Answer to Question 1
Answer: Do not try to change your entire life at once because your self-control muscle will get tired quickly and you will be more likely to give up. For example, many people make a New Year's resolution to lose weight. They give up dessert and pizza and start going to the gym every day. But this is really hard to doin lab studies, people who exerted self-control on one task (say, eating radishes instead of cookies) were more likely to fail at another task that required self-control. To use the analogy of a muscle again, self-control can get tired if used too much during a short period.
Answer to Question 2
Answer: Impulsivity is linked to obesity. Highly impulsive people weigh 24 pounds more than those very low in impulsivity. This makes some sense: Few people have a sudden impulse to eat broccoli or chicken. But it is all too common to crave fattening food such as pizza, pastries, and desserts, and often difficult to limit yourself to two cookies instead of the whole box.