I don't believe in the 'starvation mode' stuff...
Instead, there is average weight loss, not linear weight loss. Over x number of days, you lose y number of pounds. With ups and downs, it's just an average. The 'ups and downs' don't always look the same on a chart and if you are strictly measuring food and limiting calories, the end result is that you lose a certain number of pounds over a certain period of time.
You pick the time period. If you use 'two weeks,' you're going to be disappointed because the first two weeks of weight loss tend to reflect water weight loss along with everything else. It's not going to be sustainable. But, over the longer run, it definitely contributes to keeping your average weight loss looking good. If you look at the last two weeks of a diet, it would discourage you - but those last two weeks aren't the whole diet's success story, either. They contribute to the average but they don't stand alone.
It's averages, not daily success or failure. This is a blessing - and a curse!