The fastest way to lose 100 pounds is to consume fewer calories than are burned each day for an extended period of time. One pound is roughly 3,500 calories, so a 500-calorie deficit each day typically results in roughly 1 pound lost per week.
For most people it is safe to lose up to 3 pounds per week, though individuals over 250 pounds may safely lose more than that per week. Loss of water weight due to reducing starches and sodium can result in up to 5 pounds lost in the beginning. On average, 100 pounds can be lost in roughly 10 months. Reducing caloric intake and adding exercise to one's daily regimen are the most effective ways of creating a deficit for weight loss.
Vegetables are filling and contain very few calories, so including large portions makes it easy to stay within a calorie budget without being hungry. An accurate, regular food journal keeps dieters accountable and provides a visual record of how many calories are consumed. This also makes it easier to measure how specific foods affect weight loss or gain.
Increasing daily activity allows a person to eat more calories while still retaining a deficit. A mixture of cardio and strength-training exercises provides a balanced exercise regimen that burns extra calories.