It is possible to lose a lot of weight in a week, but if you do this, the weight you lose is usually water weight, which means you'll gain it back when your diet returns to normal. To lose one pound in a week, you have to cut 3,500 calories from your diet, or about 500 calories a day. Do this with a combination of diet and exercise, and base your diet on fruit, vegetables and small amounts of lean protein to keep your energy up.
Drink water. Water can make you feel more full between meals, and if you drink a couple of glasses before each meal, that feeling of fullness will help you eat less.
Eliminate carbohydrates such as bread, pasta and rice from your diet. These tend to cause bloating and weight gain, so cutting them from your diet temporarily is a good way to lose weight quickly.
Eat mostly fruit and vegetables. These foods are high in vitamins, minerals and fiber and low in fat. Filling yourself up on fruit and vegetables will help you drop weight quickly without sacrificing your health.
Replace a couple of meals with liquids. At breakfast, make a banana smoothie with milk, a banana and protein powder. For lunch or dinner, have a bowl or two of a broth-based soup with meat and vegetables. These will help keep you full without a lot of calories.
Include a small amount of lean protein with every meal. This could be a half-cup of beans in your soup at lunch, or a lean chicken breast the size of your palm at dinner. Adding the protein will help keep you full and fuel your muscles.
Exercise every day. Cardiovascular exercise is most effective at burning calories, which you want to do to lose a lot of weight. Exercise an hour each day, keeping your cardio as intense as possible. Include weight training in your exercise routine a few times a week to help build your muscles. By building your muscles, you will burn even more calories than if you just dieted.