This has been intentional as in the past, the change in diet that has the most impact on me being able to lose weight "seems" to be dropping the so called "bad carbs".
It's total calories. 1 cup of cooked pasta is about 220kcal, to get 220kcal of broccoli would be 1.5lbs of the stuff. It's a lot easier to eat a cup of pasta than a pound and a half of broccoli.
So by reducing the energy-dense foods like jam doughnuts, pasta and so on, you tend to consume less calories over all. What happens when your income drops a little below your spending? You draw on your savings. For the body, that's body fat.
There's nothing "bad" about any food. It's just that some foods are calorie-rich and nutrient poor (like McDs) and others are calorie-poor and nutrient rich (like most fruit and vegies). When people come to my gym, I am usually less concerned with their calories than their nutrition - because they eat so much energy-rich but nutrient-poor food, they're overweight or obese but always tired and often sick, and have either diaorrhea (high fat diets from KFC etc) or constipation (high-starch diets from white bread etc) every day. If we can get them eating more fruit and vegies, well they might still be getting more energy than they need, but at least they're getting lots of nutrients and fibre - so they start feeling better, more energetic, not sick so often, and their digestive system offends them less.
Most financial approaches work - not just MMM - because it's the first time in their lives they're actually conscious of their spending. Likewise, most diets work because it's the first time in the person's life they're actually conscious of what they eat.