Sarcopenia is the degenerative loss of skeletal muscle mass. This happens with age and it also happens with weight loss. In the study review "Human Biology of Weight Maintenance after Weight Loss" by Edwin C.M. Mariman I was struck by this.
"As the closely related basal metabolic rate is largely determined by fat-free mass [14, 15] , it can be assumed that a fat free mass sparing effect is strongly involved in the risk for weight regain  . In this respect, the ratio of fat mass/fat-free mass in the lost weight could be easily higher for people with a high baseline body fat content, giving them an advantage with respect to the risk for weight regain."
Here is the link to the study.
My suspicions that long term calorie restriction coupled with steady state cardio as a recipe for weight regain seems to be well founded. Both steady state cardio and VLCDs take weight off rather indiscriminately. I experienced this personally.
Cardio is not muscle sparing, strength training is. I've been fighting to put this muscle back for almost 2 years and have finally seen some success. Two things have worked for me.
1) Stop doing cardio.
2) Strength train.
I'll add some wrinkles to both bullet points. Cardio can be fun for some folks, but it's a chore for most. If you love it, keep doing it. It is likely to your detriment with regard to body composition and if you're struggling with maintenance, you're likely making it harder for yourself.
But what about my heart health?
There is sufficient stimulus of the cardiovascular system during intense strength training that a person of reasonable aerobic capacity can largely maintain or improve VO2max. Also, one HIIT session per week not to exceed 30 minutes will build aerobic capacity sufficiently.
Second item, strength training. Most people don't have a clue, myself included, until fairly recently. I have seen the most long term success (measured by progress in absolute terms we all understand, like pounds on a bar through full ROM) with barbell training with progressive overload. This is not P90X, bodypump, pink dumbbells or assorted videos. Most of what I'm doing can be found here.
See the section "Practical Programming (2nd Ed) Novice Program"
If you're not familiar with progressive overload, see:
These two items have done two very wonderful things for me. First, maintenance is a breeze. I've completely stopped tracking my intake and have ratcheted back my scale watching because it doesn't move much. Second, this workout can be completed in about 30 minutes. I do it once or twice a week. That's it.
Hoping this reaches some of my friends who might be struggling.
Also, we started a discussion about this on the Maintainers forum on SparkPeople.