Which of the following reasons explain this example: deakon knows that soda is not healthy for him and he continues to drink a can of coca-cola every knowing isn't equivalent to changing behavior.

The food adulterants and the chemical compound present in the food are harmful for the living organisms. The junk food increases the chances of obesity and health related disease.

The humans knows that the smoking and excess drinking of coca cola can cause harmful effect in their body. But this is human psychology that the knowing about the harmful effect of a particular substance cannot change the drinking or eating behavior of an individual.

a mother eats twice as much to support her growing fetus

limiting sugar intake in a mother with gestational diabetes, switching from diving to swimming.   depending on whether the patient is normal weight, over weight or gain will differ depending on that.