Let this never be asked about again.
***
In the last year or two, the above idea, taking a fairly extended period to return from dieting to maintenance has been called "reverse dieting" at least in the physique community. Basically in the same way that calories are often decreased over time while dieting, the idea is to gradually increase them when the diet is over. And while this is conceptually reasonable for the reasons I outlined above, some of the recommended durations are absurd and pointless to me.
Stories of dieters adding 5-10 grams of carbohydrate per week (which is actually almost unmeasurable in the first place) and spending weeks and weeks in a continued caloric deficit are common and taking weeks or months to raise calories is often recommended. Since this approach is often recommended to deal with the metabolic adaptations that occur with dieting, I fail to see how maintaining a low-calorie intake for 6 weeks to 3 months longer somehow solves the problem. And I see this as both pointless and ultimately self-destructive. Invariably, the idea is held up either as a way to slowly rebuild metabolism, which it doesn't do since all of the adaptation to dieting will more or less stay in place so long as calories are still below maintenance, or to avoid big water weight spikes. Certainly this second factor is a real issue, but I have to really question why the types of folks this approach is aimed at, typically post-contest physique athletes, can't get their head around the differences in bodyweight changes (from water and food in the GI) tract and actual body composition changes. Then again, telling a neurotically obsessed physique athletes not to be neurotic is like telling a cat not to cat. Regardless, from a physiological point of view, so long as you understand that any rapid weight gains are simply water and food in the GI tract, and that the water will be lost once the body get back into water balance, I see no point in taking more than two weeks to get from the dieting caloric intake to maintenance levels. Calories, both from carbohydrates and fats can be raised gradually day to do until the newly established maintenance level is reached. The same would go for the non-extreme dieter, adding food gradually over a two week period, maintaining the original dietary approach but with additions (in the form of pieces of fruit or even controlled amounts of carbohydrates and fats) gives the optimal balance between avoiding food problems and starting to reverse the metabolic adaptations that occur during dieting. For those who want more specific values, let's assume that the dieter is going to add 400-500 calories over this two week span. Divided daily that works out to 28-35 calories per day but since that's an amount of food that really isn't measurable, a plan of adding 100 calories every three days (this is about one piece of fruit or one cooked cup of rice or pasta) would fit into this scheme.
Related to the idea of reverse dieting is that of "building metabolic capacity". The idea here is that by gradually raising calories at the end of the diet, metabolic rate will increase and allow people to eat more without getting fat. Invariably the self-reports of people using this strategy report that they are "maintaining their bodyfat on much higher calories" but when you look at the actual numbers they are reporting, they are still in a dietary deficit relative to even their predicted adjusted maintenance. Basically, despite "eating more" these folks are still dieting and still prolonging the return of any sort of hormonal normalcy which, once again, will only occur once some bodyfat has been regained and they are at a near maintenance calorie level. Adding calories in a small amount in this way is simply delaying the process of any sort of metabolic or hormonal recovery towards even normal levels.
So why do these people maintain that they are maintaining their fat on "so many more calories"? First and foremost, while they may be eating more calories relative to the extremely low diet levels, they are still in in a deficit at the end of the day. The simple fact is that RMR only adjusts itself slightly (by perhaps 10%) over normal to increasing calories and only then when the body is being overfed above normal maintenance. And it takes fairly large scale overfeeding to even make that occur. RMR relative to bodyweight simply doesn't adapt that significantly in the first place (and any gain will be lost immediately when the next diet starts). Frequently they are also gaining weight fat/slightly and that alone is part of the supposed "building metabolic capacity" that is being reported.
This is compounded by the fact that the increased food intake is allowing these individuals to train more and harder. There is also the potential increase in NEAT since they aren't so exhausted from being on low-calories. They aren't gaining bodyfat not due to some magic building of metabolic capacity but because the energy out side of the equation is increasing as they are able to train more effectively.
The above terms, reverse dieting and building metabolic capacity are also used to describe a situation where, after reaching maintenance, individuals gradually increase calories over maintenance (once again at some drastically slow rate); effectively, in the same way that physique athletes often gradually decrease calories on the way down, they do the same on the way up. In premise this is supposed to raise the metabolic rate relative to current bodyweight with reports, once again, being of people "maintaining their bodyfat at much higher caloric intakes than before dieting." in hopes that during the next fat loss diet, calories won't have to go so low. But once again, research doesn't really support the idea. BMR only adjusts itself minimally with overfeeding and the impact on TEF is also minor. But when this slight increase is coupled with an increased amount of training and/or increases in NEAT, that alone can explain the supposed "new higher maintenance level". As well, when you consider how slowly true fat gain tends to be (even a 200 cal/day surplus is only predicted to increase bodyfat by maybe one pound every 3 weeks), it's easy to see how people can convince themselves that this is happening. There is often a slight weight gain during this time and that alone will serve to increase metabolic rate and the calories expended during activity.
All of which adds up to an increase in the energy out side of the equation but most of it is from factors that will disappear fairly quickly once the next dieting phase starts. Certainly starting with more muscle mass will have an effect but any increase in BMR relative to weight will go away, any effect from TEF will go away as soon as calories are restricted. It's currently unknown how quickly NEAT moves up or down but eventually it too will decrease as the body senses the energy deficit. So any of the so-called "metabolic capacity" which has been built will also disappear.
