If you can't resist eating an entire bar of chocolate in one go, the solution could be simple.
Unwrap it and break it into all of its individual chunks before tucking in.
Research shows that people eat less when presented with several small pieces of food rather than one large one - even when the two contain the same number of calories.
It isn't entirely clear why this is so, but scientists believe it could be down to an optical illusion, with the brain and belly fooled into thinking that a bar of chocolate broken into pieces is bigger than one that remains whole.
Similarly, a muffin may suddenly seem more filling if cut into quarters before taking a bite.