I was recently asked (again) by a journalist about the research into the power of exercise when it comes to weight loss, so I dug through my research files for the single best research article I could find. These experiments can often be more meaningful than meta-studies that are contaminated by poorly designed studies.
As my regular readers know, exercise and weight loss do not have the expected relationship. Don’t get me wrong exercise is important when it comes to cardiovascular fitness and for managing stress, depression and anxiety. Indeed these emotional benefits, for me as psychiatrist, are its real power. But when people exercise to lose weight they often do not realise how little benefit they are getting for so, so, sooo much work!
From a psychological perspective the issue is that people exercising to lose weight drain their precious motivation – which often comes in spectacularly limited amounts in the first place. In the research this is referred to as ‘motivational fatigue’. But there’s a much bigger problem here that few professional appear to fully appreciate.
There are not many well-designed studies that look at the effect of exercise alone in the absence of dietary change, when it comes to losing weight. Why is this study, The Midwest Exercise Trial by Joseph Donnelly et al*, the best study I have seen? First, they actually supervised the exercise in the gym so we know it happened and how it happened. Often when I present this kind of evidence Personal Trainer-types argue, “But they obviously didn’t keep it up,” or “They were doing it wrong”. No, this is as good as exercise gets.
Second, it runs over a long term i.e. 16 months – an impressive timeframe given that most studies are only funded for 6 months or less. Third, it was goodly amount of exercise at 5 days a week, 45minutes duration and intense enough (mostly treadmill workouts) to burn at least 400Cals per session. This is more than most people can achieve when they head to the gym. Fourth, 74 people completed the study which is a large study group for this kind of research. Of course, it was randomised with a control group.
So what happened? Well for women, pretty much nothing when it comes to weight loss! After 16 months of hard work, “Women in the exercise group maintained baseline weight, body mass index, and fat mass.” This is an optimistic way of saying they not only lost no weight at all, but no fat either!! This is the bigger surprise for most. As I explain in Weight Loss for Food Lovers there are a number of reasons for this, but the main one is that people are hungrier and feel justified in eating afterwards. It is just so easy to eat an extra 400Cals and not even realise it.
Men lost an average of 5kg which is more than most studies, but this still works out to losing around just over 0.3kg per month. We can easily achieve a 5-fold better response with a good energy intake plan (that of course does not create any emotional deprivation). There are other studies that show similar results, but if I had to pick just one, this would be it.
One thing that eating less cannot do
Once you understand the psychology, you realise that people need to tackle the exercise challenge before or after they plan to lose weight, not at the same time. It is just too much to ask of most people – do not risk the motivational fatigue that saps that precious commodity – motivation. I advise my patients to lose weight primarily through developing a healthy eating lifestyle, then move onto exercise once this is in place.
Then there is one thing that exercise has over weight loss through lowering your energy intake – exercise can shape specific parts of your body. Beyond the benefits I mentioned above, this is where exercise comes into its own!
If you would like help with Motivation then click here to find out about my latest online programs into motivation and the foundation it is built on – Mindset.*Full reference: Effects of a 16-Month Randomized Controlled Exercise Trial on Body Weight and Composition in Young, Overweight Men and Women. JE Donnelly et al, Arch Intern Med. 2003;163:1343-1350.