People who are naturally slim only eat when they are hungry, but those
with weight problems tend to eat more when food is available so it is
necessary for them to be aware of this and react accordingly if they wish to avoid gaining weight.
Those who have difficulties in the presence of attractive food must avoid this situation completely, e.g. by buying flowers or telling people about it.
Where children are concerned it is unwise to accustom them to weekend
goodies if they are to avoid overweight as adults, or even long before
that. The emphasis should always be on essential nutrition, e.g. fruit. If you feel you must give them weekend goodies, just buy enough for them to consume at once.