What personality trait best predicts who will be overweight?

Impulsivity:

People with personality traits of high neuroticism and low conscientiousness are likely to go through cycles of gaining and losing weight throughout their lives, according to an examination of 50 years of data in a study published by the American Psychological Association.

Impulsivity was the strongest predictor of who would be overweight, the researchers found. Study participants who scored in the top 10 percent on impulsivity weighed an average of 22 lbs. more than those in the bottom 10 percent, according to the study.

Source: Science Daily