You've resolved to do all the right things to stay fit and healthy in 2013 – but that can be challenging when scientists keep changing their minds about what "right" is. Here are six topics to keep an eye on in the coming year, where scientists will be presenting new evidence that will help keep us on the right track.
The obesity paradox:
Until recently, few people questioned whether being overweight is bad for you. But lately, critics have argued that carrying a few "extra" pounds carries no health penalty, and in fact might help you live longer.
WHAT WE KNOW The relationship between weight and mortality follows a U-shaped curve: Those at the extreme low and high ends are at the highest risk. But it's not clear where the lowest point on the curve is, or how steeply it rises.
WHAT WE'LL LEARN IN 2013 Sorting out the confounding role of factors like smoking and serious illness – which first make you lose weight and later make you die – is a top priority for epidemiologists. More generally, the chicken-and-egg debate about whether fitness or fatness is a better predictor of health will continue.
Running in wispy "minimalist" shoes – or no shoes at all – has made a rapid passage from fringe curiosity to mainstream activity. Now research studies that were launched in 2009 and 2010, when the movement took off, are finally producing results.
WHAT WE KNOW When you take your shoes off, you change the way you run, taking shorter strides and absorbing more force with your ankles instead of knees.
WHAT WE'LL LEARN IN 2013 The burning question is whether these changes reduce your risk of injury. There are reasons to think this should be true, but proper randomized studies take time – which is why we'll finally start accumulating meaningful data this year.
Pollution and exercise:
Every summer, city-dwellers have to choose whether – and where – to exercise when air quality takes a nosedive.
WHAT WE KNOW Inhaling particulates emitted by cars and trucks spurs inflammation that spreads throughout the body. Exercise, on the other hand, helps your body fight inflammation. But which effect wins?
WHAT WE'LL LEARN IN 2013 Don't expect a black-and-white final answer: Any urban exercise inevitably involves trade-offs that will vary on an individual basis. But expect more guidance from forthcoming studies on how much you can exercise, and at what pollution levels, before the negatives outweigh the positives.
Supplements vs. foods:
One ironclad certainty is that you will read a bewildering stream of news, often contradictory, about supplements that may or may not change your life in untold ways.
WHAT WE KNOW Foods contain literally thousands of chemicals and components that combine to keep us alive and healthy. So far, extracting a single element from healthy foods and putting it in a pill has failed to match the benefits of those foods.
WHAT WE'LL LEARN IN 2013 Researchers are beginning to focus on the broader context of dietary patterns, stepping back to understand healthy eating as a whole that's greater than the sum of its micronutrient parts.
Overdosing on recovery:
Top athletes have access to an endless array of sophisticated recovery aids, from "cryosaunas" to compression machines. But experts are now wondering whether it might be too much of a good thing.
WHAT WE KNOW Post-workout aids like ice baths and anti-inflammatories can help limit muscle damage and accelerate repair after intense workouts. But in doing so, they may suppress the signals that tell an athlete's body to adapt and get stronger.
WHAT WE'LL LEARN IN 2013 It's a simple question of whether the benefits of quicker recovery outweigh the downside of reduced adaptation. The only way to find out is to run experiments, which is what researchers are doing now.
The old debate about nature versus nurture as the driver of health and athletic success has a new twist. While you can't change your DNA, you can change which bits of your DNA are active or inactive through what are known as "epigenetic" adaptations.
WHAT WE KNOW A single hard workout can switch on previously dormant areas of DNA that affect how you metabolize energy. Other studies suggest that epigenetic changes allow environmentally driven traits such as obesity to be passed from parent to child.
WHAT WE'LL LEARN IN 2013 This is a young field, so there's plenty to learn. How do we turn these epigenetic switches on and off? How long do changes last?
Alex Hutchinson blogs about exercise research at sweatscience.runnersworld.com. His latest book is Which Comes First, Cardio or Weights?