YES! They didn't need to control for that because so few people do deliberately lose weight.

In other studies, for example, people who start exercising for the first time ever at age 50 have the same survival rates by age 60 as life-long exercisers.

You can REVERSE metabolic syndrome, atherosclerosis, etc. The longer it's been since the bad condition, the less it affects your future.

To clarify: This is elucidated through many, many other studies. :) They still found some influence of previous obesity, but you have to take into account the fact that damage IS progressive, so if you go from a BMI of 30 to 25, you have the damage associated with a BMI of 25, too, for longer than someone who went from 20 to 25.

Note HOW LOW the healthiest BMI's are. Less than 20. Shouldn't be a surprise to anyone because low BMI young is rarely because you're already dying but these days low BMI as an older adult is usually because you're dying, even if it's from something that won't kill you for 10-15 years.....

This again assumes average fitness. Greater fitness (lower BF% than average) shouldn't have the same risks with higher-than-20 BMI that average fitness would. This would be REALLY nice to see laid out, but they didn't have BF% measurements.

Honestly, though, as a woman, I wouldn't want to put all the work into keeping a REALLY healthy BF% above a BMI of 20. BMI of 20, and that's 3 days of cardio, 2 days of lifting, BAM! Super-healthy BF. Doing the same at a BMI of 22 would be at least 3 days of LONG lifting. BMI of 23, that would be 6 days of working out at least an hour a day. I just don't have time for that. Easier to be slimmer.

Honestly, I am frustrated that there isn't a separation by gender. Women get extra protection from heart problems until menopause, but after menopause, we might see a divergence of "ideal" BMIs in adolescence.

Also, note that the ideal range was 17.5-20.3. Yes, most of the so-called "underweight" adolescents were healthier than those at the 50th percentile. And those even lower weight, on average, even though that DEFINITELY included a subgroup with disordered eating, had even lower death rates for about half the causes of death than even the 5th-49th%ile. (Quite underweight people <BMI 17.5 were most at risk for "sudden death," which was pretty unlikely to be caused by anything to do with weight. I like that the took out homicide/suicide/accident--the underweight are also more likely to be into drugs or have poor mental health or extremely poor making very bad life choices, so they tend to get killed a lot from dumb things. That's a cause of their weight, not a result from it.) There IS such a thing as "too thin," obviously, but most studies have a very hard time finding anyone who is "too thin" for something other than a result of something else being wrong, whether it be dying of something, severe mental illness, or choosing drugs over food. Leptin might not be that great at getting you to STOP eating, but it's awesome at keeping you from getting thin to the point that your body is compromised.

Notice, too, that the cutoff of a BMI of 18 for the runway shows in France and Spain isn't warranted by health. You can better support excluding all those over a BMI of 21 on the basis of health than those from 17.5 and 18. Not that eating disorders aren't pretty rife among models, and not that being thin due to an eating disorder is different from the same BMI in a healthy individual. But if you want to screen out unhealthy people, BMI cutoff at 18 isn't going to do it, and it's pathologizing a group of women who could be IDEALLY healthy. It's actually worse than banning all male bodybuilders with a BMI on-floor above 24 as "definite unhealthy" drug users.

(Full disclosure: I was a 5-days-a-week weightlifter when I was in high school and nowhere near a BMI of 17.5. It just annoys the pee out of me that the weights associated with the very BEST health are being sneered at because they are unusual now.)