I disagree with some points here. The reason why people gain their weight back from losing it fast is because, when they get to that goal number on the scale or close to it, they stop their diet cold turkey, then a couple weeks later they’re in complete shock to discover that they gained weight.
Weight loss depends on how much weight a person wants to lose. If it’s 10 or 20 pounds, a slower weight loss is best, but if someone has significant weight to lose, they can lose weight fast without even trying nearly as hard as a person who needs to lose less.
By the end of my pregnancy I had gained 50 pounds! I’m short, so that is a high number for someone like me. When I got home from the hospital, I was excited to step on the scale and see that the number had gone down significantly. Do my disappointment, I had not lost any weight! It was depressing. But it got be motivated to go on a serious diet plan. I went on an Atkins type diet, and lost 45 pounds in 3 months. When I saw that the bulk of the weight was off, I SLOWLY started to add healthy carbs to my diet. I then created a well rounded healthy eating lifestyle plan. The plan included whole grains (including fiber), protein, fruits, vegetables, a multi vitamin (suggested by my Dr.) I also allowed myself ONE cheat meal a week as a reward, and something yummy to look forward to every week. I also added exercise, such as running, yoga, strength training. I lost the remainder of the weight I needed to lose a couple months after that. My baby is just about 2 years old, and I haven’t gained that weight back. I gain the occasional few pounds around holidays, and when aunt flow comes for a visit, but lose it pretty quick.
So losing weight fast is not a problem, you just have to monitor your health and make sure you aren’t depriving yourself of the proper amount of calories, and nutrients you need. You also have to be aware when it is time to stop the “fast weight loss” diet and slowly bring yourself up to a well balanced, healthy LIFESTYLE type of eating. Also, don’t forget to include exercise. You should be getting at least 30+ minutes of cardio most days of the week, and include strength exercises during the week.