people who do lose weight effectively, Al Roker Weight Loss the most viable target is a loss of about 10 percent of their highest weight. That's the number recommended by the National Institutes of Health for people who are obese or overweight. Losing more than this can be difficult and is rarely effective. Many people attribute this lack of effectiveness to poor willpower on the part of the dieter, but recent research has shown that the problem is more complex than this. A 2011 study in the New England Journal of Medicine showed that losing weight changes the way the body produces hormones associated with metabolism. This means that people who attempt to reduce are hungrier and suffer from higher appetite levels than they did before the loss. This lasts for at least one year after weight loss, making it far more difficult for someone who has dieted to maintain a lower weight than it is for someone who has never undergone a weight loss program.