>(One study found that a group of people who lost 10% of their weight through dieting had their resting metabolism decline by an average of 15%.)

Can you post a link to this study?

>We don't actually know how TDEE reacts to weight loss in general

I don't think this is something "we don't actually know." Lots of weight loss studies have been done in which energy expenditure has been carefully measured, so there's plenty of data on this.

Okay, this is a survey from 1998 - my google-fu was not strong enough to find one more recent:

http://fampra.oxfordjournals.org/content/16/2/196.full

Quote: "...the majority of the studies point to a reduction in short-term resting metabolic rates that is greater than can be explained by the loss of body mass or fat-free mass over the same time period. Unfortunately, there has been very little work done over the last few years regarding the duration of this phenomenon.

[...]

This is relevant for motivated patients who adhere to severe hypocaloric diets to achieve rather large weight losses. When they get to goal weight their metabolic rate is severely depressed, and they can experience almost immediate weight gain if they resume their prior higher calorie intakes. Recent studies have not continued to measure changes in resting metabolic rate for extended periods to determine whether the reductions are self-limiting. "

The term used these days is "adaptive thermogenesis". You can browbeat it anyhow by sufficiently undercutting caloric intake that the body can't down-regulate enough to cover the deficit. A much safer and easier way to do it is either to use a moderate deficit (studies of athletes show that with identical exercise and identical protein intake, athletes on a 500kcal deficit retain more strength and lean mass than athletes on a 1000kcal deficit) and do exercise, at least some of it with weights.

There's also the "rebound effect", which the Minnesota Starvation Experiment gives us insight into.

People stop dieting and then resume ad libitum eating. They gain fat faster than lean tissue, because gaining fat is easier than gaining lean tissue. Net effect: BF% worsens compared to baseline.

The key is not that "diets don't work, look, they make you fatter"; rather, it's that people see diets as something you do once and then stop. What's actually necessary is ongoing control of food intake.