I get a few people that come up to me after class and ask how quickly they can acquire a six pack. I ask about their routine AND their nutritional/dietary plan to see how things can progress. Much to their dismay, I tell them it takes TIME to burn fat and build lean muscle. The body unfortunately does not accumulate muscle in one area, and fat in the next. We can't direct our organs and tissues in that way..
In this culture, we're primed to want the easy fix. 'Take this pill and you'll lose x.' 'Take this supplement and you'll gain y.' The issue with this method of thinking is that it convinces people that the best results come in a short amount of time. Sometimes we have issues with the idea that the short-term won't bring about drastic change. I read the other day "For every diet, there is an equal and opposite binge." I couldn't agree more. Despite the time and effort, many diet goers end up in a perpetual cycle of gaining and losing weight. I can't speak for all diets, but the ones that promote heavy restriction and extremely low calorie intake are both unrealistic and unable to be maintained. If someone did need to follow a low calorie restrictive diet for the sake of their health, that is best handled with the supervision of a registered dietitian.
Ultimately, our bodies aren't meant to lose 5-10 pounds in a week. At the end of the day, our body is an accountant. Energy balance is vital when it comes to losing weight, so by calculation (maybe investing in a food journal) it's possible and sustainable to lose weight steadily over time through healthy means. A pound measures out to be 3500 calories, so exercising on a consistent basis coupled with careful and cognizant nutrition will lead to more success than any 'quick fix.'
