fundamentally true but I usually add this caveat: All calories aren't equal.
Having a negative energy balance is going to ultimately lead to weight loss, yes. But it's important to eat good foods (whole grains, fruits, vegetables) so you 'feel better' even though you're eating less calories.
This journal article (A Role for Sweet Taste: Calorie Predictive Relations in Energy Regulation
by Rats: http://www.apa.org/journals/releases/bne-feb08-swithers.pdf ) is about a comparing natural and artificial sweeteners. The point of the article is the rats fed artificial sweeteners gained more weight than the rats fed real sugar.
It's just a little evidence in support of the original author's assertion that 'Light products are for pussies.' The truth is that while that Diet Coke may have less calories in it, it can also lead to an increase in appetite (read: weight gain.)