First, I have some bad news: exercise is rather bad at creating weight loss in absence of dietary interventions. And if you want more proof, there’s this, and this, and this, and more if you care to look. However you should notice that all of those studies indicate positive metabolic outcomes in spite of the lack of fat loss. It’s something I tell my clients all the time: exercise is the great optimizer. It accelerates fat loss when your calories are in check, and it reduces the rate of gain when they’re not by improving the nutrient partitioning of those excess calories via hormonal mechanisms. Exercise can also do what drugs and diet cannot and this is the important part. First, more bad news: our genetics have long ago determined performance outcomes of any exercise we do. Really.
In the BBC documentary “The Truth About Exercise” we get to see how much our genetics determine improvements to our fitness:
I’m an exercise science grad student and can attest to how little calories are burned during exercise. If it burned as many calories as people would like it to then going to the grocery store would render us exhausted before we made it to the diary case. Beyond that, many of the reasons people train (e.g. performance and cosmetic reasons) are genetically determined with little wiggle room…well, steroids can overcome some of this but it only moves the ceiling up a few feet. To see more studies from one of the main researchers, Dr. Timmons, see this, and this, and this.
However, and this is important, notice that the health outcomes improve independent of performance improvements. A 23% increase in insulin sensitivity, and a 15% increase in the rate of glucose clearance is a huge amount; there are Type-II diabetics with a cabinet full of drugs who haven’t gotten numbers that good. And yet, because of the healthcare model in this country and the litigious nature of our society, doctors won’t prescribe meaningful exercise as a treatment even if they would like to do so. Australia, it seems, doesn’t have that problem.
In the land of the Tall Poppies, exercise is now being prescribed as treatment for a variety of things we already knew it helped (osteoporosis, diabetes, cardiovascular function) and for a variety of things we’re just now learning it helps (cancer). I cannot embed the video so you’ll have to view it here.
So there it is: if you want fat loss, clean up your diet; if you want to improve every aspect of your physical self from atom to organism, train briefly, safely, and intensely.