Many diets restrict dieters to vegetables, coupled with at least 30 minutes of daily exercise, Some claim that this will, not only reduce stress levels, but will also generate weight loss. One study showed that, after five years, participants lost an average of 24 pounds on similar diet plans. The major drawback of a popular diet plan is that the diet must be prepared to consume only beans, fruits and vegetables and very little dairy, while avoiding all meats, oils and sugars. Many dieters will have extreme difficulty consuming a diet based wholly on vegetables, as this restriction can cause undesirable side effects.