For years, nutritionists have tried to come up with a diet that will guarantee weight loss without fail. Mass production of low-fat or no-fat food varieties has not helped reduce the obesity problem in the United States, and various diets have worked for some people and not for others. Now some scientists say there is no one-size-fits-all solution for weight loss and that only personalized diets work. VOA’s Zlatica Hoke has more.