Here is an essay arguing that genetic reductionism is false, and that genes do not really cause anything. It has many scientific references, mostly pointing to weaknesses in heritibility studies. For example, a study might assume that twins reared together would have shared the same environment, but there could have been slight differences.
What I get out of this is that heritibility research is very upsetting to some people. They would much rather believe that people are the result of proper rearing, nutrition, and schooling, as then there would be hope for social programs to improve and equalize opportunities. Those programs cannot do anything about genes.
I post this just to show what is behind the genetic denialists. Their arguments do not make any sense to me, but read them yourself.
Here is a NY Times essay in favor of fat acceptance:
But the guidelines are rooted in a premise that should have been rejected long ago: that weight loss is the best path to health and happiness. ... we face an epidemic of anti-fat bias, which results in the stigmatization of fat people in schools, workplaces, doctor’s offices and other public spaces. ...Yes, BMI is a crude measure and has its limits. But it is still a useful measure of obesity.
And yet by framing the new guidelines around the best ways to pursue and achieve weight loss for kids, the academy reinforces that bias. It relies heavily on B.M.I. as an indicator of health status, even though mounting evidence reveals its limits. B.M.I. may be less reliable when used in kids because it doesn’t consider a child’s muscle mass or level of pubertal development, both of which influence body composition.
Note that she is terrified of the new guidelines for all the wrong reasons. We should be terrified that pediatricians are so eager to recommend extreme medical treatments of fat kids.