Here's some interesting research on weight loss from social psychologist, Stanley Schachter .

One question he asked was "How do taste and flavour affect the amount that people eat?

The following is Andrew Austin's interpretation on the work that Schachter did. 

In one of his experiments he invited 100 overweight people to a party and 100 slim people to another. He served milkshakes for refreshments. At the end of the parties, they measured how much milkshake had been consumed. As was expected, the overweight group consumed far more than the skinny group.

He then threw two more parties for the same groups, but this time he added quinine to the milkshakes. He added just a timey bit to ever so slightly taint the taste. What happened to the consumption was rather surprising. In the overweight group the consumption absolutely plummeted, while in the skinny group, the level of consumption only came down a little bit.

The inference from this study was that people with weight issues are naturally driven by flavour and taste. Flavour and taste are very important to them.

Another bit of research was called the Effort Hypothesis. Once again he threw two parties for 100 overweight people and 100 skinny people. Now he serves both groups peanuts. Again the overweight people consumed far more peanuts than the skinny group. However, when the parties were repeated and peanuts were again served, they were served in their shells. In other words one had to break them open in order to get to the nuts. There was a massive reduction in consumption by the overweight group, while in the skinny group there was almost no change at all. So this led to the Effort Hypothesis.

Now in terms of food preparation, overweight people tend to prefer food that is readily available. The slimming industry has clearly understood this and makes a fortune of money by preparing flavourful ready to eat meals which are easily and quickly prepared as well as very flavourful. 

Normal weighted people don't live on those foods. Only over weight people buy those foods. The advertisers gear their sales pitch to them. It's so popular to offer a shake or a pre-packed meal as this feeds right into the overweight psyche.