Rules for Our Annual Biggest Loser Weight Loss Competition You must weigh in for first and last week and it is required to be done with our scale or with one other competition participant present to keep us all honest. The Winner will be determined by the highest percentage of weight lost and will take 80% of the fees collected second place will take 20%. There is the option to not weigh in for 2 of the 12 weeks but you must weigh in the first and last week to qualify for a winning position. The percentage of weight loss calculation: (pounds lost ÷ beginning weight) X 100 = percent weight lost