There are several ways by which you can do this, that too in the short duration of just a week!
But before coming to the methods, it is important for you to understand the concept of weight loss. It usually occurs when the body is expending more energy in work and metabolism than it is absorbing from food or other nutrients. It will then use stored reserves from fat or muscle, gradually leading to weight loss. Hence to lose weight one must burn more calories than they consume.
This could be achieved by either
-Reducing calorie intake and/or
-Increasing physical activity in the form of exercise.
A reduction in calorie intake can be achieved by consuming low-calorie diets. Due to their minimal detrimental effects, these types of diets are most commonly recommended by nutritionists ,they say that 55% of the diet should come from carbohydrates, 15% from protein, and 30% from fats with no more than 10% of total fat coming from saturated forms. ( Butter, ghee etc)
Most of us require an average calorie intake of about 2000 to 2400 calories depending upon our age,sex, type of work etc. It is usually not safe to drastically reduce this in a short duration of time, a reduction of 500 kcals per day is considered safe.This means that for a week as mentioned in your question, it is safe to reduce 3500 kcals.
Exercising enhances weight loss and improves fitness which could reduce your risk of several non communicable diseases too. Cardiovascular exercise helps burn calories whereas strength training can have weight-loss benefits by increasing your muscle mass,this will help you increase increase your calorie-burning metabolism. This means that by replacing fat with muscle, your body will burn more calories at rest.
Hence to lose weight, you will have to combine eating right along with increasing physical activity.Studies have proven that just exercise is responsible for 30% while diet control is responsible for 70% of weight loss. You could reduce your calorie intake as well as exercise with a lot of vigour but it is considered safe to lose just 1 or 2 pounds a week.
Some other tips that you could utilise to lose weight are
-Eat a high-protein breakfast.
-Avoid sugary drinks and fruit juice.
-Drink water a half hour before meals.
-Choose weight loss-friendly foods
-Eat soluble fiber.
-Drink coffee or tea.
-Eat mostly whole, unprocessed foods.
-Eat your food slowly.
Also it is very important for you to keep in mind that basic body functions like breathing and making cells etc use about 50-70% of one's calories.The resting energy expenditure of one's body depends on their basal metabolic rate and this could vary from person to person based on their genetic make up, hence some people might have to work harder than others to lose weight.