Now that we have discussed the myths and presumptions, it is time to turn to what the authors of the New England Journal of Medicine paper consider to be “facts”.
These are statements about obesity, which the authors consider facts because there is sufficient evidence to consider them empirically proven.
As one may expect, “conclusive” evidence can only come from experimental studies (ideally, consistent findings from several well-designed randomised controlled trials, which constitute the highest level of evidence). Thus, it should come as no surprise that most of the facts identified by the authors pertain to issues that lend themselves to examination in such trials.
Obesity Fact #1 is that,
“Although genetic factors play a large role, heritability is not destiny; calculations show that moderate environmental changes can promote as much weight loss as the most efficacious pharmaceutical agents available.”
This fact is based on several studies that have shown that it is indeed possible to “modulate” genetic risk by changes to the environment (i.e. diet and exercise).
This finding is neither new nor limited to obesity. After all, even severe monogenic inborn errors of metabolism (like phenylketonuria) respond to changes in the environment (like elimination of phenylalanine in the diet).
However, it is important to remember that achieving lower weights for someone with a strong genetic disposition for obesity will always be so much harder than for someone without that genetic risk.
Thus, while environmental changes, which affect everyone, can perhaps reduce the average weight in a population, they will still leave the biggest people the biggest (albeit at a lower weight).
Just how big and feasible such environmental changes would need to be to significantly reduce obesity will remain to be seen.
At the individual level we have a fair idea that, for some people, this effort is likely to be substantial (readers may recall the recent series on Mark, Julie, Gertrude and Janice).
At an individual level there is certainly no doubt that some people are going to have to work much harder at trying to lose weight or keeping it off than others – so much at least, will always be destiny.