There’s a quite widely-held view that the solution to obesity is simple – we just need to eat less and exercise more. Despite the sense that seems to surround this notion, the reality is that such strategies generally fail to deliver significant weight loss benefits in the long term. I have written before about the now voluminous evidence that shows that regular aerobic exercise (such as brisk walking) generally fails to shed pounds.
This is not to decry exercise, by the way. I actually believe that activity is one of the key components to physical and emotional wellbeing. Is it absolutely essential to be active to healthy? I don’t know, to be honest – but I’m convinced it helps.
However, I was reminded of the relative ineffectiveness of exercise for weight loss this week by the publication of a study in the print edition of the International Journal of Obesity [1]. I actually wrote about this study here when it was first published on-line back in September.
In this study, 320 post-menopausal women were randomised to one of two groups:
- an exercise group, instructed to engage in moderate-to-vigorous exercise for 45 minutes, 5 days a week.
- a control group, who were not to change their normal activity habits.
Both groups were asked not to change their diets. The study lasted a year.
At the end of the year, women in the exercise group were found to have exercised for an average of 178.5 minutes a week. This equates to 155 hours over the course of the year.
Compared to the control group, these women lost an average of 1.8 kg in weight. Loss of body fat was 2.0 kg (suggesting that the exercising women put on a little lean body mass compared to the control group). They also lost 2.3 cm (about an inch) off their waist circumferences.
Now, again, I believe there are benefits to exercise that go way beyond any loss of body fat. However, if we do the maths we see that women exercised for about 86 hours for each kg loss in weight.
Overall, dietary change appears to be significantly more effective for weight loss. And adding exercise to dietary change, appears not to add significantly to the weight loss benefit. Two major reviews have found that when exercise is taken alongside dietary change, the additional weight loss benefit is in the order of 1 kg (about 2 lbs) [2,3]. In other words, if someone loses 10 kg by changing their diet, adding regular exercise to this would make that loss 11 kg.
Why is it that aerobic exercise does not seem great for weight loss? Well, one thing we know is that exercise can make people hungrier. It doesn’t take much in the way of additional intake to undo any ‘calorie deficit’ induced by exercise. That’s partly because, to be frank, exercise doesn’t burn massive amounts of calories (unless heroic levels of exercise are being performed). Then there’s also some thought that individuals who take more formal exercise may end up, quite naturally, being more sedentary at times when they are not exercising. Also, endurance exercise can increase the levels of hormones, notably cortisol, that may work to stimulate fat storage.
The generally poor weight loss results people get with aerobic exercise can cause despondency in some, and may increase the risk of people just becoming sedentary again. I suggest that knowing that aerobic exercise is not particularly effective for weight loss helps aligns expectations with results, which can actually enhance the chances of someone staying active.
When people are about to embark on an exercise regime that involves, say, brisk walking or running, I generally discourage thoughts about ‘burning calories’ and fat magically melting away. I do, however, encourage individuals to enjoy whatever it is they are doing and to revel in the health benefits, enhanced fitness and self of achievement additional exercise is likely to bring. For me, aerobic exercises are not really about weight control, but about being healthy and having fun.
References:
1. Friedenreich CM, et al. Adiposity changes after a 1-year aerobic exercise intervention among postmenopausal women: a randomized controlled trial. Int J Obes (Lond). 2011;35:427-435
2. Wu T, et al. Long-term effectiveness of diet-plus-exercise interventions vs diet-only interventions for weight loss: a meta-analysis. Obesity Reviews 2009;10:313-323
3. Shaw K, et al. Exercise for overweight or obesity. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD003817.
Tackle that Insulin Resistance and Zumba! My weight hasn’t gone down, but I can now get into jeans that haven’t fitted in years.
You may find this post interesting … makes some very good arguments on taking an ancestral approach to exercise: http://thehealthyskeptic.org/9-steps-to-perfect-health-7-move-like-your-ancestors
I’m getting ready to sign up for some high intensity strength training to support my weight loss. Will be interesting to see how it works, as I’ve already gone the chronic cardio route (I called it essentially “exercise bulemia”). Worked for a while, but it’s hard to sustain. I know I didn’t!
Beth
I’m growing increasingly interested in high intensity intermittent exercise and am planning a post on this soon.
Thanks for the link – that blog post looks very good.
John
Hi
I’ve been doing HIIT for some time now and highly recommend it. Great in the winter and / or when you really aren’t in the mood but nonetheless feel you really should do something. It can be done using whatever is your favourite exercise e.g running ( where it is / used to be called ‘fartleks’), exercise bike, rowing machine, whatever takes your fancy. Even Zumba I suppose ! 🙂 And the beauty of it is you get lots of benefit in only a little time per session. See: http://www.biomedcentral.com/1472-6823/9/3.
Dr Briffa
well said, its for “health not weight loss”, couldn’t agree more. There are however a large proportion of the population that do “heroic” type aerobic exercise.. 3hr cycles, 2hr runs etc. That works for weight loss. It also improves health physiologically, as you alluded to. Yet, there is a blanket statement made by some that “aerobic” exercise is bad for you, full stop. There is data on telemere shortening that would disprove this. There is also a huge amount of empirical evidence if you just look at those doing triathlons, ironman, marathons etc.
Maybe a seperate blog post, but have you seen the recent study on marathon runners by Dr.Siegal ?
I agree that a couple of gym sessions aren’t going to help weight loss – you just have to look a a machines calorie counter, but activity does seem to play a part based on a sample of one – me! I’ve never had a real weight problem, but before retiring my waist was up to 34 and my face a bit too full. Once retired and in a ‘house-husband’ role I returned to size 32 and generally thinned out. Food and drink intake more or less the same and the same two gym sessions a week.
The main difference that I can see was spending a lot more time on my feet doing low level physical activity, either in the house or out & about.
I get what you’re saying about aerobic exercise not creating ‘weight loss’. However, in your exapmle, the fact that the weight lost is fat is surely the most important part. Weight in itself isn’t a good measure of health is it?
What? These women exercised for a year and lost a kilogram of weight for every 86 hours they exercised? How much weight did they lose for the time they spent not exercising?
The crap argument that exercise is not an effective weight loss tool is a recycling of Gary Taubes’ silly statement that exercise only makes you hungry. I was amused – delighted, really – to see him go face-to-face on Larry King with Jillian Michaels (she is one of the trainers on the U.S. ‘Biggest Loser’ television show). She said to him that she’d be interested in talking about his success getting people to lose 100 pounds of weight without exercising (understood, of course, that Taubes would tell anyone to cut carbs to do that but it would take them years, not months, if they were successful at all). What did Taubes have as an answer to Michaels’ statement? Nothing. Just that glazed look (that you get while you wait for the people around you to keep talking and change the subject…) It was funny to see.
@ Kate – this is the same Jillian Michaels who endorses weight loss pills? The same woman who gets results by starving her Biggest Losers on low fat and having them work out for hours at a time? Those same biggest losers who then go on to gain the weight back because they haven’t learned how to eat healthily, who think whole grain cereals are a health food and think cardio exercise would work? I mean seriously, what sensible person gets a 400lb man to run on a treadmill – maybe she has shares in joint replacement companies too?
All that the interview with her and Taubes did was prove she has a bigger and faster mouth – probably high on those diet pills.