Welcome, newbie Jess!
As I have a great experience with Duromine I can tell your sister was right in a way.
First of all all people are different (metabolism, weight, height, etc.)
Secondly, for good weight loss you need: 1. diet (NO: low calorie, healthy, fried, fast food, ice cream, candies, mayo, ketchup, alcohol, smoking; YES: fresh fruit and veggies, boiled, steamed, stew veggies, chicken, turkey, beef and any low-fat meat, but again - no frying! Nuts, dried fruit, yogurt and all dairy, honey to replace sugar sometimes, olive oil, fiber).
2. exercises (many people mistakenly think the more they go on the treadmill - the more weight they lose) NO, NO and NO! Treadmill just warms up your body, any coach tells you this. Instead of torturing your body with hours of cycling, walking or running(!!!), combine different exercises. Warm up for 10-15 min. max on treadmill, step or whatever you have in gym, after that - some strength exercises are good. Arms, Legs and spine mustn't be ignored. Your body loses calories during strength exercises even more than on the treadmill, trust me. Squats and push ups will tighten your buttocks and arms and burn calories. Some abs is good too. No need to force yourself and do 20 at a time. If you can't - do 10 but 3 times with some breaks. Maybe a trainer will advice some more, just ask, or if you decide to work out at home, google 'workouts for beginners'. Physical activity is a must in weight loss, especially when you have much to lose! Because how do you expect the kilos will go away? When people try to eat nothing, they gain even more weight after the therapy, because their body accumulates fat "just in case" people will starve again, and the body still needs all nutrients for living.
Plus, after workouts you feel so good and energy is full.
3. keep a regime. Wake up at one time, take the pill and then some time should pass before breakfast. Small portion meals - 3-5 times a day! Lots of water. Good sleep. If you have sleep problems because of the pills, then take a small walk before sleep, ventilate your bedroom, avoid watching TV and working at PC at least 30 minutes-1 hour before sleep. Melissa, mint or any other herbal tea mith teaspoon of honey - help to sleep well. Maybe restful and calm music as a background set on timer so you can fall asleep...
Lots of different methods actually, you have to choose what's best for you
This way your Duromine pills will do their best! Many people cheat and lose either little weight or nothing..
Still, prepare yourself you will lose much in the first month and after that your body may take 'timeout' - it's normal. Give it some days or weeks to get used to the pills and diet.
I recommend you to write notes, diary maybe. Taking photoes of yourself every week - also good idea.
Try it and you will see you can lose as much weight as you want, no matter what other people say!
I hope these recommendations were not annoying, but helpful for you!
Take care and good luck!
Kate