To lose 50 pounds in 4 months you will have to lose 3 pounds per week. This is something more than the recommended weight loss of 2 lbs per week. If you have an enormous body weight to lose and 50 pounds is just the initial amount of weight you have to shed then it might be possible. If not, it will take some more time to shed 50 pounds but you will still be able to lose a noticeable amount of weight in 4 months.
Slow and steady wins the race. Therefore aim to lose from 1 to 2 lbs per week which is safe and recommended weight loss. Programs like Nutrisystem and Medifast helps you lose weight at steady manner. Both programs claim to offer weight loss from 1 to 2 lbs per week if their dietary guidelines are strictly followed. Nutrisystem asks its dieters to follow Turbo 13 plan in the first month which helps them lose up to 13 lbs and 7 inches in the first month of following it. This is great to kick start your weight loss journey. Medifast is another well known program that delivers low calorie replacement meals to help you lose weight as quickly as possible. You can go through the comparison article on these diet programs at Jane-Seymour site.
If you consider a 53 year old woman of moderate height weighing about 180 pounds, she has to eat around 500 calories per day to lose 50 pounds. This is not recommended as she would be nearly starving without food which leads to nutrition deficiency. If you want to have a safe and sustainable weight loss it is recommended that you go slowly. Women should eat around 1200 calories per day and men should consume around 1500 calories. If you are not sure about the timeline within which you have to lose pounds you can consult your doctor.