The Weight of Evidence 

Fat is fine. Not so! Weight control is important to health throughout our lives.

By: Dr. David L. Katz*

Scientific progress and the 24-hour news cycle go together about as well as a roof-top swimming pool and a lightening storm. The one is all about sending sparks flying, and the other is much better off in a state of calm. When it comes to a medical topic as perennially fascinating as weight control and its implications for health, the sparks start to fly.

Last week one of the top medical news items – based on a study in the prestigious Journal of the American Medical Association – was that in elderly people being fit matters, but weight control is less important. Naturally, the headlines trumpeted: “It’s Fine To Be Fat!”

The truth? The medical study did not, in fact, show that it’s fine to be fat – but subtleties don’t make headlines. The study did suggest that in a population of older adults being fit reduces the risk of death, whereas being lean but not fit does not. In fact a little extra weight offered some protection against dying. This doesn’t translate directly to “being fat is good,” but it makes for an eye-catching headline.

To confound matters, within 24 hours following these misleading headlines, a new top medical story emerged in the even more prestigious New England Journal of Medicine. The study – based on an evaluation of nearly 300,000 Danish children -- showed that being overweight in childhood is a strong predictor of cardiovascular disease in adults. In fact, early onset obesity powerfully predicts early onset heart disease – and the risk of premature death.

Put these two stories together, and you’ve got a load of sheer nonsense: Your weight is unimportant to your health, except for how important it is. Or perhaps we can make sense out of being overweight is somehow good for us when we’re old, but bad for us when we’re young so be careful to time the onset of obesity just right!

Since headlines are more interesting when controversial, they tend to maximize the discrepancy between messages, which only amplifies the mind-numbing nonsense.
My hope is that you won’t put up with medical news that makes no sense. I hope you are immunized against media medical follies by a bracing dose of common sense.
It’s important to keep level-headed when reading journalistic gibberish that relates to your health: One day we’re told it’s fine to be fat, and the next day that even a little excess weight can prove fatal. And to further the confusion virtually nothing within one 24-hour news cycle referred back to the previous 24-hour news cycle to acknowledge the incompatibility of the two messages.
So what’s the underlying sense? In this particular case, there is some actual disagreement between the two studies, although for the most part, they address different topics. Older people who become sick lose weight, and also become less fit. So being fit, in older people, is associated with less risk of death than being thin, per se. You can be thin because you are fit, but you can also be thin because you are ill.

But throughout life, being fit and being relatively lean are both important, and tend to go together. Data from the Nurses Health Study at Harvard have shown convincingly that being fat, and being unfit, make important, independent contributions to the risk of disease and death throughout one’s lifetime. Being fat actually exerts a slightly stronger influence. So headlines saying it’s good to be fat are misleading to the point of being dangerous. The facts:
Weight control is important to health throughout our lives.
Weight control in childhood is clearly of vital importance to the health of the adults our children will become. The threat of heart disease at an appallingly young age looms for children who become obese, or even, it seems, overweight to a lesser degree. We must all take arms against this, and the best way is for families to pursue healthful eating, and healthful physical activity, together.
In general, this is a lesson in how carefully we must interpret medical news. Science is not a ping pong ball: The fundamentals of healthful living do not change from one news cycle to the next.
But the headlines may suggest they do. Just because a study fails to find that a specific fruit fails to prevent a specific cancer doesn’t mean every good thing we’ve ever heard about eating fruit is no longer true! Headlines may well imply that, however.
Whether the topic is weight, hormone replacement, or new drugs for diabetes, what matters is not one provocative study, or controversial headline. What matters is the gradually accumulated weight of evidence.
As for the weight of evidence about weight?
First, fitness and many other factors influence health, too. And as one very important aspect of health, weight matters.
No matter what the headlines say, that will still be true tomorrow.

* David L. Katz, MD, MPH, FACPM, FACP; Director, Prevention Research Center, Yale University School of Medicine and medical contributor for ABC News. He may be reached at www.davidkatzmd.com.