Hi! could you perhaps explain to me why diets are generally ineffective? it's for my research paper.

Many possibilities: While experts generally agree that diets only help temporarily, there is not necessarily a consensus about why this is. There are several theories. They don't give us enough space here but this fine essay explores various explanations: http://www.fatnutritionist.com/index.php/why-diets-dont-work/

Yes: Many diets do not teach the person about lifestyle changes and long lasting changes that they can incorporate into their everyday life. Many go on crash diets with radical changes that cant be sustained over time. A lifestyle change would be to eat more fruits and vegetables and less fried and fatty foods. That is an attainable goal that could result in a more permanent weight loss.

People don't follow: them. Food/diet is among the most automatically run things. The mesolimbic (emotional center), the hippocampus/thalamus selects which inputs are noticed (salience), amygdala (drive) run things. We IMPRINT on foods, cues/triggers run habits. These run without cortical input. http://www.amazon.com/dp/0692496157/ is how to actually deal with this, and has all the references.