Exercise is very important to overall health.  As mentioned in an IFOD a few days ago, strength (as measured by grip strength) is inversely related to all sorts of bad health results. While exercise will increase your fitness and overall health, one thing it doesn’t do well  is help you lose weight.

Maybe you’ve experienced this paradox.  You adopt a disciplined and vigorous exercise program and yet the weight just doesn’t come off.  I’ve run four marathons, and averaged over 50 miles a week of running during the months of training, and all those extra calories burned running resulted in zero pounds lost! 

Studies over the past ten years have confirmed this paradox.  A recent study of the Hadza – a hunter-gatherer tribe in Africa – found that the Hadza men ate and burned about 2,600 calories a day and the women about 1,900 calories.  That is the same as the average adult in the U.S. and the Hadza are much more active than the average American.

Another study of obese women placed on extreme calorie restricted diets found that the groups that exercised in addition to following the calorie restricted diets did not lose any more weight that the group who just followed calorie restriction.  Many other studies have found similar results.

How does this happen?  Experts are not sure.  Basically, our bodies have evolved to keep our energy expenditure in check.  It is possible that highly active people change their behaviors to conserve their energy in other ways when they are not active.  Or, that our bodies reduce the calories spent on unseen tasks within our bodies such as inflammatory immune response. We aren’t sure. Our bodies evolved to keep our weight pretty stable – we consume about one million calories a year, yet our weight remains pretty constant from year-to-year.

So, we’re left with the following conclusions based on available information:

1. exercise, especially strength and resistance training, is VERY important for overall health, but
2. it’s your diet that is main driver of fat gain and loss, and
3. your body wants to keep you at your current weight.

So, the adages that “abs are made in the kitchen, not the gym” and “you cannot outrun a bad diet” are true. AGAIN: exercise is HUGELY IMPORTANT for all sorts of reasons, but if you are wanting to lose fat its your diet that will move the needle.

Primary source and more reading from Scientific American: Scientific American

Here’s a great article from VOX on this topic: Why you shouldn’t exercise to lose weight, explained with 60+ studies

Another really informative article on this topic:

http://junkfoodscience.blogspot.com/2008/10/first-law-of-thermodynamics-in-real.html