Maximize Your Success with the 40-30-30 Diet. Keeping a food log has been proven to be one of the most effective tools for people to make their diet get the weight off and keep it off. There are many studies that have shown that people who keep food journals are more likely to be successful in losing weight and keeping it off. In a six month study published in the American Journal of Preventive Medicine, people keeping a food diary six days a week...