Willpower and believing that one can succeed is important when dieting, but the perceived complexity of a diet plan might be the deciding factor when it comes to adherence. A small German study found that people were more likely to give up when they perceived their diet plan as complex – even when they rated high in willpower. The researchers suggest that if a diet has too many rules, people will find it harder to stay on that diet, and therefore that diet plan would probably not be the best choice for weight loss.